what is a topographic map

8/13/2019 What is a Topographic Map

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What is a Topographic Map . . .What is a Map?

A map is a way of representing on a two-dimensional surface, (a paper, acomputer monitor, etc.) any real-world location or object. Many maps onlydeal with the two-dimensional location of an object without taing into

account its ele!ation. Topographic maps on the other hand do deal withthe third dimension by using contour lines to show ele!ation change onthe surface of the earth, (or below the surface of the ocean).

The concept of a topographic map is, on the surface, fairly simple. "ontour linesplaced on the map represent lines of e#ual ele!ation abo!e (or below) areference datum. To !isuali$e what a contour line represents, picture a mountain(or any other topographic feature) and imagine slicing through it with a perfectlyflat, hori$ontal piece of glass. The intersection of the mountain with the glass is aline of constant ele!ation on the surface of the mountain and could be put on amap as a contour line for the ele!ation of the slice abo!e a reference datum.

The title of the #uadrangle is printed in the upper and lower right corners of themap. %n addition to the title of the #uadrangle itself, the titles of adjacent#uadrangles are printed around the edges and at the corners of the map. Thisallows you to easily find a neighboring map if you areinterested in an area not shown on your map. %n additionthere is information about the projection and grid(s) used,scale, contour inter!als, magnetic and declination.

The legend and margins of topographic #uadranglescontain a myriad of other useful information. Township and

range designations, &TM coordinates, and minute andsecond subdi!isions are printed along the margins of themap. 'ection numbers (from the * system) appear aslarge numbers within a grid of lines spaced one mileapart. The legend also contains a road classification chartshowing different types of roads (pa!ed, gra!el, dirt, etc.).

erhaps one of the most important sources of informationon a topographic map is the date of re!ision, printed to theleft of the scale. Although large scale topographic features (such as mountains)tae millions of years to be formed and eroded, smaller scale features change on

a much more rapid scale. The course of a ri!er channel may change fairly rapidlyas a result of flooding, landslides may alter topography significantly, roads areadded or go out of use, etc. +ecause of these changes, it is important to ha!e afairly recent (or recently updated) topographic map to ensure accuracy. n mosttopographic maps, the date of the initial publication will be shown, along with themost recent re!ision of the map.
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There are many other features (buildings, swamps, mines, etc.) that aredesignated on topographic maps, but which are not described in the map legend.

eference atum. . .

A reference datum is a nown and constant surface which can be used todescribe the location of unnown points. n /arth, the normal reference datum issea le!el. n other planets, such as the Moon or Mars, the datum is the a!erageradius of the planet.

The term 0reference datum0 was used rather than 1abo!e (or below) the earth2ssurface2 or 1abo!e (or below) sea le!el2. The reason for this is simple once youthin about it3%f you use the term 1abo!e the earth2s surface2, what e4actly doesthat mean5 %n other words, the earth2s surface where5

imilarly, although we tend to thin ofsea le!el as a constant, it is not the same e!erywhere on the globe, so sea le!elwhere5 and sea le!el when5 (high tide or low) become pertinent #uestions. o,to a!oid these problems, a reference datum is needed that represents the samesurface or ele!ation at all points on the earth and that remains constant o!ertime. An e4ample of a datum that could be used for the earth is a sphere with aradius e#ual to the a!erage radius of the earth.

uch a sphere would pro!ide a constantsurface to which ele!ations on the earth6sactual surface could be referenced.7owe!er, the earth is not a perfect sphere8the radius of the earth is greater at thee#uator and less at the poles. Theresulting shape is what is nown as an6oblate ellipsoid6. +y using an oblateellipsoid as a datum for the earth we ha!ea shape that appro4imates the shape ofthe earth fairly well and pro!ides a datumto which points all o!er the earth6s surfacecan be referenced (hence the term6reference datum6).

Most 9.: minute topographic maps still in circulation use the ;A-


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(eographic eferencing ystem, =>?B).

More recent maps commonly use the ;A-?C referencing system which is basedon the -?B ellipsoid. The datum used for a map is printed on the front of a

map. Although the reference ellipsoids used in the ;A-


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%ntroduction E Materials . . .

Maps that deal with the surface changes on the earth are called topographicmaps. This e4ercise will loo at how topographic maps are created, whatinformation they contain, how you can use them with a compass to get where you

want to go, and how to measure the relati!e positions of points of interest.

