You can use the DTED® file reader
to read Digital Terrain Elevation Data (DTED
format) files. The DTED read format is a map format for
representing terrain elevations published by the U.S. National
Imagery and Mapping Agency (NIMA). The DTED files contain digital
terrain models as rasters. A raster is a georeferenced grid
containing a value in each of its cells. In the case of DTED, and a
digital terrain model in general, the value indicates the average
elevation in the cell. However, this value can indicate any other
attribute: surface temperature, surface pressure, nitrogen rating
of the soil, and so on.
The DTED reader provided in this package is
based on the specification document MIL-PRF-89020A of 19 April
1996. DTED files are available with various precision levels,
called DTED0, DTED1, and DTED2. A DTED file contains a digital
terrain model raster that covers a zone of one degree by one
degree. The cell size of the raster depends on the DTED level:
- DTED0 provides raw data (approximately 30 to 40 KB for a file).
- DTED1 provides data that is more detailed.
- DTED2 is the most precise level. It has surface cells that are nine times smaller than those of DTED1. At this degree of precision, a DTED file is enormous (several megabytes).
The complete source code for a DTED
demonstration can be found at
The DTED raster reader
The following code shows how to use an IlvRasterDTEDReader to load a single DTED
file using the IlvMapDataSource:
IlvRasterDTEDReader r = new IlvRasterDTEDReader();
try {
r.addMap(filename);
} catch (IOException e1) {
e1.printStackTrace();
}
IlvMapDataSource source =
IlvRasterDataSourceFactory.buildImageDataSource(manager, r, null);
try {
source.start();
} catch (Exception e) {
e.printStackTrace();
}
The following code shows how to read a set of DTED files using an
IlvTiledRasterDataSource. This produces an
IlvMapLayer containing an IlvTiledLayer holding the tiles.
IlvRasterDTEDReader r = new IlvRasterDTEDReader();
try {
r.addMap(filename);
} catch (IOException e) {
e.printStackTrace();
}
IlvMapDataSource source =
IlvRasterDataSourceFactory.buildTiledImageDataSource(manager, r, true, true, null);
try {
source.start();
} catch (Exception e) {
e.printStackTrace();
}
Classes for reading the DTED format
The main class for reading DTED formats is IlvDTEDReader. This class implements the IlvMapFeatureIterator interface and returns
only one
IlvMapFeature
object, which is the raster corresponding to the digital terrain
model (DTM) stored in the file. The geometry of this map feature
is of type IlvMapRaster. The map feature has no
attribute. The projection of the reader is the source projection
of the DTED data, that is, the geographic projection.
The IlvDTEDLayer class defines load-on-demand
for the DTED format. Load-on-demand is implemented
on a DTED-level basis from the corresponding file name or URL. In
other words, the size of a tile in a JViews Maps tiled layer
corresponds to the size of a DTED tile. This specific
implementation of load-on-demand works exclusively with maps
drawn with the geographic projection. Specifying a URL allows you
to access one of the NIMA CDs directly from their website. For an
example, see the DTED demonstration at the following location: