Beginning with Version 16.1, Traverse PC uses files to define Coordinate reference systems. Older version of Traverse PC used a single file named TpcZone.dat. This file held all the coordinate reference systems and their zones. TPC now separates the coordinate reference systems into their own file. In each of those files the CRS stores the approperate zones and the default horizontal datum. All the CRS files are located in the Program Data folder, the folder name is Coordinate Reference Systems.
CRS Files (3:04) - You can now add and edit CRS files in TPC Desktop
In addition to CRS files, TPC can also define a Coordinate Reference System from an ESRI Projection (.prj) file. See PRJ Files.
CRS File Syntax
TPC describes the CRS file syntax in a file named SyntaxCRS.txt and also in CRS File Sytnax.
You'll find this file in the Program Data folder. You can access it from the CRS dialog by choosing the Open Folder button.
Adding a new CRS
Adding a new CRS file for Traverse PC is easy. Navigate to the folder CoordinateReferenceSystems in your Traverse PC's version of Program Data. Create a new file with the extension (*.crs) and add the required data in that file so TPC knows how to handle the new CRS file. The name of the file will be the name that TPC uses when you're selecting a new CRS.
Removing a CRS
Removing a CRS file is straight forward. Shut down TPC if it's running and locate the CoordinateReferenceSystems folder in your Traverse PC's version of Program Data. Locate the CRS file you want to remove and delete it. Any survey you open that used that now deleted CRS file will send an error message to the Message View saying that it couldn't locate the CRS file and will now set the survey's default CRS to Local.crs. Simply change the survey's CRS to something else or leave it as Local.crs.
Editing a CRS
Editing a CRS file isn't tricky. Open the CRS file in your favorite text editor and start editing. There is a text file stored with the CRS files called: SyntaxCRS.txt. This file describes how to edit and add zones to the CRS files and should always be referenced when editing CRS files.
Look at SyntaxCRS.txt to see how to edit zones, ellipses, and units for the CRS file
The name defines a record type in the TpcZone.dat file that holds all the CRS definitions. This is a text file that you can edit to add or modify CRS components. TPC ships with the following reference systems:
Local, UTM, NAD27, NAD83 (1986) (Conus), MNCRS (Minnesota), OCRS (Oregon ), WISCRS (Wisconsin), NZGD2000 (New Zealand), CanadaMTM, Canada3TM.
Zone
A CRS can have any number of zones. Zones define a projection and datum. TPC includes the common zones for North America and world zones for UTM. Low distortion zones like OCRS and WISCRS reference systems are also included.
Ellipsoids
Ellipsoids are mathematical representations of the Earth. TPC provides several common ellipsoids like Clark 1866, GRS 1980, WGS 66, WGS 72 and WGS 84 (not to be confused with the WGS 84 datum). These are defined in the TpcEllipses.dat file in the program folder. You would not normally modify this file since you can easily edit ellipses directly from TPC.
You can easily modify the existing ellipsoids or add your own directly from TPC using the Ellipse dialog. The ellipses you create or edit are stored in the UserEllipses.dat file in your program data folder.
Horizontal Datum
A horizontal datum (datum) relate the geodetic coordinates in a CRS to the rectangular coordinates. Hundreds of datums exist around the world, each relating a geodetic coordinate to a specific rectangular coordinate. Published geodetic reference points in your area will include rectangular coordinates and the name of the datum those coordinates are based on. The datum you choose to use in your survey may be dictated by state law (statues).
Traverse includes the following horizontal datums in its TpcZone.dat file (in the program folder). UTM, NAD27, NAD83_Albers and NAD83 (Conus) or more specifically NAD83 (1986) (Conus). You can modify certain datum parameters like the false origin and reference latitudes and longitudes in the TpcZone.dat file if needed.
Horizontal Datum Shifts
TPC does not automatically shift horizontal datums. If for instance, you transform your survey from NAD83 (1986) to NAD27, you will need to manually translate the survey to a published position on the NAD27 datum.
Vertical Datum
TPC does not currently use any mathematical geoid models to compute elevations. Think of these as traditional elevations or more specifically as orthometric heights (ellipsoid height - geoid height).
Elevations are assumed to be based on the National Geodetic Vertical Datum of 1929 (NGVD 1929) which is generally considered to be mean sea level.
Conversions between geodetic and rectangular coordinates are done independent of a points elevation.
Projections
A map projection or just projection projects the ellipsoid onto a flat surface. TPC supports the following projections
•Lambert conformal conic (with 1 or 2 standard parallels)
•Transverse Mercator
•Universal Transverse Mercator
•Modified Transverse Mercator
•Oblique Mercator
•Albers (with 1 standard parallels)
The projection is defined for each zone in a CRS. So within a CRS, each zone can use the projection which best fits that zone.