Much of the information discussed is applicable to all types of maps, but for thee4ercises associated with this tutorial, the emphasis will be on informationcontained in a 9.: minute topographic map.

Required Materials:

9.: minute series &.. eological ur!ey topographic #uadrangle

map (=F


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Tips for uderstadi! cotour lies"When first looing at a topographic map, it may appear somewhat confusing andnot !ery useful. There are a few rules that topographic contours must obey,howe!er, and once you understand these rules the map becomes an e4tremelyuseful and easy to use tool.

The rules are as follows:#$/!ery point on a contour line represents the e4act same ele!ation (rememberthe glass inserted into the mountain). As a result of this e!ery contour line muste!entually close on itself to form an irregular circle (in other words, the linecreated by the intersection of the glass with the mountain cannot simplydisappear on the bacside of the mountain). "ontour lines on the edge of a mapdo not appear to close on themsel!es because they run into the edge of the map,but if you got the adjacent map you would find that, e!entually, the contour willclose on itself.

%$"ontour lines can ne!er cross one another. /achline represents a separate ele!ation, and you can2tha!e two different ele!ations at the same point. Theonly e4ception to this rule is if you ha!e ano!erhanging cliff or ca!e where, if you drilled a holestraight down from the upper surface, you wouldintersect the earth2s surface at two ele!ations at thesame I,H coordinate. %n this relati!ely rare case, thecontour line representing the lower ele!ation isdashed. The only time two contour lines may mergeis if there is a !ertical cliff (see figure).

&$Mo!ing from one contour line to another alwaysindicates a change in ele!ation. To determine if it isa positi!e (uphill) or negati!e (downhill) change youmust loo at the inde4 contours on either side (seefigure).

'$n a hill with a consistent slope, there are alwaysfour intermediate contours for e!ery inde4 contour. %fthere are more than four inde4 contours it meansthat there has been a change of slope and one or

more contour line has been duplicated. This is mostcommon when going o!er the top of a hill or acrossa !alley (see figure).

($The closer contour lines are to one another, thesteeper the slope is in the real world. %f the contourlines are e!enly spaced it is a constant slope, if theyare not e!enly spaced the slope changes.

"lic on image for a larger image.

)$A series of closedcontours (the contours maea circle) represents a hill. %fthe closed contours arehatchured it indicates aclosed depression (seefigure).

*$"ontour lines crossing astream !alley will form a 0J0shape pointing in the uphill(and upstream) direction.
http://geology.isu.edu/geostac/Field_Exercise/topomaps/images/topo2.gifhttp://geology.isu.edu/geostac/Field_Exercise/topomaps/images/topo2.gifhttp://geology.isu.edu/geostac/Field_Exercise/topomaps/images/topo2.gifhttp://geology.isu.edu/geostac/Field_Exercise/topomaps/images/topo2.gifhttp://geology.isu.edu/geostac/Field_Exercise/topomaps/images/topo2.gif


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Map cale. . .

i!idual topographic maps are commonly referred to as #uadrangles (or #uads), with the name of theadrangle gi!ing an idea of the amount of area co!ered by the map. The largest area co!ered by mostographic maps used for scientific mapping purposes (i.e. geologic mapping, habitat studies, etc.) are twogrees of longitude by one degree of latitude (see below).

A map of this si$e isreferred to as a 1twodegree sheet2. ne, twdegree sheet can bedi!ided into four small#uadrangles, eachco!ering one degree o

longitude and =K< degof latitude (1one degresheet2).

/ach one degree sheesubdi!ided into eight1fifteen minute#uadrangles2, measurfifteen minutes of latituand longitude.

nally, the smallest topographic #uadrangle commonly published by the &.. geological sur!ey are 9.: minadrangles, which measure 9.: minutes of latitude and longitude. There are four 9.: minute #uads per fiftnute #uad, C< per one degree sheet, and =


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s alluded to abo!e, topographic (and other maps as well) come at a !ariety of scales. The scale of the matermined by the amount of real-world area co!ered by the map. Dor e4ample, 9.: minute topographicadrangles put out by the &.. eological ur!ey ha!e a scale of =F


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7ow far your path !ariedfrom true north dependson where you startedfrom8 the angle betweena straight north-south

line and the line youwaled is the magneticdeclination in the areayou were waling.

