stereo net manual

8/10/2019 Stereo Net Manual

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PLEASE READ THIS PAGE

(yes, I know disclaimers are boring but)

Stereonet is distributed on an "as is" basis without any warranty, explicit or im-plicit. The author will not be liable for direct, indirect, incidental, or consequentialdamages resulting from any defect in this software or this user's manual. Furthermore,I make no systematic effort to inform all users of either bug fixes or upgrades. The pro-gram is upgraded periodically; write to me if you want to know the latest version.

I distribute the program Stereonet to non-commercial users without charge in theinterest in scientific communication (and because I don't want to have to worry aboutwhether a colleague pirated the program every time I see a plot produced by it in ajournal or at a meeting!). I grant my permission for non-commercial geoscientists todistribute the program and the user's manual to others, but only free of charge. Thisprogram may not be sold or offered as an inducement to buy any other product. Com-mercial users, please contact me for details.

I do not distribute copies of the source code in order to protect myself from un-authorized changes for which I might be blamed later. Please do not ask. If you havescientific questions about any of the procedures, I will provide copies of the individualsubroutines for your inspection.

I have tried to make the program as bug free as possible (after all, I use it for myown research), but errors may remain. I am always interested in errors people havefound or suggestions for improvement. Please write with your comments or sugges-tions. Thanks for your interest. I hope your find the program useful.

Rick Allmendinger

Dept. of Earth & Atmospheric SciencesSnee Hall, Cornell UniversityIthaca, NY 14853-1504

e-mail: [email protected]

Any product names used herein are copyright by their owners.

Stereonet v. 6.x for Macintosh was compiled by Absoft ProFortran v. 7 and is perma-nently linked to files which are copyrighted by Absoft Software. StereoWin v. 1.1 forWindows was compiled by Compaq Visual Fortran. Neither Absoft nor Compaq, how-

ever, is responsible for the performance of this software.


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Table of ContentsTABLE OF CONTENTS ...................................................................................................................................................3

OVERVIEW ........................................................................................................................................................................4

INTRODUCTION .................................................................................................................................................................4GENERAL ORGANIZATION ................................................................................................................................................4

Differences betweenMacand WindowsVersions ..................................................................................................... 5

User Interface.............................................................................................................................................................. 5

Data and Plot Files .....................................................................................................................................................6

HOW DATA ARE HANDLED IN THE PROGRAM .................................................................................................................7

DATA FORMAT..................................................................................................................................................................8

Lines: ........................................................................................................................................................................... 8

Planes: .........................................................................................................................................................................9

PLOTTING DIRECTLY IN LATITUDE AND LONGITUDE .................................................................................................... 10

MENU REFERENCE.......................................................................................................................................................12

THE FILE MENU .............................................................................................................................................................. 12

THE EDIT MENU.............................................................................................................................................................. 15

THE DATA MENU............................................................................................................................................................ 19

THE OPERATIONS MENU.................................................................................................................................................22

THE PLOT MENU ............................................................................................................................................................. 27

THE SYMBOLS MENU......................................................................................................................................................35

THE WINDOWS MENU.....................................................................................................................................................39

NOTES ON CONTOURING WITH STEREONET....................................................................................................40

ACKNOWLEDGMENT AND REFERENCING.........................................................................................................40

DISTRIBUTION POLICY ..............................................................................................................................................41

CREDITS ...........................................................................................................................................................................41

REFERENCES CITED....................................................................................................................................................42


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Overview

Introduction

This program was designed to accomplish most of the operations and plotting

normally needed by structural geologists and geophysicists dealing with orientation

data. The program, Stereonet, plots three-dimensional data on a lower hemisphere

projection.

Virtually all orientation data can be represented by two fundamental geometric

entities: Lines and Planes. Stereonet recognizes only data that can be input as either

one or the other. Three-dimensional shapes such as folds can be represented as a series

of planar elements, a standard practice in structural geology. Stereonet can perform

various operations on linear or planar orientation data, including:

Calculating poles to planes

Rotation of lines or planes

Constraining lines to lie on respective planes

Cylindrical best fit to a planar distribution, and

Conical best fit to a planar distribution.

It also produces various types of plots:

Scatter plots of linear data

Contour diagrams of linear data

Great circle plots of planar data

Plots viewed from any orientation, and

Plots of Latitude-Longitude data (e.g., digitized continental outlines) on theupper hemisphere

The plots produced by the program can be saved as standard graphics files for labeling

and printing by third party applications.

General OrganizationStereonet is organized around two data arraysone for Lines and one for

Planeseach of which can hold 2,500 individual measurements. The program can rec-

ognize four different lines formats, including latitude and longitude, and four different

planes formats. Lines can be treated as vectors (with directional significance as in pa-


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leocurrent directions or paleomagnetic vectors) or as axes (e.g., P and T axes of earth-

quakes). Data can be plotted either in the lower hemisphere (with positive plunges or

dips) or in the upper hemisphere (with negative plunges or dips). Latitude and longi-

tude data are always plotted on the upper hemisphere.

You enter these data into the program, either by entering one datum at a time in

a dialog box or by recording data in a standard ASCII text file and then reading the file

into the program. If you choose the latter method, the text file can only contain one data

type (i.e., lines or planes) in one data format. Stereonet can save data to disk in a variety

of formats, identified by writing a simple one-line header to the file that identifies both

the data type and format (details, below). The program can also read data files with no

identifying header information with additional input from the user.

Stereonet can (1) manipulate data (e.g., rotations, calculating planes from poles),

(2) calculate new entities from the entered data (e.g., determine the mean vector), and

(3) make a variety of plots from the entered data

Differences between Macand WindowsVersions

Both Stereonet for Macintosh and StereoWin for Windows follow the same orga-

nizational scheme, with only minor differences in menu structure and dialog box con-

tent. In the remainder of this manual, characteristics specific to Macintosh are shown in

red, and features or limitations specific to Windows are shown in blue.

User Interface

Both programs use standard graphical user interface elements to interact with

the user, including menus, windows, and dialog boxes.

Stereonet for Macintosh uses three separate windows: (1) a Plot Window where

your plot appears, (2) a Plot Record Window where a text record of what you plotted in

the Plot Window appears, and (3) a Data List Window where listings of your data or

data subsets appears. The Data List Window is hidden at start up but can be displayed

at any time using the Windows Menu. StereoWin uses just two children windows in-

side the main program window. Initially, the only one visible is the Plot Window on

which both the plot and the plot record appear side by side. Behind this window is the

Data List window. In either version, any windows can be brought to the front by


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choosing them in the windows menu. The plot in Stereonet/StereoWin responds to

mouse clicks in various ways. At any time you can (right) click inside the plot the trend

and plunge of the coordinate beneath the mouse will be displayed interactively. If you

are near a line that has been entered, its index number will also be shown. Several other

ways of interacting with the plot are described in the Menu Reference section of the

manual.

Menus are organized more-or-less according to Macintosh and Windows guide-

lines. The File Menu handles the input and output of data and plot files. The Edit

Menu has the standard editing commands (e.g., Undo, Copy, etc. note that these

commands work somewhat differently in StereoWin as described below) and prefer-

ences in it. The Data Menu contains items that allow you to manipulate, list, and sort

your data once you have entered them in the program. The Operations Menu is whereyou will find various routines for scientific calculations on your data (e.g. rotation, sta-

tistics, etc.); this menu, however, does not affect anything in the Plot Window at all but

several items will change the value of your data in various ways. For example, when

you rotate a set of lines, the new lines will overwrite the old lines in the lines array. The

Plot Menu causes things to be plotted in the corresponding window but none of the

items will affect the affect your data in any way. The items that control how the plot

will look are found in the Symbols Menu. Finally, the Windows Menu allows you to

show any of the windows that have been hidden for any reason.

You interact with and get feedback from Stereonet via dialog boxes. The Tab Key

will move you from one editable text field to the next and, in Windows, will also select

various controls like radio buttons, etc. StereoWin dialog boxes have a variety of

scrolling List Boxes and drop down combo boxes that Stereonet for Mac lacks.

Data and Plot Files

Stereonet uses two basic types of disk files. Data are stored on disk as a standard

ASCII text file. The program can read ASCII text files as long as they are in some con-

sistent, identifiable format, as described below. All word processors and spreadsheets

can read and save data in this format; many users have found it more convenient to re-

cord their data in a spreadsheet program and then save the spreadsheet as tab separated

columns for input into Stereonet. Data files are interchangeable between the Windows


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and Macintosh versions of the program with one caveat: In Macintosh, text files the end

of a line is identified by a carriage returnwhereas in Windows text files the end of a line

is identified by a carriage return and a line feed character. Thus to use files from one

platform on the other, you will first have to translate them, using any of a variety of

commercial and/or freeware tools (e.g., Excel, BBEdit Lite, MacLink, etc.).

In Stereonet for Macintosh, plot files are stored on disk as PICT files, a generic

type of object oriented (vector) graphics file that can be read by any commercial graph-

ics program. Likewise, you can use the system clipboard to copy Stereonet graphics as

PICTs for pasting into commercial graphics programs. PICTs of either the Plot Window

or the Plot Record Window can be saved/copied. Stereonet can also read and display in

the Plot Window PICT files saved on disk, either by Stereonet or by any other graphics

program. However, such PICTs are for display only or for use with Extract Data(Data Menu) and cannot be manipulated in any way.

StereoWin can save graphics to disk in two different formats: Using Save

Graphic in the File Menu, the entire contents of the Plot Window will be saved as a

.BMP file. This is a bitmap file at the resolution of the screen and is not suitable for pub-

lication quality graphics. For high quality graphics, one must Export a DXF file, a text

file in the AutoCad graphical exchange format. DXF files can be read by most graphic

programs (e.g., Corel Draw, Canvas) as vector graphics that can be printed at high

resolution. There are some minor limitations to this but none serious.

How Data Are Handled in the Program

While use of the program is largely self-explanatory, the user should be aware of

the way in which Stereonet manipulates data. The program operates on two basic ar-

rays: the first contains Trend and Plunge (T&P) data describing the orientation of a

group of lines, and the second contains Strike, Dip, and Dip direction (SD&D) data de-

scribing the orientations of a group of planes. The arrays will hold a maximum of 2500

lines and planes. Only one group of lines and one group of planes can be entered and

manipulated at any one time. Entering additional data will replace whatever was pre-

viously in the lines or planes arrays. Furthermore, certain operations will automatically

replace previous data in the arrays. For example, if one has entered a group of planes

and asks the program to calculate the poles to those planes, Stereonet will store the re-


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sulting poles in the lines array, replacing whatever was previously there. Other exam-

ples of this are noted below. One can think of a file of lines or planes as representing

data from one structural domain. For example, one would not want to mix fold axes

with poles to cleavage and plot them with the same symbol. Stereonet will plot multi-

ple data sets on a single diagram, but they must be entered one at a time, and each new

data set will replace the old one in the active array. For this reason, if you are using

Stereonet to enter data, be sure to save your data to disk immediately after entry and

before doing any analysis. Stereonet offers limited data editing functions. If you antici-

pate needing to do a lot of editing, I suggest that you do so in a spreadsheet or word

processor rather than in Stereonet.

Data Format

As noted above, Stereonet can recognize data in four different formats for lines

and four different formats for planes. If you are entering data in Stereonet, the format

used should be specified first in the Preferences dialog. If you have entered your data in

another program, Stereonet will be able to read the file without help if you provide the

two letter format code as the first line in your text document (listed in curly brackets,

below). Otherwise, Stereonet will ask for your help interpreting the format of the file, as

described in the Menu Reference/File Menu section of this manual. Individual numbers

and letters in a single line of data can be separated by commas, spaces, or tabs and the

numbers need not be formatted in any particular fashion.

Lines:

Trend, Plunge {TP} (e.g., 277 42). The trend value appears first, followed bythe plunge. A negative plunge indicates a vector pointing into the upperhemisphere.

Plunge, Trend {PT} (e.g., 42 277). The plunge value appears first, followed bythe trend.

Plunge, Quadrant {PQ} (e.g., 42 N 83 W). The plunge value appears first,followed by the trend, given in quadrant format. The trend must contain aletter (N, E, S, W), a number between 0 and 90, and another letter (N, E, S, W).

Latitude, Longitude {LL} (e.g., 41, -76). The latitude of the point appears first,followed by the Longitude. South latitude and west longitude are given asnegative numbers. See the following section for more information on Lati-tude-Longitude format.


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Planes:

Azimuth, dip, dip direction {AD} (ex. 320 25 W). Strike azimuth between 0and 360 is given first, followed by the dip magnitude, and then a letter speci-fying the quadrant (N, E, S, W) of the dip direction. This format is the one youwill see when you "List current data", even though input and output will be

in the format you specify. Azimuth, Dip {AZ} (ex. 140 25). This format assumes that the dip azimuth is

located clockwise from the strike azimuth. In other words, if you give a strikeof 137, Stereonet will assume that the dip azimuth is 227 (to the southwest).In this example, if your dip is to the northeast then you should specify a strikeazimuth of 317. This is actually the format that Stereonet uses for all of itsinternal calculations, even if you don't enter it that way.

Quadrant, Dip, Dip Direction {QD} (ex. N 40 W 25 W). In this format, you canreport any bearing with respect to N, S, E, or W. For example, the programwill correctly interpret W 50 N the same as N 40 W. Only the first letter issignificant for the compass directions (SW is interpreted as S). Data enteredin this format will be saved in the same format if you don't change the set-tings in the mean time. However, it may well not be in the identical form towhat you entered originally because the program will translate it into Azi-muth, Dip format and then on saving back into Quadrant format. Thus, ifyou enter N 77 W 30 W the program will save it as S 77 E 30 W (dip clockwisefrom strike).

Dip, Dip Azimuth {DD} (25 230). A format more commonly used in Europe.Note that the dip magnitude (vertical angle) comes before the dip azimuth.

Note that you can read data into the program in one format and save it in another.

Thus, you can use this utility to translated data files from one format to another. For

example, you can read data in Quadrant format, but save it to disk in the Azimuth for-

mat.

The preset formats are shown in the dialog box when you open it for the first

time. These are Trend, Plunge and Azimuth, Dip, Dip Direction. If you don't like my

preferences, you can save your own to disk by selecting the Save Preferences option in

the Data Menu. Stereonet will then save a file named "StereoPrefs" to disk in the same

folder as the main program. The next time you start up the program from the desktop,Stereonet automatically looks to see if there is a file named "StereoPrefs" on disk in the

same folder; if the file is found, the program will automatically use the format you

specified. If no such file exists, it will use my preset format.


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Data can also be entered as planes and Pitches (i.e., Rakes) of lines as follows:

Strike azimuth nearest the trend of the line (0-360), dip (0-90), dip direction (N, E, S, W),

and pitch (0-180). For example, if your plane is oriented 045, 50 E and your line has a

rake of 55 due east, you could enter that datum as either 045, 50 E Rake = 55 or as 225,

50 E, Rake = 125 (i.e., 180 55). Stereonet will immediately convert your input data to

Lines and Planes format and will not save the data in the Pitch format.

Plotting Directly in Latitude and Longitude

Most digital stereonets are cumbersome to use for plate tectonic type calculations

of, say, pole of rotation between to plates, because they work in terms of trends and

plunges of lines rather than latitudes and longitudes. This version of Stereonet now al-

lows you to enter lines in terms of latitude and longitude, by specifying that format in

the Preferences dialog as shown above. Note that you specify south latitude and west

longitude with minus signs. When Latitude and Longitude are selected, Stereonet

automatically treats the projection as an upper hemisphere projection:

Equal Area

Upper Hemisphere

Clicking the mouse inside of the stereonet will give you the coordinates in latitude and

longitude, although if you hold down the Shift Key it will show traditional trend and

plunge. When you do an operation like angle between two lines, the program will re-


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port the points clicked in Latitude and Longitude and will calculate the great circle dis-

tance, assuming an average Earth radius of 6378 km.

When you have selected Latitude and Longitude, Stereonet only shows those points

that are visible on the part of the globe that you are looking at.

When Latitude & Longitude is selected, the Set View Direction dialog box

changes to allow you to enter the view in terms of latitude and longitude. In this case,

the view direction will be situated in the middle of the globe and you will be looking

down on an upper hemisphere projection with the equator running from the left to the

right side of the plot. If your line type is specified as Latitude-Longitude (LL) and you

choose Scatter from the Plot Menu, Stereonet will ask you if you want to plot the sepa-

rate points or connected line segments. This enables you to, for example, enter the out-

line of continents as sequential latitude-longitude pairs. You can then rotate continents

around the globe, as shown for South America, below:

Equal AreaUpper Hemisphere


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Menu Reference

The File Menu

The File menu accomplishes the Input/Output of data. Using this menu, you tell

the program whether or not the data is on disk or will be entered in this session, that

you want to save the data, etc.

NewTo enter new data (i.e. that is not already stored on disk) in the program, select"New." A dialog box will appear, allowing you to choose a data type Lines,Planes, or Rakes because the program does not know in advance what format thedata will be in. If you have already entered some data, you will also be able to selectwhether or append the new data to that already existing in the program arrays orreplace those data. After the data type is chosen, Stereonet will show a dialog box,the exact format of which reflects the data format setting made in the Preferencesdialog box (Edit Menu).

OldSelect old if the data you want to enter is already on disk. First, the standardopen file dialog box will appear, asking you to choose the file that you want to read.If your data was saved with a first line header consisting of a two-letter code tellingthe program whether the data are lines or planes and what the data format is,Stereonet will read the file without any further input from you.

Stereonet can now read a wide variety of formats, as long as (a) a file contains onlylines or only planes, (b) each line of the file has data on only one orientation (exceptfor the first line, which can be a header), and (c) the entire file follows the same for-

matting convention. This allows you to save your data in a spreadsheet and justsave a copy of the spreadsheet as text. When you try to open a file which lacksStereonets two character format code in the first line, Stereonet now presents youwith the dialog box shown below:


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Although somewhat complicated, the use of the dialog is reasonably straightfor-ward. Stereonet can attempt to parse a file that has zero or more header lines at thebeginning of the file. Note that, with respect to column separator characters, Fortran,in which Stereonet is written, converts the Tab character to spaces on input, so

reading a tab-delimited file is identical to a space delimited file. Leading spaces in acolumn are always stripped before parsing, regardless of what separator characteryou use. However, spaces within a column are not stripped if the delimited charac-ter is a comma. Your first column of data does not have to be the first column in theline but, the first data column has to be the same in each line of the file, and eachdata column must be adjacent to another data column (i.e., no descriptive columnsin-between columns of data). This allows you to have a column of description eitherbefore or after the contiguous data columns but not in the middle of the data col-umns. Note that, if your description column precedes the data columns it must ei-


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ther (a) contain no spaces, or (b) use commas as column delimiters due to the limita-tion of Fortran regarding tabs. Stereonet simply ignores any columns following thedata columns and so you can use as many spaces as you want in those.

Underneath each of the Column labels, Stereonet shows you how it attempts toparse either the first or the second line of your file (depending on whether you have

specified the first line as a header or containing data). These change dynamically asyou change delimiter characters, number of columns of data, etc. It is still up to youto tell Stereonet what those numbers and letter mean by selecting the radio buttonsunderneath each column. The only potential ambiguity here is in using letters toidentify quadrants. If planes are selected and no quadrants are entered, a right handrule is assumed for the relation between strike and dip. If quadrant format is usedfor planes (QD in Stereonets two letter code), Stereonet will always expect to finda letter on either side of the column with the strike value and a letter to the right ofthe dip value (e.g., N 35 E 22 E and 22 E N 35 E are both interpretable) but othercombinations/conventions involving quadrants cannot be parsed. If Stereonet can-not determine your format or you have made inconsistent or incomplete entries inthe dialog box, you will be informed and Stereonet will leave the existing data in thelines and planes array untouched. All possible abuses of this dialog box have notbeen tested and there are quite likely combinations that will cause a crash! Saveearly and often! :-)

Once you have the input parameters set up, you can save a file to disk with formatdefinition. If Stereonet finds a file called FileFormatDef in the same folder as thedata that you are trying to import, Stereonet will ask you if you want to use thatformat definition. If you answer affirmative, Stereonet will attempt to parse the filewithout showing you the big dialog. Alternatively, you can click the Show dialogbutton and Stereonet with open the big dialog with the values from the file filled in.After you click Okay, if there are already data in the lines or planes arrays, youwill be presented with a dialog box asking if you want to append or replace the data

to that already in the program.Import PICTYou can import any PICT file into Stereonet's Plot Window with this

command. Practically, you will only want to import PICT's with stereonets on them!This is especially useful if you want to read in an existing plot to add more items toit. It is also invaluable in combination with the Extract Plot Data command in theData menu. You can, for example, scan a net in a published paper, import it withImport PICT, and then use the Extract Plot data command to convert it into ASCIItext files of lines and planes by clicking on the points and great circles. Be sure toobserve the following:

The scanned image or plot can have a rectangular outline without introducing anydistortion. The image can be of any resolution but, the higher the dpi, the morememory it will take. Stereonet will assume that the plot has North at the very top ofthe circle. If your scanned image is rotated, you should rotate it in a graphics pro-gram before reading it into Stereonet. There is no way to reposition or scale thegraphic once imported.

Stereonet has no way of knowing if your PICT has an equal area or angle plot in it soyou must select manually Equal Area or Equal Angle from the plot menu before you


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import the PICT.The Windows version will eventually be able to import .BMP filesbut cannot do so at present.

Save DataChoose this option to save your data. You will be asked to choose Lines,Planes, or Both in the dialog box that appears. The standard save file dialog box willthen appear, asking for you to name the file and choose the disk to save it on. The

data will be saved in the format specified in the Set Data Format dialog box (Fig. 1).The first line of the data will be the two-letter code identifying the data format.

Save PlotStereonet plots can be saved to disk as "PICT" files for printing. PICT filesare object-oriented graphics files of the type produced by MacDraw and most othergraphics programs and can be printed at high resolution by the Apple LaserWriterprinter. When you choose this option, you will get a dialog box asking you to namethe file (a suffix of ".PICT" is supplied but you don't have to use it). Whatever is inthe plot window when you choose this option will then be saved as a PICT file cre-ated by whatever program you choose in "Set File Formats" under the Data Menu.To open up the file after you exit just double click on its icon on the desk top and itwill be opened by your favorite graphics program.

You can still save the screen to disk as a bitmap file; use the key combination Com-mand-Shift-3 (hold all three down at once) will save the screen on disk as a filenamed "Picture 1", "Picture 2", etc. In MacOS X you can set a system preference forwhether such files are saved as TIFFs, PICTs, or GIFs.

In the Windows version, Save Plot will save the entire contents of the Plot Windowto disk as a .BMP file, with a resolution equivalent to that of the screen (nominally 96dpi). To get a higher resolution plot you must

Export DXFA DXF file is an ASCII text file in the AutoCad Graphical Exchange for-mat. This file can be read by most graphics programs (e.g., CorelDraw, Canvas, etc.),which will plot, and allow you to edit the individual plot elements as vectors. The

resolution of this file is identical to that of a Macintosh PICT file. There are certainlimitations to DXF files, the main one being that polygons cannot be filled, and thusthe result is not exactly WYSIWYG (what you see is what you get) but it is closeenough that it shouldnt be an undue burden to fix up in a graphics program.

Print PlotPrinting has been temporarily disabled in Stereonet v. 6.1.1 for Macintoshuntil I learn how to print in MacOS X. Apple introduced significant changes to theseAPIs with the CarbonLib and the printing that used to work is now broken. You canprint at the resolution of the Screen in StereoWin. For better resolution, export yourplot as DXF and print it from within a commercial graphics program.

Quitor ExitUse this to leave Stereonet and return to the Finder. Stereonet will ask ifyou want to save any unsaved data before quitting, but it will not prompt you to

save the plot.

The Edit Menu

UndoThis allows you to undo the most recent plot and revert to the previous version.If you select Undo two times in a row, it will act like a redo feature (i.e. restoring theoriginal plot) the second time around. Note that Undo only works with the plots inthe plot window; it has no effect on any operations that were performed on the linesor planes arrays. For example, you cannot undo the calculation of poles to planes


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and restore whatever was previously in the lines array. This choice is currently dis-abled in StereoWin.

Select TextThis command works only in the List Window of StereoWin. It will allowyou to select text in that window with an I-beam cursor. In StereoWin, you mustselect the text before you can copy it to the System clipboard. Text copied in this way

can be pasted as fully editable text in any appropriate application.Select GraphicsBefore you can copy any graphics in the Plot Window of StereoWin,

you must select them first by choosing this menu command and then dragging aselection rectangle across the part of the screen that you want copied. In certain ver-sions of Windows, the selection rectangle may not show up on screen but the areathat you drag across will nonetheless be copied when you subsequently chooseCopy, below.

Select AllYou can select the entire Plot Window or the entire contents of the ListWindow with this command; no dragging necessary. Note that once you choose any ofthese three Windows Select commands you mustsubsequently choose Copy beforeyou can do anything else in the program.

CopyCopy works on either the Plot Record Windowor the Plot Window (whicheveris in front) and copies the contents of the window to the clipboard. The window it-self is unaffected by the command. The graphical format copied to the clipboard inMacintosh is PICT vector graphics. In Windows the text is copied as editable textand graphics are copied as BMP format.

ClearThis command will erase both the Plot Record Window and the Plot Window,without copying either to the clipboard. This is the fastest way of erasing the plotwindow when you want to start over with a blank plot. The command can be re-voked by choosing Undo. StereoWin does not currently have a Clear commandbut will in subsequent versions.

Edit DataYou can interactively edit the data in the lines or planes arrays using theEdit Data dialog box (Figure 2), accessed under the Edit Menu (control-U). Youmust type the number of the datum you wish to edit into the box and the trend andplunge or strike and dip will appear in two editable text boxes below. For informa-tion purposes, the dialog box also displays the direction cosines of the datum se-lected. You can also enter new data using the Add button (new data are alwaysadded at the end of the array) or delete data using the Delete button. If you use theEdit Data dialog box and click Okay to close it, the status of the data will be set toUntitled and Unsaved and any lines and/or planes subset you have set up will bereset to the entire data set (even if you have made no changes). The format of theEdit Data dialog in Macintosh is different than in Windows. In the former, you musttype the number of the datum you wish to edit, whereas in the latter you need onlyselect it from a scrolling list that shows all of your data, as shown below:


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PreferencesIn Preferences, you set the format of the Lines and Planes data as well asseveral other features related to the general operation of the program. You can selectonly one lines format and one planes format at any particular time. The two letterheader code that Stereonet places in the first line of each data file is shown in squarebrackets just to the right of the name, followed by an example of the format in pa-rentheses. Note that choosing Latitude, Longitude for a data format will automati-cally force Stereonet to produce upper hemisphere plots. The formats that you selectwill determine the exact layout of the dialog boxes used to enter new data.

In the Mac version, you can enter the four letter Creator Code to have your favor-ite graphics program open the PICT files that you save. The Mac version also allows


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you to specify that white space be plotted behind points. Checking Save all currentsettings has the same effect as choosing Save Preferences from the Edit Menu.

To turn on or off the light gray grid that the program draws inside the stereonet,check, or uncheck, Show grid backdrop. You can select whether the grid lines aredrawn every 2 or every 10.

If you check Automatically plot newly opened/entered data files, Stereonet willautomatically make a scatter plot of each new lines file or a great circle plot of eachnew planes file as soon as you enter it from the Open command in the File Menu.You will still have to click a dialog asking whether this is a new plot or old ( except ifyou hold down the Shift Key in the Mac version).

Save PreferencesYou can save all parameters of the program (about 20 in all) to diskin a file called StereoPrefs. Set every thing as you want it (e.g. equal area or angle,data format, point size and shape, show number, colors, etc.), then choose Save Pref-erences from the Data Menu to save StereoPrefs. The next time that Stereonet opens,it will look for this file in the same folder as the program itself. If program finds thefile, it will set your previously selected preferences; otherwise it will use my pre-ferred defaults. Note that the file StereoPrefs can be opened and edited by any wordprocessor capable of reading an ASCII text file but I do not recommend that you dothis because you can easily enter an incorrect value that may cause the program tobomb. If this happens, you should throw out the old StereoPrefs file and save a new


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one from within Stereonet. Although data files are interchangeable between Macand Windows versions, Preferences files are not!

The Data Menu

Data Countwill display a dialog box showing the total number of lines and planesentered, as well as the number of lines and planes in the active subsets. This com-mand allows you to see the name of the disk files input to the line and planes arrays,as well as to see if the data in those arrays have been saved or not. Data entered as"New," or recalculated using one of the commands under Operations menu will belisted as "Untitled and unsaved." If you save the data to disk and then choose thisoption, you will see the new file name.

List Current Datawill show and type into the "Data List" Window the contents of thecurrent lines and planes subsets (not the total data entered). In StereoWin, the DataList Window can show a maximum of 100 lines and planes; if you have enteredmore than that, a dialog box will appear asking you to specify a range to display. InStereonet, the entire data set is shown but to scroll the display to see it all you mustclick and drag down (or up). In both, the data that are Hidden are displayed inlight gray.

As you can see in the screen shots from StereoWin, when you have entered data asLatitude, Longitude, the equivalent upper hemisphere trends and plunges are alsoshown.

Define Data SubsetsStereonet will allow you to define a subset of the total data en-tered. After you select the subset, all subsequent operations and plotting will apply


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only to that subset. The lines subset does not have to be the same as the planes sub-set.

Reset to Total DataSelect this command to have the program forget any data subsetsthat you may have established with the previous command.

Lasso DataWhen you choose this option from the Data Menu, you will be instructed

to use the mouse to circle the data points (i.e. lines) of interest in the plot window.You can do this even if no lines are plotted, as long as some lines have been entered,but obviously it is easier if you make a scatter plot of the lines first. If you have al-ready specified a lines data subset, the lasso will only find the lines in the subset.Once you have selected the lines, a dialog box will present you with three choices:(1) List the lines in the Data Window. The number to the left of the line trend andplunge shows its actual position in the data set. (2) Save the selected lines to disk ina new data file. You will see the standard save file dialog box. (3) Delete the linesfrom memory. This option only affects the lines in memory but has no effect on anydisk files. Once you choose this option all of the remaining lines will be renumberedand any data subsets will be reset to the total remaining population. This optiondoes not affect the Plot Window. To get rid of the deleted points on the screen, you

must replot your data.Show or Hide DataAlthough StereoWin does not have a lasso function, a similar type

of data sorting can be achieved using this command. A dialog box will be displayed(below) showing all of the entered lines and planes in two scrolling list boxes. Youcan select multiple lines by clicking repeated (no shift click is necessary). Once youhave selected all of the lines that you want to hide, click on the Hide radio button tomark the selected lines as Hidden. Hidden lines will show up in data lists in lightgray color, but will not be included in any plot or analysis until they are unhidden.


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Extract Plot DataChoosing this option allows you to convert mouse clicks in the PlotWindow into data points in the lines and planes arrays. You will probably use thisfeature to extract data from old files (or scans of figures in journal articles publishedby others) for which you not longer have (or never had) the ASCII text files. Ex-tracting the data is a four step process:

1.

First, you must import a PICT using the Import PICT command under the FileMenu. The PICT file can contain either vectorized graphics (like the PICT file

that Stereonet saves when you choose "Save Plot") or a bit map (which is whatyou get when you scan data on a scanner).

2.

Next choose Extract Plot Data. The first thing you will be asked to do is definethe outer circle of the imported stereonet by clicking on three points on theprimitive. As soon as you depress the mouse button for the third point, Stereonetdraws a circle which resizes itself automatically until you release the button, al-lowing you to fine tune your selection. Note that Stereonet automatically as-sumes that North is at the very top of the imported projection. For importedPICTs with north at a different position, just do a vertical axis rotation after ex-tracting all the data.

3.

Then you just click on the points to extract line data or click at two different spotson great circle traces to extract planes. Stereonet marks your clicks with a red Xand makes an audible click so you can see if you have already extracted a pointor not.

4.

Finally, you must click the mouse outside of the net to end the data extraction.Note that the data that you extract will replace whatever was previously in thelines and planes array!!


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Steps one and two, above, will cause Stereonet to reset the radius of the projectionbut does not reset the center of the projection for subsequent plotting. Any addi-tional plotting will continue to use the reset radius, which may cause problems incontouring if you do not first reset the radius using the change net command in theplot menu. This is because only certain net radius' work with Stereonet's 21 x 21contour grid and 3 x 3 pixel pattern box size. If this happens to you just select theChange Net Radius command under the plot menu, enter whatever value you wantand Stereonet will rescale the net to the closest acceptable radius. Then just re-contour the plot.

