1. LOST IN TRANSFORMATION
WVGIS 2014 Conference
June 2-5, 2014
Christine Iksic
A quick overview of coordinate systems, datums and their relationship with the way you collect data using space-based technologies and align those data with other data in a GIS.
Once we have learned there are differences it will be important to learn how to Identify what you got and Make it Match

2. Agenda Coordinate Sytems Basics – WV SPC NAD 83 (what?)
3 Places Where Datums Matter Most
Projections in ESRI
Transformations in ESRI
Datums & VRS Networks
Checking In with NGS – DSWorld in

3. Projections
 Peter H. Dana, The Geographer's Craft Project, Department of Geography, The University of Colorado at Boulder.

4. Coordinate Systems
All US states have adopted their own specialized coordinate systems
Some states use multiple zones
Several different types of projections are used by the system
Provides less distortion than UTM
Used for applications needing very high accuracy, such as surveying

5. Coordinate Systems
Coordinate systems are slippery… even if coordinates precise coordinates difficult to be certain
Coordinate systems assign a unique “address” to every point on Earth.
Coordinates are expressed relative to a datum.
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

6. Datums Building of a Map Ellipsoids and Geoids Datums Projections
Unprojected
Projected
Coordinate
Systems
UTM
Lat/Long
State Plane
In order to define where we are create a model of the earth – understanding these components to is crucial to GIS and GPS – they give our data meaning.

7. Datums
A datum specifies the earth-model (ellipsoid), and the origin associated with a particular set of coordinates.
It’s a function of a projection.
Datums provide the link between the earth and coordinate systems.
Without a datum, coordinates have no meaning.
There are many datums used worldwide.
Only one datum, WGS-84, is global, the rest are regional.
Characterized by:
A set of physical monuments, related by survey measurements and resulting coordinates (horizontal and/or vertical) for those monuments

8. What is a Datum?
Coordinates are expressed relative to a datum, and that a datum can be thought of as the point-of-origin for a map’s coordinate values, just like the 0,0 point on an XY graph. Furthermore, each datum will have a different point-of-origin because it is based on a different spheroid, or “model” of Earth’s size and shape.
NAD 27 is a local datum for North America and has it’s origin in on the surface of the earth - Kansas. More recently, NAD 83 & WGS 84 are earth centered datum’s and used satellite measurements for determining center of the earth and spheroid shape.

9. What Language is your data speaking in?
ITRF 00
NAD 27
GRS 80
WGS 84
NAVD 88
CORS
NGVD 29
NAD 83

10. NAD 83 What? Who? Huh? NGS Datasheet
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

11. NAD 83 What? Rostport, Pa Year N (PA SPC) E (PA SPC) Lat Lon
KX2372(2011)
KX2372(2007)
KX2372(1993)
KX2372(1992)
KX2372(1986)
The Earth hasn’t moved and the stake in the ground hasn’t moved so why the change? 1937 NAD NAD83
Give a prize for guesses.

12. Why it Matters Example - WVDOT Geo Spatial Policy
“Henceforth, geospatial coordinates are to be collected utilizing technology capable of a 1-meter level of accuracy. .Techniques such as GPS or conventional surveying should be used to obtain positions at accuracies greater than 1 meter. GPS should be used to obtain positions at the highest possible accuracy.. The recommended standard for representing and reporting geospatial data is as follows”
Cartesian Coordinates for measuring distance

13. Datum Shifts 350m 150m 650m 610m Map Corner NAD83
NAD83 Coordinates = 150m, 610m
610m
150m
4789
541
4790
542
NAD27 Coordinates = 350m, 650m
Map Corner
NAD27
4789
541
4790
542
650m
350m

14. Datum Shift WGS 84 NAD 83 (2011) NAD 27 10 – 120+ meters 1 meter
The only datums they are likely to use are the three represented here. The difference between NAD83 and NAD27 is about meters unprojected. Once projected, that distance is can swell a lot. So that’s why on the next slide the difference is more than 120 meters, because it was calculated using UTM.
Nearly all published statements about the amount of shift between NAD27 and NAD83 are shifts measured in meters on unprojected (latitude–longitude) data. When two datasets are projected into planar coordinates (such as UTM or State Plane) and the differences between locations in NAD27 and NAD83 are measured, the y coordinate is often approximately 200 meters larger than expected. This is a result of the difference between the size and origin of the two spheroids on which the data is being projected.
To see this for yourself, you can create a coverage of a single arc, running along a meridian from the equator to your point of interest in the coterminous United States. By default, it will be created on the Clarke 1866 spheroid. Now Project it and change the datum to NAD83. The arc should be approximately 200 meters longer.

15. How Much? ∆N ∆E total dist difference 86-11 0.78 0.19 0.80
US Survey Feet
difference 86-92
0.75
0.27
difference 92-93
0.03
0.00
difference 93-07
-0.02
difference 07-11
0.02
-0.05
0.06
Cartesian Coordinates for measuring distance

16. NAD 83 – Which One?
WHY the difference, WHAT changed? Epochs = Adjustments
NAD83 or NAD83 CONUS = 1986 adjustment included NO GPS
NAD83 HARN = adjustment were High Accuracy Reference Network (HARN); done state by state; differences between border areas
NAD83 CONUS CORS 96 - passive
NAD83 (NSRS2007) = 2007 adjustment GPS data only
NAD83 (2001)= 2011 adjustment CORS stations readjusted and held fixed as primary control
The Earth hasn’t moved and the stake in the ground hasn’t moved so why the change? 1937 NAD NAD83
Give a prize for guesses.

17. NETWORK STATUS HPGN/HARN & STATEWIDE 1991 1993 1995 1991 1996 1992
GPS222
1996
1992
1991
1996
GPS341
GPS1048
GPS197
1996
1991
reos 7/96
1993
GPS805
GP S291
GPS1047
GPS941
1994
reos-1996
reobs 9/97
1994
GPS606
1995
1996
GPS730
1992
GPS1121
1995
GPS404
1994
GPS887
1997
1997
GPS882
GPS394
1991
GPS
GPS260
1997
GPS1178
1992
GPS633
1997
1200
1995
1993
1992
GPS1179
GPS1150
1993
GPS908
GPS610
GPS412
reos-6/95-GPS904
GPS611
1995
1992
GPS419
1997
1990
-GPS120
GPS376
1993
GPS1133
GPS852
1993
1992
1994
GPS725
1992
GPS366
GPS721
GPS585
1992
1990
This slide shows the date for each HARN network in that state.-you can see the plethora of dates and since readjustments followed the HARN, how difficult it was to deal with cross-boundary issues for early and later HARN projects.
GPS383
reos 1/96 GPS936
GPS450
-GPS170
1993
GPS667
1997
GPS & CLASSICAL ADJUSTMENTS COMPLETED .
GPS ADJUSTMENT COMPLETED
GPS577

18. Where Datums Matter ESRI Trimble (other GPS) Data Frame Properties
Geodatabase / Layers
Trimble (other GPS)
3. GPS
a. Autonomous vs. Differential Correction
ArcPad
ArcMobile
TerraSync, TerraFlex, others
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

19. Transformations & Projections
Esri provides form controls for selecting the coordinate system (geographic or projected) for a feature class and also for the data frame of a map document in ArcMap and ArcCatalog.  When the datums differ, you are prompted for a datum transformation in ArcMap.
Data Frame – select projection (prj)
Layers – define projection (prj)
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

20. Projections – ESRI 10.1 newer
Don’t change your data – only changes the label!!!

21. Transformations What do you select, Yes, No, or Transformations?
Doesn’t change the data in the database, the original database. Only tells ESRI which translation/transformation to use to get to appear the same as the data frame. It does not automatically know which transformation to select. To ensure data alignment you should always be manually selecting the correct transformation.
What do you select, Yes, No, or Transformations?

22. Transformations
Defined in one direction but are inversible – use in either direction.
_1, _2,_3, _4, _5 indicates ordered they were defined.
_5 most common to CONUS
Select correct transformation everytime.
Prior to 10.1 ESRI had no transformation available to NAD83 CORS 96 or NAD83 HARN was the closest. Today ESRI is current with NGS.
A geographic transformation is always defined in a particular direction, like from NAD 1927 to WGS Transformation names will reflect this: NAD_1927_To_WGS_1984_1. The name may also include a trailing number, as the above example has _1. This number represents the order in which the transformations were defined. A larger number does not necessarily mean a more accurate transformation. Even though a geographic transformation has a built-in directionality, all transformation methods are inversible. That is, a transformation can be used in either direction

23. Transformations From Layers Datum To Data Fram Datum
Doesn’t change the data in the database, the original database. Only tells ESRI which translation/transformation to use to get to appear the same as the data frame. It does not automatically know which transformation to select. To ensure data alignment you should always be manually selecting the correct transformation.

24. Where Datums Matter Trimble (other GPS)
3. GPS - Autonomous, WAAS, or VRS
each field software has slightly different workflow.
a. ArcPad
b. ArcMobile
c. TerraSync, TerraFlex, others
Todays Demo / Instruction
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

25. GPS’ Coordinate System
GPS Ellipsoid: GRS-80
(Geodetic Reference System 1980)
GPS Datum: WGS-84
(World Geodetic System 1984)
WGS84 (G1674) – most current version
GPS Coordinate System: ECEF
(Earth Centered Earth Fixed)

26. WAAS or Autonomous GPS = WGS84
GPS Datums
Autonomous GPS = WGS84 ITRF 00
Differential Correction or VRS Real Time Correction will shift data to the reference frame and datum of correction source. Verify!
WVVRS and KeyNetGPS both NAD
VRS = NAD
WAAS or Autonomous GPS = WGS84
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

27. GPS Settings – Autonomous or WAAS
Autonomous GPS = WGS84 ITRF 00
No matter what you set coordinate system to in collector raw data in file is WGS84 ITRF00
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

28. GPS w/ VRS or Real Time Correction
Differentially corrected GPS data are always in terms of the corrections source’s reference frame.
WVVRS and KeyNetGPS both NAD
You can change the datum of your data depending on the settings under real time settings!!
In order to read NAD from the collector both the Real Time Settings Datum & Coordinate System Datum must be NAD83 (CONUS) i.e a 0 transformation
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

29. Live TerraSync Demo Setup Coordinate System Real-Time Settings
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

30. WV VRS
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

31. Checking In Verification of accuracy is essential to gain confidence
DSWorld – NGS use this NGS software to find datasheets with Google Earth.
DSWorld – link to download
Know your coordinates
Know the language your data is speaking
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

32. GPS for Ologists
Summer 2005
Post-Processing
Differentially corrected GPS data are always in terms of the corrections source’s reference frame.
Verify reference frame of differential source
Two options
Base Provider Properties = WGS84 / ITRF00
Base File (CORS) = NAD 83 (2011)
National Park Service - Pacific Islands GIS Field Technical Support Center

33. GPS for Ologists
Summer 2005
Exporting
Exporting a shapefile requires an ESRI .prj file be selected.
10.1 prj files aren’t automatically accessible
Save prj file in ESRI to Favorites
Browse to ESRI Favorites in PFO to find prj file.
Select the correct datum!
A transformation can/typically occurs here on export based on datum selected
ITRF to NAD
National Park Service - Pacific Islands GIS Field Technical Support Center

34. GPS for Ologists
Summer 2005
Common PP Workflow
Since our Reference Frame is CORS – Base Provider Properties
Our GPS data is corrected against a source that is in WGS84 or ITRF00
Export to State Plane NAD83 (2011) / Select Correct prj file
And our GIS is in NAD83(1986) or CONUS or just NAD83
We therefore define an NAD83 (2011) to NAD83 CONUS Transformation
If GIS is in WGS84 define a transformation from NAD 83 (2011) to WGS 84 (00)
National Park Service - Pacific Islands GIS Field Technical Support Center

35. Demo
Pathfinder Office Differential Correction Base Provider or Base File Option Export to proper datum Select .prj file Save prj file to Favorites in ESRI 10.1 or 10.2
Coordinate Systems are simply defined as a reference frame or system to define are starting point – we have reference frames for all three axis x, y, z
There are many basic coordinate systems familiar to students of geometry and trigonometry.
These systems can represent points in two-dimensional or three-dimensional space.
René Descartes ( ) introduced systems of coordinates based on orthogonal (right angle) coordinates.

36. Reference Frames Reference Frames CORS Post Process = ITRF00 = WGS84
GPS for Ologists
Summer 2005
Reference Frames
Reference Frames
CORS Post Process = ITRF00 = WGS84
Autonomous GPS = WGS84 = ITRF00
WAAS = ITRF00 = WGS84
NDGPS (Radio DGPS) = NAD83 (CORS96)
OMNISTAR (Satellite DGPS) = NAD83 (CORS96)
VRS (most) = NAD83 (2011)
National Park Service - Pacific Islands GIS Field Technical Support Center

37. GPS for Ologists
Summer 2005
Review
Review
Identify the proper reference frame for different differential sources – VRS and Post-Processing
Learn how to apply the correct datum transformation inside the GPS and back in the GIS.
Was there a correction or export, was there a transformation applied?
Does the prj file match the actual data (not always right.)
Tell ESRI what transformation to use. Don’t click YES.
Ask and Tell NAD 83 WHAT???!!!!
NAD83 (2011) ≠ WGS84
about 4.3 feet
National Park Service - Pacific Islands GIS Field Technical Support Center

38. DON’T GET LOST in TRANSFORMATION
Coordinate System?
Datum?
Remember, if it’s lat/long, which format? and IF UTM, what zone?
NAD83/WGS84, Fed Stand is NAD83, Pilots work in WGS84.
If we had to break the Datum shift issue into two areas where it matters most, its in the Field and in the GIS.
In the field when communicating between GPS users and when communicating or transferring data between GPS and paper maps. The classic example here is the dispatcher is in one datum and you, the user is in another datum.
In the GIS, after the data is stored and transferred into a Geographic Information system like ArcGIS.

39. Questions
Questions
Christine Iksic