%n the e4ample below, ifyou waled =.


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The scales discussed before only deal with therelationship between hori$ontal distances on the mapand hori$ontal distances in the real world. +ecausetopographic maps incorporate the third (!ertical)dimension of the earth2s surface, they also ha!e a

!ertical scale.

This scale is listed on a topographic map as the contour inter!al. The contourinter!al is the !ertical distance represented by consecuti!e contour lines on themap. %n general, the smaller the scale of the map (remember, small scale mapsshow a larger area of the earth2s surface) the larger the contour inter!al will be.Dor e4ample, the contour inter!al on a 9.: minute #uad is commonly GB feet,while on a one or two degree sheet it will often be =BB feet. %n order to maetopographic maps more useful, there are e4ceptions to this rule of thumb.

%n !ery flat areas, such as the plains of the midwest or the nae i!er lain,

contour inter!als of one hundred, or e!en forty, feet may not be !ery useful asthey will be !ery widely spaced. %n areas such as these, supplemental contoursare often added at fi!e or ten foot inter!als (supplemental contours appear on& topographic maps as dashed lines). imilarly, in !ery steep mountainousareas the contours may be more widely spaced to a!oid clustering of lines intounreadable masses. The contour inter!al used on a topographic map is printedbelow the scale in the map legend.

egardless of the contour inter!al chosen, you will notice that there are at leasttwo types of contour lines on a topographic map. Thic contour lines, calledinde4 contours, ha!e ele!ations printed on them periodically o!er their length.

+etween each inde4 contour are four intermediate contours that are thinner linesthan the inde4 contours. The ele!ation change between the intermediatecontours is what is gi!en in the map legend. o, if the contour inter!al listed inthe map legend is forty feet, each intermediate contour represents forty feet andthe ele!ation change between inde4 contours is


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"reating Topographic rofiles . . .

ery useful e4ercise for understanding what topographic maps represent is the construction of a topograpfile. A topographic profile is a cross-sectional !iew along a line drawn through a portion of a topographicp. %n other words, if you could slice through a portion of the earth, pull away one half, and loo at it from e, the surface would be a topographic profile. ;ot only does constructing a topographic profile aid inderstanding topographic maps, it is !ery useful for geologists when analy$ing numerous problems.

construct a topographic profile, you must first decide on a line that is of interest to you. This could be anere you want to go for a hie and want to now how steep to e4pect it to be, a line that shows the ma4imuef (relief is the difference in ele!ation between the highest and lowest points) in the map area, or any othea in which you are interested. nce you ha!e determined where you want to draw your profile, use theowing guidelines to construct your profile.

encil the line of your interest in lightly on your map, or you can putlar o!er the map and draw on it if you don6t wish to mar your map.you use mylar- it may be a !ood idea to mar. the corers of the map o thear so you ca reoriet the mylar o the map later if ecessary"++

lace a blan piece of paper along the line you ha!e drawn. Hou maynt to tape the paper to the map using drafting tape to eep them from!ing relati!e to one another (don2t use any other ind of tape unless

u don2t mind taing some of the map off with the tape later).

n both the blan paper and the map (or mylar), mar clearly therting and ending points of your line of section. +elow these mars,te down the ele!ation of the starting and ending points of your

ction"

Mae a tic mar where!er the paper crosses a contour line on the map, maing larger tics for the inde4ntours and smaller tics for the intermediate contours. Write the ele!ation of the inde4 contours below theyour paper3you might want to start off writing the ele!ation of the intermediate contours as well to a!oid

nfusion, but it will soon become tedious.

e a note of the highest and lowest points on the profile for use later. +e sure to eep trac of the numb

ermediate contours between the major contours8 if there are more than four intermediate contours it meant there has been a change in slope and you need to chec to see if you crossed a hill or a !alley.

nce you are certain you ha!e all of the appropriate tic mars and ele!ations, remo!e your paper from thp. et a piece of graph paper that is at least as long as your line of section (you can piece them togethe

u ha!e to, but mae sure all the grids line up). %f you are using a map with a scale of =F


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raw !ertical lines abo!e your starting and ending points, these will be the boundaries of your profile. &s4imum and minimum ele!ations along your line of section to determine how long to draw these lines. Do

ample, if your minimum ele!ation is GC


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epending on why you are creating your topographic profile, you may want touse !ertical e4aggeration when constructing it.