Stereonet has no way of knowing if your PICT has an equal area or angle plot in it soyou must select manually Equal Area or Equal Angle from the plot menu before youimport the PICT.

Add Data ManuallyThis option enables you to add data to your plot by clicking themouse within the primitive of the stereonet. The orientation of the point is shown inthe upper right hand corner of the window. The point is recorded and marked with a redX when you release the mouse button. The data entered this way can either be ap-

pended to or replace any data already entered in the program.StereoWin will eventually have both extract data and add data manually functionsbut it does not have them at present.

The Operations Menu

The various options in the Operations menu make calculations on the data in the

current arrays but do no plotting. Many of these options will change the data in one or the

other of the two arrays, so careful attention should be paid to the sequence in which you

do calculations and plotting of multiple data sets.

Polescalculates the lower hemisphere poles (line perpendicular to a plane) to theplanes stored in the active planes array and places the resulting lines in the activelines array. This requires no input from the user (except of course the originalplanes).

Planes from PolesCalculates the planes that are oriented at 90 to the lines in the Linesarray (i.e. it assumes the Lines are Poles and calculates the corresponding Planes).The result of this calculation is stored in the active Planes array, replacing whateverwas in it before. This requires no input from the user.

Rotate DataA dialog box will appear, asking you to choose Lines, Planes, or Both(Figure 6). The data type that you choose will then be rotated about an axis with anyorientation and in any amount. In the same dialog box, you enter three values thatdefine the Rotation. The rotation is always in a clockwise sense (i.e. right hand rule)looking in the direction of the given azimuth of the rotation axis (in the figure below,because the magnitude of rotation is a negative number, the rotation will be coun-terclockwise looking toward azimuth 035). After the calculations are complete, thenew lines and/or planes are stored in the active arrays (for plotting, saving, etc.) andthe old data are wiped out.


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You can rotate data either as axes or as vectors, depending on whether or not theTreat data as VECTORS not axes box is checked (see below). Data treated as axeswill always be converted to lower hemisphere lines whereas data treated as vectorscan be rotated into the upper hemisphere. Vectors that point into the upper hemi-sphere will have negative plunges.

Variable RotationYou can now rotate a single array of lines and/or planes dataabout variable axes by choosing Variable Rotation under the operations menu. Thisoption would allow you to, for example, unfold lineations by rotating the accompa-nying bedding back to horizontal, etc.

Two types of rotations are possible (following figure): (1) data can be unfolded byrotating the corresponding bedding planes back to horizontal (a rotation equal to thenegative of the dip about a horizontal axis the same as the strike azimuth), or (2)

variable rotation axes can be specified.There are two choices for unfolding bedding: you can use the planes currently inmemory in the planes array, or you can temporarily read planes data from a TEXTfile on disk. The data for the Variable rotation option is always read as a TEXT fileon disk. The disk file is read in temporarily at the time of the rotation; it does notreplace either the line or the planes file. The rotation axes or bedding orientations inthat file (or in the planes array) should correspond one-to-one with the data to berotated in the lines and/or planes arrays. If subsets of the lines and/or planes ar-rays have been defined (from the Data menu) and the bedding/rotation axes (B/RA)file has as many or more data as the lines and/or planes, then the same subset of theB/RA will be used for the rotation. For example, if the lines array has 20 measure-ments in it and a subset of 6 - 12 has been defined, beds 6 - 12 of the B/RA file willbe used for the rotation (assuming that the latter has 20 or more values in it). If theB/RA file has fewer measurements in it than the total number of measurements inthe lines or planes array, then the current subset will be rotated one-for-one with thevalues in the B/RA file until the end of the B/RA file is reached. Then, all remain-ing values in lines and/or planes will be rotated using the last value in the B/RAfile. If you are unfolding data, you should correct for fold plunge before choosingthis option.


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For unfolding about bedding, any common planes file format saved normally byStereonet can be read in for the rotation. For Variable Rotation about horizontal

axes, any file in the planes format can also be read in. In this case, the strike azimuthdefines the azimuth of the rotation axis and the dip defines a positive (right hand)rotation about that axis. This is just the opposite of unfolding bedding (where thedip defines a negative rotation about the strike, because of the right hand rule forstrikes). For variable rotations about plunging axes, the text file must be created inEdit or some word processing program with the following format: The first line hasthe letters VR which tell Stereonet that it is a variable rotation. Each subsequent linehas one rotation axis defined by three numbers: Azimuth of axis, plunge of axis,and amount of rotation. As with Rotate Data, a positive rotation is right-handedlooking in the direction of the given azimuth.

Line on PlaneSmall errors in the collection of field data often result from independ-

ent measurement of planes and lines lying on those planes (e.g. slickensides on faultsurfaces, or fold axes on axial surfaces, etc.). This operation recalculates the posi-tions of lines so that they lie on their respective planes. To work, there must be anequal number of lines and planes in the two arrays and the elements in the two ar-rays must correspond (i.e. the first line in the line array must correspond to the firstplane in the plane array). This operation assumes that the plane was correctlymeasured and recalculates either the Trend or the Plunge of the line; the one it se-lects is that which produces the smallest change in the orientation of the line. Forexample, if it calculates that the plunge should be changed by 5 (keeping the trendthe same) or the trend should be changed by 7 (holding the plunge the same),Stereonet will change the plunge. No error checking is done by the program. Forexample, if a given plunge is steeper than a given dip (an impossible situation, butone which is not uncommon when the plane has a gentle dip), Stereonet automati-cally assumes that the plunge is in error and recalculates it. This operation requiresno additional input from the user.

Fisher Vector DistributionCalculates the Fisher distribution mean vector of the linesin the lines array and displays the result in a dialog box. All lines are treated asvectors pointing downward into the lower hemisphere, unless they have negativeplunges (see discussion of Plot Mean Vector under the Plot Menu). Thus a line that


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plunges slightly east will nearly cancel out a line that plunges slightly in the oppo-site direction (i.e. west). To get a mean pole for axial data (i.e. lines with no direc-tional significance), you should use the Bingham Axial distribution, which is de-scribed in the next section. See Ramsay (1967) p. 15-17, Fisher et al. (1987), orCheeney (1983) p. 110-119 for description of method. This option produces nochanges to the lines in the lines array.

Bingham Axial DistributionThe Bingham distribution is the statistical analysis ofchoice for orientation of linear data when the lines have no directional significance(in contrast to vector data). This routine calculates a symmetric matrix consisting ofthe sums of the squares and of the products of the direction cosines for each line inthe lines array. The eigenvalues and corresponding eigenvectors are then calcu-lated. The eigenvalues, normalized to 1, give a measure of the relative concentrationof points. In general, a point concentration will have one large eigenvalue and twomuch smaller ones. A girdle concentration will have two large and equal eigenval-ues and one much smaller one (the eigenvector of the latter corresponding, for ex-ample, to the fold axis when the lines are poles to bedding planes). The programalso calculates the 95% confidence "ellipses" (because of the orthorhombic symmetryof the Bingham distribution) using the algorithm of Fisher et al. (1987) but does notplot them. Finally, a uniform distribution will have three approximately equivalenteigenvalues. This routine produces no change to the lines or planes array, and doesno plotting in the "Plot" window.

Angle Between Two LinesThis choice allows you to use the mouse to select any twopoints in the "Plot" window to determine the angle between the corresponding lines.Instructions are typed into the "Data Entry" window. Following selection of the sec-ond point, the acute and obtuse angles between the two lines and the trend andplunge of the two lines selected appear in the "Data Entry" window. As you holddown the mouse button and move it around inside the stereonet, the trend andplunge of the line is interactively displayed in the upper right hand corner of the

Plot Window. If you are choosing the second line, the angle between it and the firstline are also shown.

While selecting the two lines on the screen,

Stereonet animates the selection by showing

both the points and the great circle through

them along which the angle is measured.

When you release the mouse for a second

time, the results are shown in a dialog box as

below.


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The precise angle between any two lines in the lines can now be determined in adialog box (Figure 8) by holding down the shift key while choosing Angle BetweenTwo Lines. The lines can be any two in the Lines array, two user entered lines or acombination of data in memory and entered in the dialog box. For the latter, firstchoose In memory and the value of the lines will be entered in the trend and plungeboxes. Then, click on User entered and enter your line in the other trend and plungebox.

