Some of the NADCON grids, their areas of use, and source datums are shown in the following table.
| Shift File Name | Area | Source Datum | Accuracy at 67% confidence (m) |
|---|---|---|---|
| CONUS | Conterminous U S (lower 48 states) | NAD27 | 0.15 |
| ALASKA | Alaska, incl. Aleutian Islands | NAD27 | 0.5 |
| HAWAII | Hawaiian Islands | Old Hawaiian (4135) | 0.2 |
| STLRNC | St. Lawrence Is., AK | St. Lawrence Island (4136) | -- |
| STPAUL | St. Paul Is., AK | St. Paul Island (4137) | -- |
| STGEORGE | St. George Is., AK | St. George Island (4138) | -- |
| PRVI | Puerto Rico and the Virgin Islands | Puerto Rico (4139) | 0.05 |
Grid shift files come in two formats: binary and text. The files from the NGS are binary and have {@code .las} (latitude shift) and {@code .los} (longitude shift)extentions. Text grids may be created with the NGS nadgrd program and have {@code .laa} (latitude shift) and {@code .loa} (longitude shift) file extentions.Both types of files may be used here.
The grid names to use for transforming are parameters of this {@link MathTransform}. This parameter may be the full name and path to the grids or just the name of the grids if the default location of the grids was set as a preference. This preference may be set with the main method of this class.
Transformations here have been tested to be within 0.00001 seconds of values given by the NGS ndcon210 program for NADCON grids. American Samoa and HARN shifts have not yet been tested. References:
| |