Jertical e4aggeration simply means that your !ertical scale is larger than yourhori$ontal scale (in the e4ample you could use one inch is e#ual to =BBB ft. for

your !ertical scale, while eeping the hori$ontal scale the same). Jerticale4aggeration is often used if you want to discern subtle topographic features or ifthe profile co!ers a large hori$ontal distance (miles) relati!e to the relief (feet).

To determine the amount of !ertical e4aggeration used to construct a profile,simply di!ide the real-world units on the hori$ontal a4is by the real-world units onthe !ertical a4is.

%f the !ertical scale is one =0O=BBB2 and the hori$ontal scale is =0O


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"alculating a lope . . .

etermining the a!erage slope of a hill using a topographic map is fairly simple.lope can be gi!en in two different ways, a percent gradient and an angle of theslope. The initial steps to calculating slope either way are the same.

#$ecide on an area for which you want to calculate the slope (note, it should bean area where the slope direction does not change8 do not cross the top of a hillor the bottom of a !alley).

%$nce you ha!e decided on an area of interest, draw a straight lineperpendicular to the contours on the slope. Dor the most accuracy, start and endyour line on, rather than between, contours on the map.

&$Measure the length of the line you drew and, using the scale of the map,con!ert that distance to feet. (insert image with the line drawn on it, con!ersioncalculation)

'$etermine the total ele!ation change along the line you drew (subtract theele!ation of the lowest contour used from the ele!ation of the highest contourused). Hou do not need to do any con!ersions on this measurement, as it is areal-world ele!ation change.

To calculate a percent slope, simply di!ide the ele!ation change in feet by thedistance of the line you drew (after con!erting it to feet). Multiply the resultingnumber by =BB to get a percentage !alue e#ual to the percent slope of the hill. %fthe !alue you calculate is, for e4ample,


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. &sing a "ompass with a Map . . .ictured below are two different types of compasses. The compass at left is a

+runton compass used by geologists and others for many speciali$ed mappingpurposes. n the right is a more common type of compass used for generalorienteering and some mapping purposes. The features of a compass that youneed to understand are found on both types of compass (and most others aswell). This section will gi!e an o!er!iew of how to use a compass with atopographic map to locate yourself on the map and how to get from one point inthe map area to another.
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et a +earing. . .bearing is a measurement of direction between two points. +earingse generally gi!en in one of two formats, an a$imuth bearing or aadrant bearing.

a$imuth bearing uses all C@B of a compass to indicate direction.e compass is numbered clocwise with north as B, east >B, southB, and west


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Dinding elf on a Map . . .w you now how to get from point A to point + on ap using your compass3but what if you are not sureere e4actly point A is (i.e. you are lost)5 +y far thesiest way to determine where you are on a map is to

l out your pocet (global positioning systemcei!er) and ha!e it gi!e you your map coordinates. %f,we!er, you are lie a lot of people, you don2t want toell out a few hundred bucs for a and, unlessu are in an area with !ery little topographic relief, youn2t need one. Hou can determine your position #uitecurately on a topographic map by using yourmpass to triangulate between three points.

The first step in triangulation is to pic threetopographic features that you can see and

can identify on your map (mountains areideal). tart with the first feature you ha!echosen and determine the bearing betweenyou and it, as outlined abo!e. nce you ha!edetermined its bearing, pencil in a line withthe same bearing on your map that runsthrough the chosen feature (once again,ha!ing a protractor would be useful). epeat

this for the other two features, drawing lines for each. The point where the threelines intersect on the map is where you are. epending on how accurate yoursightings were and how accurately you drew your lines through the features,

there will probably be a some error in your location. +e sure to double chec themap and reconcile it with what you see. %f the lines intersect in a !alley and youare on a hill, the location is ob!iously off a bit on the map. %t does gi!e a goodappro4imation though and, by looing at your surroundings, you should be ableto figure out which hill on which side of the !alley you are on. %f you ha!e analtimeter with you, you can also use it with the triangulation to help determineyour e4act location more accurately.


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/4ercise ne . . .

