Package com.luciad.format.raster

Class TLcdDTEDModelDecoder

java.lang.Object
com.luciad.format.raster.TLcdDTEDModelDecoder
All Implemented Interfaces:
ILcdInputStreamFactoryCapable, ILcdModelDecoder
@LcdService(service=ILcdModelDecoder.class, priority=20000) public class TLcdDTEDModelDecoder extends Object implements ILcdModelDecoder, ILcdInputStreamFactoryCapable
This model decoder decodes individual DTED (Digital Terrain Elevation Data) files.

Input files

File Required Entry point Description
*.dt[012] x x DTED file corresponding to a single cell of 1 degree by 1 degree

Supported file transfer protocols

  • This model decoder supports all transfer protocols that are supported by the inputStreamFactory of this decoder.

Model structure

  • This model decoder creates a model per DTED file.
  • All models returned by this model decoder implement ILcd2DBoundsIndexedModel.

Model descriptor

  • All models returned by this model decoder have a TLcdDTEDModelDescriptor.
  • The type name of the model descriptor is the display name of this decoder.

Model reference

  • All models returned by this model decoder have instances of ILcdGeodeticReference as model references.
  • The geodetic datum of this reference is geoid datum EGM96. if supportGeoidDatums is set to false, a less accurate ellipsoidal datum WGS72 or WGS84 will be used.

Model elements

  • Each decoded model contains one object: an ALcdImage (and ILcdRaster) instance.
  • The ILcdRaster instance in turn contains a single TLcdDTEDTile instance that corresponds to the DTED cell and that points to additional information about the cell.
  • The decoded elevation data is always point-sampled. This is however only exposed via the ALcdImage interface. Legacy rasters are assumed to be area-sampled.

Useful settings

  • The property colorModel allows to override the default 16-bits index color that is attached to the decoded rasters, since DTED files don't contain any color information.
  • The decoded raster contains the elevation values from the corresponding DTED cell. By default, the rasters contain tiles with piece-wise constant pixel values, without any interpolation (sometimes referred to as "Pixel-is-Area"). However, the original DTED cells contain discrete sample points (sometimes referred to as "Pixel-is-Point"). The way in which a tile value is derived from the DTED can be specified by means of the sampleStrategy property. For instance, a tile value can be a corner value, or the minimum, maximum, or average of the four corner values. Furthermore, the raster values can be derived by means of bilinear interpolation. This yields better-looking results, at a higher computational cost.

Sample code


 TLcdDTEDModelDecoder decoder = new TLcdDTEDModelDecoder();

 ILcdModel model = decoder.decode("dted/e011/n45.dt0");

Performance tips

Thread safety

  • The decoding of models is thread-safe, as long as no properties are changed during the decoding.
  • The decoded models and elements are thread-safe for read access, on the condition that a thread-safe buffer is used.

Supported versions and specifications

  • MIL-D-89020B, Digital Terrain Elevation Data (DTED), NIMA, 23 May 2000
See Also:

  • Field Details

    • DEFAULT_DISPLAY_NAME

      public static final String DEFAULT_DISPLAY_NAME
      See Also:

    • SHADING_DISPLAY_NAME

      public static final String SHADING_DISPLAY_NAME
      See Also:

    • DEFAULT_EXTENSIONS

      public static final String[] DEFAULT_EXTENSIONS

    • NORTH_WEST_CORNER

      public static final int NORTH_WEST_CORNER
      The sampling strategy that returns the North-West corner of each DTED sample cell.
      See Also:

    • SOUTH_WEST_CORNER

      public static final int SOUTH_WEST_CORNER
      The sampling strategy that returns the South-West corner of each DTED sample cell.
      See Also:

    • NORTH_EAST_CORNER

      public static final int NORTH_EAST_CORNER
      The sampling strategy that returns the North-East corner of each DTED sample cell.
      See Also:

    • SOUTH_EAST_CORNER

      public static final int SOUTH_EAST_CORNER
      The sampling strategy that returns the South-East corner of each DTED sample cell.
      See Also:

