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ESRM 304: Environmental and Resource Assessment © Phil Hurvitz, 1999-2009 ESRM 304 Spring 2013 Peter Schiess / Eric Turnblom Introduction to Surveying, Datums & Coordinate Systems

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Page 1: Introduction to Surveying, Datums & Coordinate Systems 304... · Introduction to Surveying, Datums & Coordinate Systems . ... Surveying methods ... Start with one traverse vertex

ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

KEEP THIS TEXT BOX this slide includes some ESRI fonts.

when you save this presentation, use File > Save As > Tools (upper right) > Save Options

> Embed TrueType Fonts (all characters) this will allow vector maps created with

common ESRI symbols to show on computers that do not have ESRI software loaded

a a a a a a a a a a a a

ESRM 304 Spring 2013

Peter Schiess / Eric Turnblom

Introduction to Surveying, Datums & Coordinate Systems

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

  Overview of surveying   What is a map?   How are features placed on a map?   How do we trust things that are on a map?   Datums, land division systems, & coordinate systems

Overview

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

What is surveying?

“The science and art of making all essential measurements to determine the relative position of points and/or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points and/or details.”

-American Congress on Surveying and Mapping (ACSM)

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

Why survey? Surveying allows us to get accurate and valid

measurements of things that are on the surface of the earth.

Why would this be important? What would you

want to measure? [Discussion]

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

History of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

History of surveying (from Wikipedia)   The Egyptian land register (3000 BC).   A recent reassessment of Stonehenge (c.2500 BC) indicates that the

monument was set out by prehistoric surveyors using peg and rope geometry.

  Under the Romans, land surveyors were established as a profession, and they established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD).

  The rise of the Caliphate led to extensive surveying throughout the Arab Empire. Arabic surveyors invented a variety of specialized instruments for surveying, including:   Instruments for accurate leveling: A wooden board with a plumb line and two

hooks, an equilateral triangle with a plumb line and two hooks, and a reed level.   A rotating alhidade, used for accurate alignment.   A surveying astrolabe, used for alignment, measuring angles, triangulation, finding the

width of a river, and the distance between two points separated by an impassable obstruction.

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

History of surveying   In England, The Domesday Book by William the

Conqueror (1086)   covered all England   contained names of the land owners, area, land quality, and specific

information of the area's content and habitants.   did not include maps showing exact locations

  Continental Europe's Cadastre was created in 1808   founded by Napoleon I (Bonaparte)   contained numbers of the parcels of land (or just land), land

usage, names etc., and value of the land   100 million parcels of land, triangle survey, measurable survey, map

scale: 1:2500 and 1:1250   spread fast around Europe, but faced problems especially in

Mediterranean countries, Balkan, and Eastern Europe due to cadastre upkeep costs and troubles.

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

Surveying methods (2 main methods):   Geodetic surveying

  Takes into account the theoretical shape of the earth.   Generally high in accuracy, and covering large areas (greater

than 300 mi2).

  Plane surveying   Assumes that the survey area is a flat plane.   Generally covers small areas (less than 300 mi2).   Most common method used.

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

Types of surveys   Control surveys   Topographic   Land, Boundary and Cadastral surveys

  Original surveys   Retracement surveys   Subdivision surveys

  Hydrographic surveys   Route surveys   Construction surveys   As-built surveys   Mine surveys

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

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Control of the surveying profession and standards

  National Geodetic Survey (NGS)   Bureau Of Land Management (BLM)   The U.S. Geological Survey (USGS)   The Defense Mapping Agency (DMA)   U.S. Army Corps Of Engineers (COE)

Strict licensing   State licensing boards   Apprenticeships

Overview of surveying

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ESRM 304: Environmental and Resource Assessment

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It’s all about triangles: Pythagoras knew, and so should you!

Survey mathematics

c. 570-c. 495 BC

a2 + b2 = c2

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ESRM 304: Environmental and Resource Assessment

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The Law of Sines

Survey mathematics

b a

c

C

B A

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

The Law of Sines:   Given:

  two sides and one angle or   two angles and one side

  It is possible to get values of all angles and all sides

Survey mathematics

Example: given side a = 20, side c = 24, and angle C = 40°

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Measurement devices   Three basic instruments are used, to measure

distance and angles.   Compass for planimetric angle   Clinometer for elevation angle   Tape for distance

  Other devices may be used (e.g., theodolite, laser rangefinder), but the basic functionality is the same

Collecting and recording data

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  Looking from point to point, deviation from north is measured

  May include correction for magnetic declination (true north and magnetic north may vary)

  Mirror allows the user to sight the target and adjust the dial simultaneously

  May need to step away from ferrous metallic objects to avoid magnetic effects

Compass

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Rotating dial indicates angle of elevation   Align the cross hair with the target   Read the angle of inclination through the viewfinder   Percent scale is on the left; degree

on the right   Depending on your

application, record in either degree or percent (use percent for this course)

