Transcript Projections and Datums within ArcGIS - Spatial-Ed
Projections and Datums within ArcGIS
Melita Kennedy
2012 Datum Series Sponsored by GPSMMS Subcommittee This is the third webinar in a 3-part Series on Datums.
1) Datum Primer – Dave Doyle* 2) 3) GPS Software Datums - Joel Cusick / Alison Walker (Nov 18)** Projections and Datums in ArcGIS – Melita Kennedy (Dec 17)***
Tim Smith Chair; Joel Cusick Co-Chair * http://www.anymeeting.com/tgadgets/EC51DA87854B ** - Sharepoint Site – Datum Webinars *** - This Webinar Sharepoint Site – Datum Webinars
Topics
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Esri projection engine
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Coordinate systems
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Transformations
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Future work
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Review
Esri Projection Engine
Esri projection engine
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One universal library for all ESRI products
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pe.dll
Not tied to just one product
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Improve maintenance/ease of programming
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Speed, consistent results, standardization
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Accuracy – tight forward/inverse round trips
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Must have inversibility
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Engine versus Factory
PE library sections
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Engine
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Objection creation & processing
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Transformations
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Projections
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Math functions
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Factory
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Predefined objects
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Coordinate systems, ellipsoids, units, etc
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Well-known ID lookup
Number of Objects in PE Factory
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10 57
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217 15 44 Angular Unit Linear units Spheroids Prime Meridians Parameters
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607 Datums 635 GCS
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1240 Geographic Transforms
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3567 PCS
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14 Geographic methods 2 Horizontal methods 9 Vertical methods
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117 Vertical Datums 124 VCS 47 Vertical Transformations
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74 Projections
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17 Horizontal/Vertical CS
Total = 6796 at 10.0
Number of Objects in PE Factory
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10 59
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218 15 44 Angular Unit Linear units Spheroids Prime Meridians Parameters
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644 Datums 671 GCS
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1375 Geographic Transforms
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4289 PCS
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14 Geographic methods 2 Horizontal methods 9 Vertical methods
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126 Vertical Datums 133 VCS 69 Vertical Transformations
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76 Projections
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17 Horizontal/Vertical CS
Total = 7771 at 10.1.1
Coordinate Systems
ArcGIS 10.1 coordinate systems
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Coordinate system definitions always stored in library
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‘prj files’ installed separately
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At 10.1 over 5000 files
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Now store the folder information in the library
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Display a ‘virtual’ directory structure
NAD 1983 and variant support
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GCS, UTM zones, SPCS zones, Albers
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NAD 1983
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NAD 1983 HARN
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NAD 1983 CORS96
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NAD 1983 NSRS2007
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NAD 1983 (2011) + UTM zones
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State Plane zones in 10.1.2
ArcGIS 10.1 coordinate systems
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User interface updated
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‘Layers’
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Listed each layer
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Open to see its coordinate system
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Now list each coordinate system
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Open to see which layers use it
spatial filter well-known ID search favorites create or import coordinate system
Coordinate system search and filter
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Spatial filter
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Current extent
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Layer extent (any in the map)
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Custom extent
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Search/filter by
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Name
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Only folders that contain matches will be shown
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Well-known ID (WKID) aka 4326, 26906
Favorites
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Now visible (and usable) everywhere
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Stored in your user profile
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C:\Documents and Settings\melita\Application Data\ ESRI\Desktop10.1\ArcMap\Coordinate Systems (Windows XP)
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Supports folders
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Import coordinate system from
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Data
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Prj file NEW
Coordinate System Demonstration
Transformations
Geographic transformations
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‘Datum’ transformations
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Convert between GCS
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Includes unit, prime meridian, and spheroid changes
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Defined in a particular direction
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All are reversible
Transformation methods
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Equation-based
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Molodensky, Abridged Molodensky, Geocentric Translation
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Coordinate Frame, Position Vector, Molodensky-Badekas
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Longitude Rotation, 2D lat / lon offsets
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File-based
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NADCON, HARN, NTv2
ArcMap 10.1 transformations
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Sorted by applicability
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Area of use
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Accuracy
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Will create compound (two-step) transformations automatically
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Ex. NAD_1927_To_NAD_1983_NADCON + NAD_1983_To_WGS_1984_5
Combined transformations
ArcMap 10.1.1 transformations
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NAD_1927_To_NAD_1983_NADCON
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ArcMap default
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Until 10.1.1
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No more default transformations!