0urpose:+ecome familiar with all of the parts of your map and the informationcontained in your map.

Dor this e4ercise, if you ha!e not done so already, obtain a =F


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COOR&I%AT" S'ST"MS

Two types of coordinate systems are found on most topographic maps:

latitude(longitude

towns#ip(range

The latitude-longitude system is universally used throughout the world. The township-

range system is only used in western and southern states.

!ATIT)&"(!O%GIT)&"

The Earth's surface is divided by an imaginery coordinate grid. This grid is defined bytwo %inds of lines:

latitude(or parallels): run east-west

longitude(or meridians): run north-south

The location of any point on the Earth's surface can be indicated by the numbers(coordinates) of the line of latitude and line of longitude that cross it.

The coordinate numbers of latitude and longitude are angular measurements:

coordinate of any line of latitude: angle between line and e&uator coordinate of any line of longitude: angle between line and prime meridian


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The coordinate angles are measured in units of degrees, minutes, and seconds: # degree () $ minutes (')

# minute (') $ seconds (")

Topo maps usually come in two si*es:

*+,- .uadrangle: which e!tend +.' (#) of latitude from north and south and

+.' of longitude from east to west

/,- .uadrangle: which e!tend #' (#/) from north to south and from east to

west

MAP S'M$O!S

Topographic maps use a variety of symbols to show the location of physiographic andcultural features, the type and density of vegetation, and the elevation of the land.

The standard symbols (established by the 0nited 1tates 2eological 1urvey) are shown in

Table -#.

CO%TO)R !I%"S

Topographic maps are distinctive from other maps in the use of contour lines to showthe elevation, relief and slope of the land.

elevation: vertical distance from sea level

relief: difference in elevation between two points slope: change in elevation over a given hori*ontal distance

Contour lines: imaginary lines connecting points of e&ual elevation.

Contour interval: difference in elevation between two ad3acent contour lines:

usually constant on any given map

every contour line is a multiple of

the contour interval


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Inde0 contour: every fifth contour line is printed thic%er, and then mar%ed with its

elevation for reference.

R"A&I%G CO%TO)R !I%"S1

#. Every fifth line in a series of contours in an inde! contour (see point on 4igure -+)5. The elevations of specific points are noted by benc#mar2s(see points 6 and 7)

8. The elevation of any point on a contour line is e&ual to the elevation of that contour

line:9hat is the elevation of point ;

/. The elevation of any point that lies between two contour lines is estimated on the basis

of its relative distances from these lines.9hat is the elevation of point E;

. The spacing of contour lines is proportional to the slope of the land.

1lope7ontour

evel ground ?o contours 4

0niform slope E&ually spaced contours 2

2entle slope 9idely spaced contours @

1teep slope 7losely spaced contours A

Bertical cliff Cerged contours -

. Every point enclosed by a solidcontour line is topographically higher than the line

itself. 1olid contour lines enclose topograp#ic #ig#s(see point D).

+. 7ontour lines which cross rivers and valleys form Bs that point in the upstreamdirection (point >).

. @achured lines are used to mar% the contours of closed depressions with no outlets

such as ponds (see point )

F. Every point enclosed by a hachured contour line is topographically lower than thatline.

#$. The outer hachured contour line around a topographic low has the same elevation as

the closest solid contour line.

TOPOGRAPHIC PRO3I!"S

Topographic maps provide a plan view of the shape of the Earth's surface.


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different perspective on the shape of the Earth's surface is the cross-section view,

called a topograp#ic proile.

The creation of a topographic profile is shown in 4igure -.

4"RTICA! "5AGG"RATIO%

4ertical e0aggeration (BE): the distortion of the vertical scale of a topographic profile

to emphasi*e the relief and slope of the land.

BE vertical scale divided by hori*ontal scale4or e!ample, the vertical scale in 4igure -c is #"#$$'G the hori*ontal scale is #"#$$$'.

ST"R"OPHOTOGRAPHS

To use stereophotographs:#. >ocate a prominent point or feature that is present in both images.

5. Hlace center of stereoscope directly over the line separating the two images, and ad3ust

the lenses so that they are directly over the same point in each image.8. >oo% through stereoscope and rela! your eyes. The images will merge. Af they do not,

twist the stereoscope until they do.