Clinometer

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ESRM 304: Environmental and Resource Assessment

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Simple device for measuring distance   Various materials are used (for strength, lack of

elasticity, etc.)   Proper tension required to avoid sag   Straight line required

(sometimes vegetation needs to be cut)

  Air temperature should be recorded (due to shrink/expansion)

Measuring tape

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ESRM 304: Environmental and Resource Assessment

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Horizontal distances are assumed   If stations are not at the same elevation, the tape

should be held level.   If this is not possible, measure the elevation angle and

correct using the law of sines

Measuring slope distance

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No measurements are perfect. Various problems can arise from different sources.   Some are systematic, and if known, can be corrected (e.g.,

incorrect tape length, incorrect declination set on compass)   Some are random and cannot be controlled

  Examples   Device limitations (precision limits)   Environment conditions (e.g., expansion/shrinking of tape)   Blunders (user error)   Magnetic anomalies   Others?

Surveying data

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Correcting angular error   Sum of interior angles should be close to

where n = count of angles   Maximum error should be

where k = the smallest division readable on the compass

Correcting surveying data

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ESRM 304: Environmental and Resource Assessment

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Correcting linear measures   First, lengths of sides must be calculated (again, with

trigonometric functions)

Correcting surveying data

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Getting XY coordinates of stations   Start with one traverse vertex with known XY

coordinates   Add latitudes and departures

sequentially

Completing data

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Mapping   XY coordinates can be plotted on a map or entered

into a GIS

Completing data

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

  Overview of Surveying   What is a map?   How are features placed on a map?   How do we trust things that are on a map?   Datums, land division systems, & coordinate systems

Overview

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

What is a map? What is the purpose of a map? How do you know if a map is meeting its

intended purpose (or your purpose)?

What is a map?

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What is a map?

Archaeologists have discovered what they believe is the earliest known map, dating from almost 14,000 years ago. (in Spain)

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ESRM 304: Environmental and Resource Assessment

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What is a map?

A Neo-Babylonian (Persian Period, circa 500 BCE) copy of an original map dating to the Sargonid Period, circa late eighth or seventh century BCE

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What is a map?

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What is a map?

The Waldseemüller map, Universalis Cosmographia, is a wall map of the world drawn by German cartographer Martin Waldseemüller originally published in April 1507. It was one of the first maps to chart latitude and longitude precisely, following the example of Ptolemy, and was the first map to use the name “America.” Waldseemüller also created globe gores, printed maps designed to be cut out and pasted onto spheres to form globes of the Earth.

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What is a map?

The Piri Reis map is a famous pre-modern world map compiled in 1513 from military intelligence by the Ottoman-Turkish admiral and cartographer Piri Reis.

Page 31: Introduction to Surveying, Datums & Coordinate Systems 304... · Introduction to Surveying, Datums & Coordinate Systems . ... Surveying methods ... Start with one traverse vertex

ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

  Overview of Surveying   What is a map?   How are features placed on a map?   How do we trust things that are on a map?   Datums, land division systems, & coordinate systems

Overview

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ESRM 304: Environmental and Resource Assessment

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How did all those maps get made?

How are features placed on a map?

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

  Overview of Surveying   What is a map?   How are features placed on a map?   How do we trust things that are on a map?   Datums, land division systems, & coordinate systems

Overview

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© Phil Hurvitz, 1999-2009

Control is essential Careful measurements taken from known

locations How do we know what a “known location” is? How do you know where you are? [Discussion] Hint: how long is a meter?

How do we trust things that are on a map?

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How do we trust things that are on a map?

Short answer: by agreement (length of a meter)   18th Century: 1/10,000,000 of the length from the Equator to the North Pole (“the

meridian”)   1792-1799: expedition measured the length between Dunkerque and Barcelona (1/2

of the meridian)   1875: Bureau International des Poids et Mesures: the distance between two lines on

a standard bar composed of an alloy of 90% Pt and 10% Ir, measured at the melting point of ice

  1960: 1,650,763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of 86Kr in a vacuum

Agreement requires standards Measurement frameworks are the result of

agreement and standards

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

  Overview of Surveying   What is a map?   How are features placed on a map?   How do we trust things that are on a map?   Datums, land division systems, & coordinate systems

Overview

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Datums (from Wikipedia)   A geodetic datum (plural datums, not data) is a

reference from which measurements are made.   In surveying and geodesy, a datum is a set of

reference points on the earth's surface against which position measurements are made, and

  (often) an associated model of the shape of the earth (reference ellipsoid) to define a geographic coordinate system.

Datums, land division systems, & coordinate systems

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Datums (from Wikipedia)   Horizontal datums are used for describing a point on

the earth's surface, in latitude and longitude or another coordinate system.

  Vertical datums measure elevations or depths. In engineering and drafting, a datum is a reference point, surface, or axis on an object against which measurements are made.