Angle Between Two PlanesThe dialog box for Angle Between Two Planes worksidentically to the previous menu choice, except that strikes and dips are enteredand/or displayed in the boxes (strikes entered only with right hand rule).

Intersection of Two PlanesYou can use this dialog box to calculate the precise inter-section of two planes, either both in memory, entered manually, or a combination ofthe two. The dialog box is shown in Figure 9.

Apparent DipThe "Apparent Dip" command under the "Operations" menu will bringup the Apparent Dip calculator dialog box (Fig. 10). In this box, you can

1.

enter the strike and dip of a plane and calculate plunges of two different lineswith known trends in the plane

2. enter the trend and plunge of two lines and have the program calculate the planethat contains them

3.

enter a strike and a single line (i.e. apparent dip) and have the program calculatethe dip of the plane

4.

enter a strike and dip and the pitch of one or two lines and have the computercalculate the trends and plunges of the one or two corresponding lines.

The user identifies which data are being entered by checking the boxes to the left ofthe label. Strike and dip are specified using only the right-hand rule (i.e. where thedip direction is clockwise from the given strike azimuth). Once sufficient informa-tion has been entered, the program will automatically fill in the remaining boxes.You will not be able to check or change the entries in those boxes. If you click on abox that is already checked, the program will assume that you want to start over andwill erase all of the entries in the dialog box. Note that, when you specify a strikeand dip and a plunge of a line, there are two possible lines with that plunge. Theprogram will calculate both and will display the second line in the section of thedialog box marked "--Line 2--".


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The Plot Menu

Plot produces the diagrams of various types in the "Plot" window. None of the

options produces any change in the active lines and planes arrays.

A neat feature of the "Plot" window is that, at anytime, you can point and click

the mouse at any point in the projection and Stereonet will record the Trend and Plunge

of the corresponding line in the upper right hand corner of the Plot window (trend al-

ways before plunge). You can move the mouse around with the button held down and

see the T&P values change as you go. When you click on a line, the number of the line

in the data array will be displayed. If you click the mouse outside the boundaries of the

projection, the program does nothing. This feature can be used to find out the line of

intersection of two planes (after plotting the planes, of course) or apparent dips along a

plane, etc.

Equal AreaWhen this option is chosen, the plot will be an equal area projection; thisis the preset condition when you open up the program. The type of projection isprinted in the upper left corner of the Plot Window for reference.

Equal AngleStereonet can also make plots using an equal angle projection. You canonly use Equal Area or Equal Angle on a single plot, not both. If you were in EqualArea and you chose this option, an alert box will appear asking you if you want toGo Ahead or Cancel.

In the apparent dip calculator, you

must check the boxes to the left ofthe numbers you are entering. The

rest of the boxes are filled in when

you click the calculate button. In this

example, note that Line 1 has a

negative plunge. This means that the

line points up into the air and wouldplot in the upper hemisphere.


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Change Net RadiusWhen you start Stereonet, the projection displayed in the PlotWindow has a radius of 192 pixels. The size of the net can be changed at any time,either before or after plotting, using this command. The size of the net can now bespecified to the pixel. [However, if you are using contour patterns rather than lines,you are still limited to even multiples of the contour grid spacing as previously (seebelow).]This allows you to set the radius to print the nets at any size you want. Astereonet prints at 72 pixels per inch. Therefore if you want an 8" in diameter (4 inchradius) net, you simply set the net radius to 72*4 = 288 pixels. If you want a 15 cmdiameter net, you set the radius to 72*(7.5 cm)/(2.54 cm/in) = 213 pixels [note thatyou must choose the nearest integer value; the program will crash if you enter a realnumber]. Changing the net radius will cause the current plot to be erased!

Set View DirectionStructural geologists are accustomed to viewing the stereonet as alower hemisphere projection, as if one were looking vertically downward. How-ever, there are many times when a different frame of reference is better. For exam-ple, you may want to plot data in the plane of a cross section (a view direction whichis horizontal and perpendicular to the azimuth of the cross section), or in the profileplane (down plunge view) of a cylindrical fold (a view direction parallel to the foldaxis). Of course, you can do this by rotating all your data, but it can be a bit tedious,and you dont have and visualization aids. Stereonet now allows you to set any viewdirection without having to rotate all of your data. Because of the potential unfa-miliarity of this new option, I describe it in detail here.

When you choose Set View Direction under the plot menu, the above dialog boxwill appear. The trend and plunge that you enter in this dialog will become the new

center of the projection and the primitive plane perpendicular to that direction. Aswarned in the dialog box, your current plot will be erased and you will have to re-plot everything. You can easily return to the default view of North-East-Down byclicking the Default View button in the set view dialog box. You do not need toenter any values first. The following diagram shows the relationship between theCartesian coordinates of a normal geographic stereographic projection (in black) andthose of the new view (in red).


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The new view coordinate system axes are plotted at the same position as the oldaxes. For example, the new X3is plotted in the center of the net at the same place as

the old X3. Stereonet actually maintains your data in the format of the new coordi-nate system (view coordinates) in memory to speed up operations, but transformsthe data back into geographic coordinates whenever it reports the results of a calcu-lation, and before saving to disk, etc.

To maintain a sense of orientation, I highly recommend that you have Show Gridturned on in Preferences; Stereonet will then plot the rotated grid, with the great cir-cles intersecting at the north or south pole. This essentially lets you see both coordi-nate systems at once. For the values shown in the above dialog, the rotated grid withthe new and old coordinate systems, is shown below. Note that for the entered val-ues, X1, X2, and X3are all positive, but other view directions can result in negativeaxes being plotted.

Equal AreaX1

X2

view directionX3

Northor South

(X1orX1) Eastor West

(X2orX2)horizon

Downor Up(X3orX3)

This diagram shows the relation-

ship between the two coordinate

systems used when you set the

view direction. The default view

orientation is shown in black and is

labeled with the unprimed Xs. An

arbitrary new view is shown in redwith axes labeled with X. This dia-

gram is for a typical transformation.

A slightly different one is used

when latitude-longitude data havebeen entered.

Example of a rotated view direction

with a trend of 045 and a plunge

of 37. This vector constitutes co-

incides with the center of the

stereonet and is the X3 axis. The

primitive of the stereonet in this

view corresponds to a plane strik-

ing 135 and dipping 53 to SW.

The light gray grid still corresponds

to the geographic coordinate sys-tem.


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When you click and hold down the mouse on the stereonet, the orientation that yousee is in geographic coordinates. That is, if you click on the pole in the above dia-gram, the trend and plunge will show T&P = 0, 0, or perhaps T&P = 360, 0. Thisis the fastest way to determine whether or not the pole showing is north or south(the latter, of course, will have a trend of 180). Clicking on points above the horizonwill show negative plunges, because these points are plunging upwards into theupper hemisphere, negative by standard structural convention. If you hold downthe shift key while you click on the stereonet, you will see the trend and plunge ofthe clicked point in the new view coordinate system. It is unlikely that you will needthis very often!

One potentially confusing aspect of this new capability is the concept of upperand lower hemispheres. Once you set the view direction, the upper hemisphere isthe one in the direction opposite to the direction in which you are looking. Lines thatplunge downward geographically (and thus have positive plunges) may well endup in the upper hemisphere of the new view. When you choose Scatter or MeanVector, Stereonet will ask you how you want to handle these upper hemispherelines. The figure below shows the same data set plotted in geographic coordinates(left) and with a view direction of 045, 37. Note that some of the lines have becomeupper hemisphere (to the new view direction) because of the coordinate transfor-mation:

Equal Area

N = 70

"upper" hemispherelines plotted in

"lower" hemisphere

Equal Area

N = 70

ScatterThis option produces a scatter plot (point plot) of the lines in the current linesarray. Stereonet will first ask if this is a New Plot or an Old Plot in a dialog box; ifyou answer New Plot, the "Plot" window will be erased and the border of the pro-jection redrawn before plotting. Pressing Return selects the default, Old Plot, andwill leave the existing plot intact and will plot the points on top of it. Thus you can


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plot multiple data sets on the same diagram. Scatter uses variations on four differ-ent point symbols: circle, box, triangle, and diamond. These symbols can be plottedwith three different types of fill (black, gray, or white), at a wide variety of sizes, andwith any color your computer is capable of plotting. These options are selected inthe Symbols Menu. Once the point symbol characteristics of a line are selected, alllines plotted with Scatter will have the same characteristics until you redefine thelines symbol.