6ac% to the Hhysical 2eology >ab @omepage

6ac% to E17A ##5 >ab >ist

?ame

ate

Topograp#ic Maps !ab

Introduction

Cost atlas maps are too "small-scaled" to show the details of landforms. The

generali*ations of gross landform regions (mountains, hills, plateaus and plains) oftenobscure as much about a region as they tell us. Ine must turn to large-scale maps when it

is necessary to show more precisely the local variations in slope and elevation. An the

0nited 1tates we depend heavily upon the detailed topographic maps prepared by the0nited 1tates 2eological 1urvey (0121).
http://geoweb.tamu.edu/courses/geol101/labhttp://www.homepage.montana.edu/~escicrs/esci112/_fall_labs/fall_labs.htmhttp://geoweb.tamu.edu/courses/geol101/labhttp://www.homepage.montana.edu/~escicrs/esci112/_fall_labs/fall_labs.htm


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The contour lines on 0121 topographic maps follow a set of loosely defined "rules"

which you should learn and understand. 1everal of the most basic rules that will be used

in this e!ercise are listed below:

Hoints lying between contour lines must be interpolated to find their elevation.

4or e!ample, a point lying midway between contours ,//$ and ,/$ would be,/$' above sea level.

7ontour lines never intersect or cross one another, although in special cases they

may be shown to be superimposed.

7ontour lines curve in an upstream direction when they cross a stream valley.

Every contour line should eventually meet itself, either inside or outside the

map area.

9here contours are spaced close together, the topography is steepG where they

are far apart the slopes are gentler.

An addition to contour lines and their elevations, the heights of many identifiable points,such as road intersections, mountain summits, and surfaces of la%es are shown on the

map in printed figures, giving the elevation to the nearest foot. These individual

elevations are commonly referred to as spot elevations.

The map scale limits the amount of information that can be shown on a map. 0121 mapsare intended to give as complete a picture of the terrain as can be legibly reproduced at

publication scale. Cany relatively unimportant features are omitted and many small but

important features are necessarily e!aggerated in si*e to ma%e them more readable. 1omefeatures are mapped because of their relative importance on a regional basis, such aswells and springs in the arid western states.

The landscape and accompanying topographic map reproduced in 4igure # should assist

in your understanding of these important rules.


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3igure /

Public !and Survey

System

An addition to latitude and

longitude, there are several

other ways to describe the

location of points on atopographic map. system

in use in the 0nited 1tates is

the 01 Hublic >and 1urvey1ystem (H>11). This system

was devised by Thomas

Defferson and employsroughly s&uare tracts of

different si*es. The smallest

and most fundamental of these s&uare parcels of land is called asection, a s&uare, one

mile on a side, containing /$ acres. These mile s&uares may be subdivided into fourmore s&uares called quarter sections, and these may be further subdivided as shown in

4igure 5. 1ections are grouped into large s&uare parcels of land called townships, each

township si! miles on a side and containing 8 sections. ?umbering of sections in eachtownship begins with the northeast corner section, and proceeds west to section , then to

the south to ad3acent section +, and bac% to the east along the second tier of sections to

section #5. This *ig*ag pattern continues until all 8 sections are numbered (4igure 5)

Townships are also organi*ed into a grid system, being arranged along a north-southprincipal meridianand along an east-west baseline. Townships are arrayed both north

and south of the baseline and are numbered accordingly, being given township numbersbased on a given townshipKs relative pro!imity to the baseline. Townships are also

arrayed along east-west lines. @ere, they are located by range numbers, depending on the

position of the township east or west of the principle meridian.


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/+ Map Interpretation

Ob6ective7 To e!plore the components of a topographic map, and use some analytical

techni&ues.

Materials %eeded70121 Cap of Ciner, CT, 7alculator,


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5. 9hat is the map scale; @ow many feet on the ground does one inch on the map

represent;

8. 9hat is the map pro3ection;

/. 9hat is the contour interval; 9hat is the interval between inde! contours;

. 9hich map would you need to obtain in order to see the terrain upstream of

Lan%ee Dim 7anyon on the Lellowstone atitude>ongitude to the nearest minute. 2ive the summit location in

H>11 grid (&uarter section, section, township, range).