Datums, land division systems, & coordinate systems

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Datums   Is the earth a sphere? No, it is a spheroid/ellipsoid   The earth is irregularly shaped   Deformations in the crust (e.g., from gravitational

pressure of ice)   Gravitational forces different where crust thickness

varies

Datums, land division systems, & coordinate systems

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ESRM 304: Environmental and Resource Assessment

© Phil Hurvitz, 1999-2009

Datums are mathematical models of the shape of the earth created to provide control over the survey measurement framework

Provide a frame of reference for measuring locations on the earth’s surface

Earth-centered datums (e.g., WGS84) provide locational control for the entire planet but do not fit specific locations particularly well

Local datums exist for better local control (e.g., NAD27 or NAD83 for North America)

Datums, land division systems, & coordinate systems

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ESRM 304: Environmental and Resource Assessment

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Datums, land division systems, & coordinate systems

These points represent the same location in two different datums

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Datums, land division systems, & coordinate systems

Coordinate systems and land divisions extend the concept of the datum

Establish a (Cartesian) measurement framework Allow referencing of all features on, above, or

below the surface of the earth to each other

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ESRM 304: Environmental and Resource Assessment

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Datums, land division systems, & coordinate systems

Examples of different referencing systems   Metes and bounds   US Public Land Survey System (PLSS)   State Plane   Universal Transverse Mercator (UTM)

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Metes and bounds

Based on physical features of local geography, directions, and distances

E.g., "beginning with a corner at the intersection of two stone walls near an apple tree on the north side of Muddy Creek road one mile above the junction of Muddy and Indian Creeks, north for 150 rods to the end of the stone wall bordering the road, then northwest along a line to a large standing rock on the corner of John Smith's place, thence west 150 rods to the corner of a barn near a large oak tree, thence south to Muddy Creek road, thence down the side of the creek road to the starting point."

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Metes and bounds

What problems could there be with metes and bounds?

[Discussion]   Irregular shapes for properties lead to complex

descriptions   The only thing constant is change: trees die, streams

move by erosion, properties are sold   Not useful for large, newly surveyed tracts of land

being opened in the west, which were being sold sight unseen to investors

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US Public Land Survey System (PLSS)

Established in 1875 (Land Ordnance Survey) Origin point in E. Ohio

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US Public Land Survey System (PLSS)

Willamette Meridian

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US Public Land Survey System (PLSS)

Townships and ranges are specified in relation to a meridian

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US Public Land Survey System (PLSS)

Townships and ranges are specified in relation to a meridian

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US Public Land Survey System (PLSS)

Townships are subdivided sequentially to refer to specific locations

E.g., “NE ¼ of NW ¼ of section 16 of township 23 N, range 16 E of Willamette Meridian”

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US Public Land Survey System (PLSS)

The legacy persists:   Each 16th section was originally set aside for support

of public schools (in WA, managed by DNR); you should be grateful!

  Land division artifacts

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Problems with PLSS   Because the earth is an ellipsoid, rectangular divisions

will ultimately lead to discrepancies (can you cut an orange peel into squares?)

  Imposition of new system conflicted in some locations with previously existing land divisions

US Public Land Survey System (PLSS)

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  Codified in the 1930s   Based on a Cartesian coordinate system   Breaks the US up into a number of zones (124 in

US)   Most states’ zones are based on Lambert

Conformal Conic or Transverse Mercator projection

  Originally based on NAD27 datum, recently updated to NAD83 with GPS augmentation (HPGN = “High Precision GPS Network)

  Highly accurate (error < 1:10,000 within a zone)

State Plane Coordinate System (SPCS)

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Each state or division of state has its own numeric code

  Washington State has 2 zones, based on Lambert Conformal Conic projection

  North zone: 5601   South zone: 5626

State Plane Coordinate System (SPCS)

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Problems with SPCS   Each state or state subdivision uses a different zone

  Makes use of the SPCS in large areas cumbersome

  Accuracy declines outside of a zone   Makes use of the SPCS problematic when mapping &

analyzing large areas

State Plane Coordinate System (SPCS)

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  Developed by US Army Corps of Engineers in 1940s   A global system (between 80° S latitude and 84° N

latitude)   Unambiguous location for every place on earth   Based on the Transverse Mercator projection   60 zones, each 6° wide

Universal Transverse Mercator (UTM)

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Global UTM grid

Universal Transverse Mercator (UTM)

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UTM zones in the continental US

Universal Transverse Mercator (UTM)

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Comparing different coordinate systems

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Comparing different coordinate systems

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Conclusion   Knowing where things are depends on measurement

frameworks   Measurement frameworks rely on commonly

agreed-upon standards   The great thing about standards is there are so many

to choose from   Calculation of land measurements will vary by

measurement framework   Wherever you go, there you are!

Comparing different coordinate systems