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<html>
<head>
<title>DTED -- Military Elevation Data</title>
</head>
<body bgcolor="#ffffff">
<h1>DTED -- Military Elevation Data</h1>
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.
<p>
<h2>Read Issues</h2>
<h3>Read speed</h3>
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.
<h3>Georeferencing Issues</h3>
The DTED specification (<a href="http://earth-info.nga.mil/publications/specs/printed/89020B/89020B.pdf">MIL-PRF-89020B</a>) states that
<i>horizontal datum shall be the World Geodetic System (WGS 84)</i>. The vertical datum is defined as EGM96, or EPSG:5773. 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.
<br>
<ul>
<li>If the horizontal datum specified in the DTED file is WGS84, the DTED driver will report WGS 84 as SRS.</li>
<li>If the horizontal datum specified in the DTED file is WGS72, the DTED driver will report WGS 72 as SRS and issue a warning.</li>
<li>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.</li>
</ul>
<h3>Configuration options</h3>
<p>
This paragraph lists the configuration options that can be set to alter the default behaviour of the DTED driver.
</p>
<ul>
<li>
REPORT_COMPD_CS: (GDAL >= 2.2.2). Can be set to TRUE to avoid stripping the vertical CS of compound CS when reading the SRS of a file. Default value : FALSE
</li>
</ul>
<h3>Checksum Issues</h3>
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.
<h2>Creation Issues</h2>
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.<P>
<h2>See Also:</h2>
<ul>
<li> Implemented as <tt>gdal/frmts/dted/dteddataset.cpp</tt>.<p>
</ul>
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</html>