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

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

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

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

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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.

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

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.

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

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

NAD 83 What? Rostport, Pa Year N (PA SPC) E (PA SPC) Lat Lon KX2372(2011) 326082.02 1387517.22 40 12 34.82640 079 49 49.31661 KX2372(2007) 326082.04 1387517.17 40 12 34.82655 079 49 49.31730 KX2372(1993) 1387517.15 40 12 34.82633 079 49 49.31750 KX2372(1992) 326082.05 40 12 34.82664 079 49 49.31751 KX2372(1986) 326082.80 1387517.41 40 12 34.83413 079 49 49.31433 The Earth hasn’t moved and the stake in the ground hasn’t moved so why the change? 1937 NAD27 1997 NAD83 Give a prize for guesses.

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” http://www.transportation.wv.gov/highways/programplanning/planning/grant_administration/wvtrails/Pages/gps.aspx Cartesian Coordinates for measuring distance

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

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 10-120 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. http://edndoc.esri.com/arcobjects/9.2/NET/shared/geoprocessing/coverage_toolbox/transforming_between_nad27_and_nad83.htm 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.

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

NAD 83 – Which One? WHY the difference, WHAT changed? Epochs = Adjustments NAD83 or NAD83 CONUS = 1986 adjustment included NO GPS NAD83 HARN = 1992-1993 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 NAD27 1997 NAD83 Give a prize for guesses.

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

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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

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?

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 2011. 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 1984. 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

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.

Where Datums Matter Trimble (other GPS) 3. GPS - Autonomous, WAAS, or VRS each field software has slightly different workflow. a. ArcPad b. ArcMobile http://positionsblog.trimble.com/?p=234 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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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)

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 NAD83 2011 VRS = NAD83 2011 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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 NAD83 2011 You can change the datum of your data depending on the settings under real time settings!! In order to read NAD83 2011 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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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

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 NAD83 2011 National Park Service - Pacific Islands GIS Field Technical Support Center

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

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 (1596-1650) introduced systems of coordinates based on orthogonal (right angle) coordinates.

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

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

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.

Questions Questions Christine Iksic cmi@laserinst.com 412-512-5665