Adding a New Grid Shift Override File
MicroStation PowerDraft CONNECT Edition contains major upgrades to the coordinate system library. As a result, the method used to configure grid shift files has changed. The UserOverrideGeodeticTransformSeed.asc file delivered in the ..\GeoCoordinateData\ folder in MicroStation PowerDraft's program directory contains entries for all geodetic transformations that currently make use of grid shift files.
To Add a New Grid Shift Override File
- Create an empty text file in the coordinate system dictionary folder ( ..\GeoCoordinateData\ ). The file must be called UserOverrideGeodeticTransform.asc.
- From UserOverrideGeodeticTransformSeed.asc, locate the section pertaining to the geodetic transformation to be overridden. Copy this section and paste it into the newly created empty file.
- Uncomment the section in the new file by removing the "#" symbol from the front of each line.
- Add an entry introducing the new grid shift file. An example for the ED50-IGN.ES datum is given below. Here we are adding an entry for a new grid file called NEW_USER_FILE.gsb.
GX_NAME: ED50-IGN.ES_to_ETRF89 SRC_DTM: ED50-IGN.ES TRG_DTM: ETRF89 DESC_NM: ED50 to ETRF89 via Grid File (Canadian NTv2 format) SOURCE: Instituto Geográfico Nacional, Spain EPSG_NBR: 0 INVERSE: Yes MAX_ITR: 10 CNVRG_VAL: 1e-09 ERROR_VAL: 5e-08 ACCURACY: 1.0 METHOD: GRID_INTERP GRID_FILE: NTv2,Fwd,.\Spain\sped2et-2005.gsb GRID_FILE: NTv2,Fwd,.\Spain\BALR2009.gsb GRID_FILE: NTv2,Fwd,.\Spain\R2009V9.gsb GRID_FILE: NTv2,Fwd,.\Spain\NEW_USER_FILE.gsb FALLBACK: ERP50-SP-EST99_to_WGS84
More details are described in the comment section of the UserOverrideGeodeticTransformSeed.asc file.