Grid shift files perform datum transformation. These files contain more data points and can be modified to provide an accurate transformation over a large area.
Some common transformations with identifiers are listed in the table below:
Transformation ID | Area of Use | CRS | CRS ID | Method | Grid Shift File(s) |
RDNAP | Holland | RD New+NAP height | EPSG:7415 | RDNAPTRANS™ |
|
NTFRFG93_4807 | France | NTF (Paris) | EPSG:4807 | NTv2 |
|
NTFRFG93_4275 | France | NTF | EPSG:4275 | NTv2 |
|
EPSG:15956 | UK | OSGB 1936 / British National Grid | EPSG:27700 | OSTN |
|
EPSG:15864 | US (Alaska) | NAD27 | EPSG:4267 | NADCON |
|
EPSG:15851 | US | NAD27 | EPSG:4267 | NADCON |
|
EPSG:15786 | Australia | AGD66 | EPSG:4202 | NTv2 |
|
EPSG:5339 | UK | OSGB 1936 | EPSG:4277 | NTv2 |
|
EPSG:1693 | Canada | NAD27 | EPSG:4267 | NTv2 |
|
CARIS is installed with the following grid shift files:
• .las and .los files for the NADCON transformations from NAD27 (US)
• .grd files for the RDNAPTRANS™ transformation from RDNap (Netherlands)
• .txt file for the OSTN transformation from OSGB36 (UK)
Grid shift files from a third-party can be added to existing grids shifts. Any transformation to WGS84 using NTv2 or NADCON transformation method can be used.
1. Copy the system\Gridshifts folder to another location and install the third-party grid shift files in that folder.
2. Copy the boundcrs.dat file to another location and bind the CRS with the grid transformation to the copied boundcrs.dat file.
3. In CARIS, select Tools > Options, and in the dialog box, change Grid Shift Transformation to point to the copied folder and change the Bound Transformations environment setting to point to the copied boundcrs file. Save the new settings.
4. Close CARIS and reopen the application and select data from an area that uses the transformation.
5. Choose the Select Coordinate Reference System dialog box and view information to check that the transformation is bound to the CRS.
For example, the Coordinate Reference System, AGD66 can be bound the EPSG:15786 grid shift transformation through the boundcrs.dat file. AGD66 uses the CRS ID, EPSG:4202 and EPSG:1578 uses the A66 National (13:09.01).gsb file for Australia.
1. Both the Gridshift folder and boundcrs.dat file are copied to another location.
2. The A66 National (13:09.01).gsb file is copied to the Gridshift folder.
3. The copied boundcrs.dat file is opened and the following entry is added: AS66, EPSG:4202, EPSG:15786 where
• AS66 is the binding ID
• EPSG:4202 is the CRS ID
• EPSG:15786 is the datum ID
4. In Options dialog box, The Bound Transformations environment setting is pointed to the copied boundcrs.dat file and the Grid Transformations environment setting is pointed to the copied Grid Shifts folder.
After the modified environment settings are saved and Options dialog box is closed, CARIS is closed and reopened.
When data from Australia is displayed in CARIS, that projection can be selected using the View > Change Coordinate Reference System command.