DTED -- Military Elevation Data
GDAL supports DTED Levels 0, 1, and 2 elevation data for read access.
Elevation data is returned as 16 bit signed integer. Appropriate
projection and georeferencing information is also returned.
A variety of header fields are returned dataset level metadata.
Elevation data in DTED files are organized per columns. This data organization doesn't fit very well
with some scanline oriented algorithms and can cause slowdowns, especially for DTED Level 2 datasets.
By defining GDAL_DTED_SINGLE_BLOCK=TRUE, a whole DTED dataset will be considered as a single block. The
first access to the file will be slow, but further accesses will be much quicker. Only use that option if
you need to do processing on a whole file.
The DTED specification (MIL-PRF-89020B) states that
horizontal datum shall be the World Geodetic System (WGS 84). However, there are still people using old data files
georeferenced in WGS 72. A header field indicates the horizontal datum code, so we can detect and handle this situation.
- If the horizontal datum specified in the DTED file is WGS84, the DTED driver will report WGS 84 as SRS.
- If the horizontal datum specified in the DTED file is WGS72, the DTED driver will report WGS 72 as SRS and issue a warning.
- If the horizontal datum specified in the DTED file is neither WGS84 nor WGS72, the DTED driver will report WGS 84 as SRS and issue a warning.
The default behaviour of the DTED driver is to ignore the checksum while
reading data from the files. However, you may specify the environment
variable DTED_VERIFY_CHECKSUM=YES if you want the checksums to be verified.
In some cases, the checksum written in the DTED file is wrong (the data producer did a wrong job).
This will be reported as a warning.
If the checksum written in the DTED file and the checksum computed from the data do not match, an
error will be issued.
The DTED driver does support creating new files, but the input data
must be exactly formatted as a Level 0, 1 or 2 cell. That is the size,
and bounds must be appropriate for a cell.
- Implemented as gdal/frmts/dted/dteddataset.cpp.