+. 4ind 9igwam 7ree%. 9hich direction (upstream or downstream) do the "B's"

in the contour lines point;

. @ow many feet does Tom Ciner 7ree% descend from the western edge of the

map to its confluence with the Lellowstone ocate "og Tooth


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#$. >oo% at the south slope of og Tooth


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. >abel all distinguishing features on the profile (pea%s, rivers, la%es,

cities, etc.)

. etermine the scale of the vertical a!is (inches on the graph per feet onthe ground).

+. ivide the hori*ontal a!is scale by the vertical a!is scale to get the

vertical e!aggeration.

. 7reate a legend with the following information:

?ame of Hrofile (Endpoints and compass direction)

?ame of Cap

@ori*ontal 1cale (7opy a graphic scale from the map)

Bertical E!aggeration

Part II7 Create a second proile t#e same as t#e irst one= but wit# #al t#e

vertical e0aggeration+ 'ou may eit#er use t#e bac2 o t#e grap# paper= or

create a second vertical a0is on t#e rig#t side o your original proile= and use

t#e same #ori>ontal a0is :be sure to ma2e it clear w#ic# proile goes wit#

w#ic# a0is?;+

#. 7ompare the two profiles. 9hich profile provides a more accurate

representation of the landscape;

@+ Ma2ing a Topograp#ic Map

Ob6ective70sing survey points to create a topographic map.

Materials %eeded7Hencil, Cap of 1urvey Hoints.

Procedure7

#. 0se the diagram of survey points below to create a contour map with a /(

meter contour interval+ %OT"7 T#e BRim o CraterB is %OT a contour line?

5. An the space below, s%etch a profile of your new map from point Ato point A.


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Topographic Caps

Introduction

topographic mapis a detailed and accurate two-dimensional representation of

natural and human-made features on the Earth's surface. These maps are used

for a number of applications, from camping, hunting, fishing, and hi%ing to

urban planning, resource management, and surveying. The most distinctive

characteristic of a topographic map is that the three-dimensional shape of the

Earth's surface is modeled by the use of contour lines. 7ontours are imaginary

lines that connect locations of similar elevation. 7ontours ma%e it possible to

represent the height of mountains and steepness of slopes on a two-dimensional

map surface. Topographic maps also use a variety of symbols to describe both

natural and human made features such as roads, buildings, &uarries, la%es,

streams, and vegetation

Contour !ines

Topographic mapscan describe vertical information through the use of contour

lines(contours). contour line is an isolinethat connects points on a map that

have the same elevation. 7ontours are often drawn on a map at a uniform

vertical distance. This distance is called the contour interval. The map in the

3igure 8d(/shows contour lines with an interval of #$$ feet. ?ote that every

fifth brown contour lines is drawn bold and has the appropriate elevation

labeled on it. These contours are called inde! contours. In 3igure 8d(/they

represent elevations of $$, #$$$, #$$, 5$$$ feet and so on. The interval at

which contours are drawn on a map depends on the amount of the relief

depicted and the scale of the map.
http://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/t.html#anchor301225http://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/i.html#isolinehttp://www.physicalgeography.net/physgeoglos/c.html#contour_intervalhttp://www.physicalgeography.net/physgeoglos/i.html#index_contourhttp://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/t.html#anchor301225http://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/c.html#contourhttp://www.physicalgeography.net/physgeoglos/i.html#isolinehttp://www.physicalgeography.net/physgeoglos/c.html#contour_intervalhttp://www.physicalgeography.net/physgeoglos/i.html#index_contour


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3igure 8d(/7 Hortion of the "Toino" #:$,$$$ %ational

Topograp#ic Series o Canadamap. The brown lines

drawn on this map are contour lines. Each line represents a

vertical increase in elevation of #$$ feet. The bold brown

contour lines are called inde! contours. The inde! contours

are labeled with their appropriate elevation which increases

at a rate of $$ feet. ?ote the blue line drawn to separate

water from land represents an elevation of $ feet or sea-level.

7ontour lines provide us with a simple effective system for describing

landscape configuration on a two-dimensional map. The arrangement, spacing,

and shape of the contours provide the user of the map with some idea of what

the actual topographic configuration of the land surface loo%s li%e. 7ontour

intervals the are spaced closely together describe a steep slope. 2entle slopes

are indicated by widely spaced contours. 7ontour lines that B upwards indicatethe presence of a river valley.