Transformation metadata
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Areas of use
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Accuracy
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C:\Program Files\ArcGIS\Desktop10.1\Documentation\ geographic_transformations.pdf
http://support.esri.com/en/knowledgebase/techarticles/detail/21327
Methods in Alaska
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Coordinate Frame
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Equation-based
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Seven parameters
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3 translations, 3 rotations, 1 scale factor (in XYZ)
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NAD_1983_To_WGS_1984_5
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WGS_1984_(ITRF00)_To_NAD_1983
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NADCON / HARN
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File-based
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Generally most accurate
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NAD_1927_To_NAD_1983_Alaska
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No transformations released for current adjustments
Transformations with same parameters (1) Officially, NAD83 (CORS96) to ITRF96*
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NAD_1983_To_WGS_1984_5*
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NAD_1983_HARN_To_WGS_1984_3
Source: http://geodesy.noaa.gov/CORS/coord_info/ coordtrans_no_support_tables.shtml *Paper:
http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf
Table 1, page, 51, Last column
_5 is Default for DNRGPS And ArcGIS prior to 10.0
Transformations with same parameters (2) Officially, ITRF00 to NAD83 (CORS96)
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ITRF_2000_To_NAD_1983_CORS96
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ITRF_2000_To_NAD_1983_HARN
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ITRF_2000_To_NAD_1983_2011
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WGS_1984_(ITRF00)_To_NAD_1983_HARN
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WGS_1984_(ITRF00)_To_NAD_1983_CORS96
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WGS_1984_(ITRF00)_To_NAD_1983_2011
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WGS_1984_(ITRF00)_To_NAD_1983
Source: http://geodesy.noaa.gov/CORS/coord_info/ coordtrans_no_support_tables.shtml
NGS CORS past coordinates website
http://geodesy.noaa.gov/CORS/coord_info/coordtrans_no_support_tables.shtml
Paper:
http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf
Table 2, page, 52
Transformations with same parameters (3) ITRF08/WGS84 transformations
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ITRF_2008_To_NAD_1983_2011
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WGS_1984_(ITRF08)_To_NAD_1983_2011 Pacific Plate
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ITRF_2008_To_NAD_1983_PA11
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WGS_1984_(ITRF08)_To_NAD_1983_PA11 Marianas Plate
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ITRF_2008_To_NAD_1983_MA11
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WGS_1984_(ITRF08)_To_NAD_1983_MA11
Source: http://www.ngs.noaa.gov/CORS/coords.shtml
NGS CORS coordinates website
http://www.ngs.noaa.gov/CORS/coords.shtml
Bookkeeping transformations Parameters are zeroes!
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ITRF_2000_To_WGS_1984
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NAD_1983_CORS96_To_NAD_1983_HARN
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NAD_1983_CORS96_To_NAD_1983_NSRS2007
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NAD_1983_CORS96_To_NAD_1983_2011
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NAD_1983_HARN_To_NAD_1983_NSRS2007_1
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NAD_1983_HARN_To_NAD_1983_2011
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NAD_1983_NSRS2007_To_NAD_1983_2011
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NAD_1983_NSRS2007_To_WGS_1984_1
Geographic Transformation Demonstration
Current and Future Work
Geodetic features
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Editing
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Advanced Editing toolbar
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Lines, circles, and ellipses
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Geoprocessing Tools
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Bearing Distance to Line
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XY to Line
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Table to Ellipse
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Buffer
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Geographic coordinate system
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Calculate Grid Convergence Angle
Geodetic features
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Types
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Geodesic
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Great circle / great elliptic
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Rhumb line / loxodrome
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Normal section
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Measure tool
Future work
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Vertical transformations
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Customizable ‘factory’
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Limited selection of coordinate systems and transformations
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14 parameter (time-based) datum transformations
Vertical transformation methods
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Vertical Offset
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Vertical Offset and Slope
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VERTCON
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Geoid models
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EGM84, EGM96, EGM2008
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US geoid models
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Generic model/file type for user-defined ones
14 parameter time-based transformation
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Base 7 parameters are updated based on velocity values
Review
WGS84/ITRF Sats
Review:Datums Change
ITRF00 Base Provider Export Using NAD83(CONUS)CORS96 GIS
SSF COR SHP
How to Do it
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In Garmin Workflows with DNRGPS (Formerly DNRGarmin)…
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Tag all your data as “plain vanilla” “NAD83” Exported Coordinate System:
Alaska Albers
Use this POSC Code: Use this PRJ
3338 UTM Zone 8 GCS NAD83 26908 4269 (no projection NAD 1983 Alaska Albers (Meters).prj
NAD 1983 UTM Zone 8N.prj
GCS NAD 1983.prj
How to Do it
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In Pathfinder Office, select the Projection file to match the Exported Coordinate System.
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Today tag your CORS corrected data to “CORS96” NAD83 Use this PRJ File: Exported Coordinate System:
Alaska Albers UTM Zone 8 GCS NAD83 NAD 1983 (CORS96) Alaska Albers (Meters).prj
NAD 1983 (CORS96) UTM Zone 8N.prj
NAD 1983 (CORS96) prj
How to Do it
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In ArcGIS *Assuming the standards of how the data “got to NAD83” were followed… Convert from: Into GCS_NAD_1983_CORS96 use:
GCS_North_American_1983 None GCS_WGS_1984 Garmin/DNRGPS: Go Into GCS_NAD83 only GCS_North_American_1983_HARN Mapping Grade: WGS_1984_(ITRF00)_To_NAD_1983_CORS96 NAD_1983_CORS96_To_NAD_1983_HARN
Conclusions
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As spatial references continue to evolve, it is important to understand how such evolution affects the Mapping software that we use for collecting and processing GPS data.
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As we navigate to previous GPS datasets or update them (at submeter), it is extremely important to transform properly to get back to the right place
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Options in the field and office GPS software can change the spatial reference of the GPS data that we collect.
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Esri software options can also change the spatial reference of any GPS data we collect.
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Knowing how these changes occur can eliminate much confusion and lead to satisfactory positioning results.
References
• Soler, T. & R.A. Snay (2004). Transforming positions and velocities between the International Terrestrial Reference Frame of 2000 and North American Datum of 1983,
J. Surv. Engrg., ASCE
, 130(2), 49-55. http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf
• Trimble , “GPS Pathfinder Office Software or the GPS Analyst Extension: Resolving the NAD 83 Datum Transformation Issue ,” [online]. http://trl.trimble.com/docushare/dsweb/Get/Document 170369/SprtNote_PFOGPSA_NAD83Datum.pdf
• Dr. Richard Snay is Retired Manager of the National Continuously Operating Reference Station (CORS) program and a geodesist with the National Geodetic Survey • http://support.esri.com/en/knowledgebase/techarticles/detail/ 21327
Questions?
Thank you!