Adding Grid Shift Files (TIFF/GTX/GSB)
Sometimes the Well-Known Text (WKT) of one of the coordinate systems in your project references a particular grid shift file that was not bundled with your installation, or the reference itself is missing from the WKT. The steps below describe how to add the missing grid shift inforation information in both of these cases.
Vertical datum grid shift files in TIFF/GTX formats are used to shift and transform between vertical coordinate systems that include different vertical datums, i.e., reference coordinate surfaces used for vertical positions. This is accomplished, by offsetting the vertical input coordinates by a specific amount determined by the loaded grids. Some vertical coordinate system transformations also entail the use of GSB (Binary Grid Shift) files, e.g., when converting between the NAD27, ATS77, NAD83 (Original), and NAD83 (CSRS) geodetic reference systems. For more information click here.
- Download the required TIFF/GTX/GSB file.
Note: Click here to download a self-installing TerraExplorer TEZ file (for TerraExplorer users), or here (for other Skyline applicatipons or versions of TerraExplorer below 7.3.0) to download the corresponding ZIP, that includes most common grid shift files.Additional grid shift files can be found on these websites: - Extract the ZIP and copy the grid shift files into the proj subdirectory under the product’s application files directory, e.g., C:\Program Files\Skyline\TerraExplorer Pro\proj\RAF18.gtx
- Add the references within the WKT as follows. See example below.
- Add the TIFF or GTX reference at the VERT_DATUM object that is under the VERT_CS object.
- Add the GSB reference under the DATUM object that is under the PROJCS object.
COMPD_CS["Belge 1972 / Belgian Lambert 72 + Ostend height",
PROJCS["Belge 1972 / Belgian Lambert 72", PROJCS["Belge 1972 / Belgian Lambert 72",
GEOGCS["Belge 1972",
DATUM["Reseau_National_Belge_1972"
SPHEROID["International 1924", 6378388, 297,
AUTHORITY["EPSG","7022"]],
EXTENSION["PROJ4_GRIDS", "bd72lb72_etrs89lb08.gsb"],
AUTHORITY["EPSG","6313"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4313"]],
PROJECTION["Lambert_Conformal_Conic_2SP"],
PARAMETER["standard_parallel_1",51.16666723333333],
PARAMETER["standard_parallel_2",49.8333339],
PARAMETER["latitude_of_origin",90],
PARAMETER["central_meridian",4.367486666666666],
PARAMETER["false_easting",150000.013],
PARAMETER["false_northing",5400088.438],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["X",EAST],
AXIS["Y",NORTH],
AUTHORITY["EPSG","31370"]],
VERT_CS["Ostend height",
VERT_DATUM["Ostend",2005,
EXTENSION["PROJ4_GRIDS", "us_noaa_g1999u03.tif"],
AUTHORITY["EPSG","5110"]],
UNIT["metre",1,
["EPSG","9001"]],
AXIS["Up",UP],
AUTHORITY["EPSG","5703"]]]