34/36

topographic profileis a two-dimensional diagram that describes the

landscape in vertical cross-section. Topographic profiles are often created from

the contour information found on topographic maps. The simplest way to

construct a topographic profile is to place a sheet of blan% paper along a

hori*ontal transect of interest. 4rom the map, the elevation of the various

contours is transferred on to the edge of the paper from one end of the transect

to the other. ?ow on a sheet of graph paper use the !-a!is to represent the

hori*ontal distance covered by the transect. The y-a!is is used to represent the

vertical dimension and measures the change in elevation along the transect.

Cost people e!aggerate the measure of elevation on the y-a!is to ma%e changes

in relief stand out. Hlace the beginning of the transect as copied on the piece of

paper at the intersect of the ! and y-a!is on the graph paper. The contour

information on the paper's edge is now copied onto the piece of graph paper.

3igure 8d(8shows a topographic profile drawn from the information found on

the transect A($above.

3igure /d(87 The following topographic profile shows the

vertical change in surface elevation along the transect A$

from 3igure /d(/. vertical e!aggeration of about /.5

times was used in the profile (hori*ontal scale #:$,$$$,

vertical scale #:#5,$$$ and vertical e!aggeration

hori*ontal scalevertical scale).

Military Grid Reerence System and Map !ocation

Two rectangular grid systems are available on topographic maps for identifying

the location of points. These systems are the 0niversal Transverse Cercator

()TM) grid systemand the Cilitary 2rid


35/36

Grid Reerence Systemis a simplified form of )niversal Transverse

Mercator grid systemand it provides a very &uic% and easy method of

referencing a location on a topographic map. In a topographic maps with a

scale #:$,$$$ and larger, the Military Grid Reerence Systemis

superimposed on the surface of map as blue colored series of e&ually spaced

hori*ontal and vertical lines. Adentifying numbers for each of these lines is

found along the map's margin. Each identifying number consists of two digits

which range from a value of $$ to FF (3igure 8d(@). Each individual s&uare in

the grid system represents a distance of a #$$$ by #$$$ meters and the total

si*e of the grid is #$$,$$$ by #$$,$$$ meters.

Ine problem associated with the Military Grid Reerence Systemis the fact

that reference numbers must be repeat every #$$,$$$ meters. To overcome this

difficulty, a method was devised to identify each #$$,$$$ by #$$,$$$ meter

grid with two identifying letters which are printed in blue on the border of all

topographic maps (note some maps may show more than one grid). 9hen

ma%ing reference to a location with the Military Grid Reerence System

identifying letters are always given before the hori*ontal and vertical

coordinate numbers.

3igure 8d(@7 Hortion of a Military Grid Reerence

Systemfound on a topographic map. 7oordinates on this

system are based on a 5(hori*ontal increasing from left toright) and '(vertical increasing from bottom to top)

system. The symbol depicting a church is located in the

s&uare D/DE. ?ote that the value along the 5-a!is (easting)

is given first followed by the value on the '-a!is (northing).

(Source: 7entre for Topographic Anformation, %atural

Resources Canada).
http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://maps.nrcan.gc.ca/http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://maps.nrcan.gc.ca/


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Each individual s&uare in the Military Grid Reerence Systemcan be further

divided into #$$ smaller s&uares (ten by ten). This division allows us to

calculate the location of an ob3ect to within #$$ meters. 3igure /d(E indicates

that the church is si! tenths of the way between lines D/and D8, and four tenths

of the way between lines DEand D,. 0sing these values, we can state that the

eastingas being D/Fand the northingas DEE. 6y convention, these two

numbers are combined into a coordinate reference of D/FDEE.

3igure 8d(E7 4urther determination of the location of the

church described in 3igure 8d(@. 0sing the calibrated ruler

we can now suggest the location of the church to be D/Fon

the 5-a!is and DEEon the '-a!is. ?ote that the location

reference always has an even number of digits, with the

three digits representing the eastingand the second three thenorthing. (Source: 7entre for Topographic Anformation,

%atural Resources Canada).
http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://maps.nrcan.gc.ca/http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://www.physicalgeography.net/physgeoglos/e.html#eastinghttp://www.physicalgeography.net/physgeoglos/n.html#anchor591307http://maps.nrcan.gc.ca/

what is a topographic map

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