Whenever you ask for a Scatter plot, the program will scan the file of lines for ori-entations with negative plunges (indicating lines which plunge into the upper hemi-sphere). If it finds any, you will see the above dialog box, which asks you how todisplay those negative plunges. This first choice is self-explanatory. In the secondchoice, if you select a different symbol then what you get depends on what has beenselected in the symbols menu. The lower hemisphere lines are always displayedwith the selected symbol (including size and shading). The point characteristics forthe upper hemisphere lines are selected in the same menu:

Great CirclePlanes can be plotted as great circles using this option. Stereonet will firstask if this is a New Plot or an Old Plot in a dialog box; if you answer New Plot, the

"Plot" window will be erased and the border of the projection redrawn before plot-ting. Pressing Return selects the default, Old Plot, and will leave the existing plotintact and will plot the points on top of it. Thus, you can plot multiple data sets onthe same diagram. Great circles are plotted according to the pen style style, size,and color in the options accessed from the Symbols menu; the default is a solid lineone pixel wide. StereoWin cannot plot lines heavier than one pixel.

Kamb ContourContour produces a contoured diagram of the lines in the lines arrayusing the method of Kamb (1959). This method uses a variable area counting circle


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and calculates the number of standard deviations ("") from a uniform distributionof points on the projection. The resulting plot shows contours of point density withthe lowest contour having a value of 2and 3the default value of a uniform distri-bution (this can be changed with the Contour Parameters dialog box). The contourcounting grid has been increased from 17x17 to 21x21, providing somewhat in-creased resolution on the contours.

Contours are now drawn as unfilled continuous polygons by default. These can befilled with the patterns or colors of your choice in your favorite graphics program.You can now contour multiple data sets on the same diagram. The color of the con-tour lines is specified in the Symbols Menu. The old style patterns are still available.Contour Lines and Patterns are turned on and off using the "Contour Parameters"command under the symbols menu. It is possible to plot both contour patterns andcontour lines on a plot, but be aware that these two commands use slightly differentalgorithms so the boundaries of the fields are close but do not always coincide ex-actly. If the difference between the two algorithms is important to you, then you areprobably up to no good anyway! Contour patterns still cause the existing plot to beerased. Furthermore, because I am still using the old way of painting contours to thescreen, the net radius of your plot will be rescaled to the nearest even multiple of 30.Contour lines can be plotted on top of an existing plot and do not change the net ra-dius. Contour patterns are now saved to PICT file (or the clipboard) just as thou-sands of little rectangles. It is no longer possible to save them as bitmaps. I suggestusing the patterns for screen display, but lines for printed output. To show thecounting grid and the individual numbers at each node, hold down the shift keywhile choosing either of the two contour options in the plot menu.

If you hold down the Shift key while you select either Kamb or 1% area contouring,the grid used with the number of counts at each node will be displayed prior tocontouring. After you have looked at the grid, you will have to press the Return keyto continue the contouring process.

For a more in depth discussion of how the program does the contouring, see thesection entitled "Notes on Contouring" at the end of the manual.

1% Area ContourStereonet also allows contouring using the more classical andwidely used 1% area method, where the counting circle is automatically constrainedto be 1% of the total net area. As in the Kamb method, above, you can set the con-tour interval to whatever value you want (e.g. 0.5, 2.7, etc.). As above contouringwill always erase whatever was previously on the net.

Rose DiagramThis selection will make a rose petal diagram of either the trends oflines in the line array or the strikes of planes in the planes array. Dips or plunges areignored. Petal width can be set at the time of plotting to 5, 10, or 20 increments.

The length of a petal is calculated as the percentage of the total number of datapoints that fall within the selected width bin. You set the value of the outer perime-ter of the plot (in percentage of total data set) and Stereonet scales the petals to thatinput value. This gives you the option to plot single data sets as large as possible orto plot multiple data sets with the same outer perimeter. Stereonet tells you theminimum value for the outer perimeter that can be chosen so that the petals do notexceed the size of the plot. Following plotting of the diagram the maximum petalsize in percent and the 10 azimuthal increments are printed in the Data Entry Win-


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dow. The outer perimeter of the Rose Diagram is the same size as the stereonet andthus the orientation of lines or planes can be plotted on top of the rose petals if de-sired.

Pick Great CircleWith this option, you can use the mouse to pick the orientation of agreat circle and plot it on the net; it does not change the values in either the Lines or

the Planes arrays. There are two ways to pick a great circle: In the default method,press and hold down the mouse button inside the net; that point is the pole to theflashing great circle that appears. As you move the mouse around the screen, thegreat circle will change accordingly. When you release the mouse button, the greatcircle becomes part of your diagram. Alternatively, you can press the Shift keywhile choosing Pick Great Circle. Then the great circle is defined by clicking anytwo points on the net. A great circle will be drawn through those two points and asolid square will be plotted at the pole to the great circle. The orientations of thegreat circle and the pole, as well the orientations of the two points selected, will beprinted in the "Plot Record" window. With either method, the trend and plunge ofthe line at the point of the mouse cursor (the pole in the first method) will be dis-played interactively in the upper right hand corner of the Plot Window, along withthe orientation of the great circle as long as you hold the mouse button down.

This option is very useful for estimating a best-fit great circle to poles to bedding toget a fold axis. It can also be used to pick perpendicular nodal planes for earthquakefocal mechanism or structural analysis. Select the first plane, then choose Pick GreatCircle again and select your second plane, making sure that one of the two pointsselected is the pole to the first great circle.

Plot Small CircleYou can plot small circles in either Equal Angle or Equal Areamode. A dialog box will appear, asking you for the position of the center of thesmall circle (entered as a trend and plunge) and its radius in degrees. If the small cir-cle intersects the primitive of the net, you will be asked whether you want to plot the

remaining part of the small circle in the upper or lower hemisphere. Note that, un-like an analog (i.e., paper) stereonet where the center of the small circle must coin-cide with the north or south pole of the grid, the digital stereonet can plot a smallcircle in any orientation, making all those drill hole problems a whole lot easier :- )!

Plot PointAt any time, you can tell Stereonet to plot a point that is not in the currentlines array by choosing this menu option. A dialog box will appear. In addition tospecifying the orientation of the line, you can also choose between a box and a circleand you can specify the size of the point. The point will be drawn with the colorsthat have been chosen using the Set Color submenu in the Symbols Menu.


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Cylindrical Best FitThis option will calculate a best-fit plane to a distribution of linesand will plot the plane and the pole to the plane in the "Plot" window and the ori-entations of the two in the "Plot Record" window. The calculations do not affect ei-

ther the lines or the planes arrays. This can be used to find the cylindrical fold axisfrom bedding pole data (Figure 20) or the true strike and dip of a plane from twoapparent dips. This routine calculates the Bingham distribution and displays the ei-genvalues and eigenvectors both on the plot and numerically in the "Plot Record"window (see discussion under Bingham Axial Distribution). The great circle isdrawn through the two eigenvectors corresponding to the two largest eigenvalues,with the fold axis given by the vector corresponding to the smallest eigenvalue.

Conical Best Fitdoes the same thing as the previous option except that it calculatesthe best-fit cone to a distribution of lines (from Ramsay, 1967). In either Equal Angleor Equal Area projections, both the axis and the small circle itself are plotted. The"Data Entry" window lists the trend and plunge of the cone axis and the half apical

angle of the cone. A half apical angle of 90 means the cone is equivalent to a cylin-der. A minimum of three lines is needed. The conical best fit algorithm assumes thatall the lines entered are vectors. This can lead to unexpected results, so Stereonetactually does a grid search, progressively rotating the lines and calculating the bestfit cone repeatedly until it finds the best fit of all.

Plot Mean VectorPlots position of mean vector as a solid box on the stereonet. The95% confidence cone will be plotted as a small circle. The color and point symbolused to plot the mean vector is specified in the Symbols Menu. If you ask Stereonetto calculate or plot mean vectors, it will also check the lines array for negativeplunges. If it finds any, you will see a dialog box (below), which asks you how tocalculate and display the mean vector. You can calculate just one mean vector for

the entire data set (No, all together) or you can calculate two, one for upper and onefor lower hemispheres. In the latter case, the statistics are calculated and displayedseparately. The resulting mean vectors and confidence cones can be plotted in eitherthe upper or lower hemisphere. Plotting the mean vector for upper hemispherelines in the lower hemisphere is like performing a reversal test in paleomagneticstudies.


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Equal Area

The Symbols Menu

The Symbols Menu gives you control over the appearance of your plot. You must

select these options before choosing the plot from the Plot Menu. Whatever choices you

make from the Symbols Menu will remain in effect until you select something else from

the menu; it does not automatically revert to the defaults after plotting. Although both

Stereonet and StereoWinhave a Symbols Menu, the organization of the two is quite dif-

ferent. Most notably, in StereoWin, you select shapes, sizes, and colors all in a single

dialog box, whereas in Stereonet, colors are selected from a different submenu than theshapes (because Stereonet uses the Macintosh color picker dialog).

Set SymbolsFrom this submenu, you define the shape, size, and fill for all of the dif-ferent points and great circles that Stereonet can plot (see figure, below left). De-pending on which specific graphic element you choose, the format of the dialogvaries slightly.The graphic element you choose retains its characteristics until youchange it in this menu. You can set your preferred shapes and sizes as the defaultsupon opening the program by choosing Save Preferences in the Edit Menu.

a single data set with negative and positive

plunges plotted separately, and with their cor-

responding mean vectors (in blue) also plotted

se aratel in u er and lower hemis heres


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Set ColorsYou use this submenu (shown above at right) to set the colors for all thegraphic elements in Stereonet, including the background grid. The colors are chosenwith the standard Mac color picker dialog, shown below. You can use any of thecolor schemes at the left side of the dialog.

Set Point/Line AttributesIn StereoWin, you set the size, shape, fill, and color all inthe same dialog box. Both the size and the shape are chosen using the drop downlists, as shown below. When selecting a color, note that you have to click on the ra-dio button to the left of the color and not click on the color itself (which will donothing).

The Set Symbols submenu (below) and the

Set Colors submenu (right) are where you

define the appearance of the various graphicalelements plotted by Stereonet.


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Set Great Circle ColorThis command shows a dialog where one can set the color orthe great circles.

Set MiscellaneousIn this dialog, you set the color, shape, size, and fill for all of theremaining graphic elements in StereoWin, as shown in the figure, below:

Contour ParametersThis choice brings up a dialog box that allows you to change allof the basic aspects of a contour plot. A brief description of each choice in the dialogbox follows:

Set Contour Interval: The default value for the contour interval is 2s (i.e. 2 standarddeviations) or 2% per 1% area. This value can be change to whatever the userwishes; whole numbers or decimals are permitted.

Set Significance Level: This choice allows you to change the default, 3s level for KambContouring. The practical effect is to make the counting circle bigger or smaller de-pending on whether you use a bigger or smaller significance level.


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Contour Patterns Check box:

Shades, Stripes: These are the two different pattern options for the contour plot (asshown in Figure 12); Shades is the default.

Solid Colors, Shaded Colors: Contouring in color is possible on a Macintosh IIequipped with a color screen, if you have selected PICT contours. Shaded colors arethe same as solid except that they are plotted with a 75% gray screen so that theycome out lighter.Contour Patterns are not available in StereoWin.

Terzaghi Correction:

Data that you sample along a 1-D linear transect (borehole, etc.) can be biased by thefact that you are very unlikely to sample a representative number of structures thattrend sub-parallel or parallel to your sampling line. As Randy Marrett explained itto me, to apply the Terzaghi correction for this bias, you just multiply the value ateach counting node times 1/cos(angle between the sample line and the countingnode). The trend and plunge that you enter in the following dialog box gives the ori-entation of the sampling line or transect. Counting nodes that are parallel to thesample line should have a value of infinity, but that would result in an awful lot ofcontours, so you must specify some upper maximum value, the default value being

10.Show NumberIf you select this option, Stereonet will write a number next to each

point in a scatter plot which corresponds to the position of that line in the data file.

Label RecordYou can personalize the Plot Record by selecting "Labels" from the"Symbols" menu. If selected, each time you plot something new a dialog box willappear asking you to label the item. Stereonet starts up with labels not selected.

The contour parameters dialogs differ considerably

between Mac and Windows version. Patterns and

Terzaghi correct are currently unavailable in Win-

dows. Contour colors are chosen separately withthe Set Colors submenu in the Mac version


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Fonts etcThis allows you to determine what font Stereonet uses for the Plot windows.You can only choose the fonts and styles shown in Figure 26 but any size may beentered. These settings apply to everything plotted in the Plot window. It is espe-cially useful when combined with the Annotate Plot menu option described next.

Annotate PlotThis allows you make annotations directly on the plot window that willbe saved with the plot as a PICT file. Annotations can be only one line long and 256characters in length. When you select Annotate plot, the Data Entry Window re-minds you to click the pointer (mouse) at the place where you want the text to occur.The letters will appear immediately to the right and above the pointer tip. To termi-nate an annotation, press the Return Key. Annotations have whatever text charac-teristics you have defined in the Fonts etc. dialog box above.

The Windows Menu

The items in the Windows Menu control the display of the three windows used

by Stereonet. They do nothing more than making a window visible (if it has been hid-

den with the "go-away" box) and they bring the window to the front.

PlotSelect this to show and/or bring to the front the Plot Window. The Plot Windowcan be cleared by selecting "Clear" from the Edit Menu. Either one of these com-mands will erase whatever is in the Plot Record Window as well.

Plot RecordSelect this to show and/or bring to the front the Plot Record Window.StereoWin combines the Plot and Plot Record in a single window.

Data ListSelect this to show and/or bring to the front the Data Entry Window. Thedata list Window does not have a scroll bar, but you can click and drag the mouse inthe window to move through the entire contents.


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Notes on Contouring with Stereonet

Several people have requested more information about how Stereonet does its

contouring. The program uses a rectangular, 21 by 21 grid. The location of each of

these grid points on the sphere is calculated (i.e. the orientation of a reference line to

each grid point, in direction cosines, is calculated). The counting area is actually a

spherical cap on the surface of the sphere (see the following Figure). Once the size of

the counting area is calculated, the apical angle of the cap (a, below) is determined. For

each line in the data set, the angle between it and the vector to the grid point is calcu-

lated. If the angle is smaller than the apical angle of the cap (e.g. for line a, below, y < a)

the line is counted at that grid point; otherwise (e.g. line b) it is not counted. This proc-

ess is repeated for each grid point (for 100 lines: 44,100 calculations). You can see the

number of lines counted at each grid point by holding down the Shift Key while select-ing either Kamb or 1% area contouring. The contours are then painted as a single bit

map (or with many small rectangles if PICT is selected) using a simple algorithm that

interpolates between grid points with 3-pixel resolution (nearly 10,000 more calcula-

tions). Note that, because counting is done on the sphere, you can do contouring in ei-

ther Equal Area or Equal Angle modes. However, the rectangular grid is more dis-

torted and unevenly spaced when projected using an Equal Angle projection (i.e. the

grid points will be squeezed in the middle of the projection and stretched at the edges).

Because the contouring subroutine uses a square grid in which only 20 out of 441

nodes fall on the primitive, there remain slight contour mismatches from one side of the

primitive circle to the other.

Acknowledgment and Referencing

There is no scientific publication that, at present, documents all of the features

contained in Stereonet. Most, if not all, of the scientific algorithms are well known and

documented in various places, such that I have not felt it necessary to clutter the litera-

ture with yet another description of the same routines. Stereonet-produced diagrams

have appeared in several publications, occasionally without identification. The lack of

acknowledgment is understandable; in as much as Stereonet is primarily a plotting pro-

gram, people may not feel any greater obligation to acknowledge it than they do their

favorite spreadsheet or graphics package. On the other hand, one should, maybe, feel


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some obligation to thank or acknowledge a colleague for the use of a program which

they obtained free of charge, if it has saved them a considerable amount of time. It is, I

think, a contribution on the same level as a constructive review of a manuscript or

pointing out the location of a particularly important outcrop. I consider a brief mention

of the use of the program in the Acknowledgments of a paper to be appropriate. (After

all, we all like to know that what we do is useful to others).

Distribution Policy

Stereonet is copyrighte

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