    • MINIMUM

      public static final int MINIMUM
      The sampling strategy that returns the minimum value of the corners of each DTED sample cell.
      See Also:

    • MAXIMUM

      public static final int MAXIMUM
      The sampling strategy that returns the maximum value of the corners of each DTED sample cell.
      See Also:

    • AVERAGE

      public static final int AVERAGE
      The sampling strategy that returns the average value of the corners of each DTED sample cell.
      See Also:

    • BILINEAR

      public static final int BILINEAR
      The sampling strategy that returns a bilinear interpolation of the values of the corners of each DTED sample cell.
      See Also:

  • Constructor Details

    • TLcdDTEDModelDecoder

      public TLcdDTEDModelDecoder()
      Creates a model decoder to decode DTED files, with a globally shared buffer for caching tiles.
      See Also:

    • TLcdDTEDModelDecoder

      public TLcdDTEDModelDecoder(ILcdBuffer aBuffer)
      Creates a model decoder to decode DTED files.
      Parameters:
      aBuffer - the buffer in which decoded raster tiles are cached.

    • TLcdDTEDModelDecoder

      public TLcdDTEDModelDecoder(ILcdBuffer aBuffer, boolean aShading)
      Creates a model decoder to decode DTED files, optionally producing shaded rasters instead of elevation rasters.
      Parameters:
      aBuffer - the buffer in which decoded raster tiles are cached.
      aShading - specifies whether rasters should be shaded.

  • Method Details

    • setInputStreamFactory

      public void setInputStreamFactory(ILcdInputStreamFactory aInputStreamFactory)
      Sets the input stream factory that will be used for creating input streams given source names.
      Specified by:
      setInputStreamFactory in interface ILcdInputStreamFactoryCapable
      Parameters:
      aInputStreamFactory - the input stream factory to be used.

    • getInputStreamFactory

      public ILcdInputStreamFactory getInputStreamFactory()
      Returns the input stream factory that is used for creating input streams given source names.
      Specified by:
      getInputStreamFactory in interface ILcdInputStreamFactoryCapable
      Returns:
      the input stream factory that is used.

    • setColorModel

      public void setColorModel(ColorModel aColorModel)
      Sets the color model that will be attached to decoded rasters.
      Parameters:
      aColorModel - a 16-bit IndexColorModel.

    • getColorModel

      public ColorModel getColorModel()
      Returns the color model that is attached to decoded rasters.

    • setSampleStrategy

      public void setSampleStrategy(int aSampleStrategy)
      Sets the sampling strategy for retrieving elevation values. This setting is only relevant when accessing the DTED model via the ILcdRaster API. The ALcdImage API explicitly models DTED data as being point-sampled and will ignore this setting.
      Parameters:
      aSampleStrategy - one of NORTH_WEST_CORNER, SOUTH_WEST_CORNER, NORTH_EAST_CORNER, SOUTH_EAST_CORNER, MINIMUM, MAXIMUM, AVERAGE, or BILINEAR.

    • getSampleStrategy

      public int getSampleStrategy()

    • setSupportGeoidDatums

      public void setSupportGeoidDatums(boolean aSupportGeoidDatums)
      Specifies whether the decoded geodetic datum of the geodetic reference should be a geoid datum (EGM96), or an ellipsoid datum (WGS84 or WGS72). The geoid varies smoothly between -110m and +90m around the ellipsoid. The geoid datum is more accurate, but it requires more memory and more processing time when it is being used in transformation calculations.

      The default value is true.

    • isSupportGeoidDatums

      public boolean isSupportGeoidDatums()
      Returns whether the geodetic datums of the model references may be geoid datums.

      The default value is true.

    • setApplyGeoidDatums

      public void setApplyGeoidDatums(boolean aApplyGeoidDatums)
      Specifies whether the geoid heights of the geodetic datum (EGM96) should be added to the elevation data right away while decoding. The geoid varies smoothly between -110m and +90m around the ellipsoid. The geodetic datum of the geodetic reference will then be an ordinary ellipsoid datum (WGS84 or WGS72). Decoded rasters will be more accurate, but the operation requires more memory and more processing time while decoding the elevation data (which is still done lazily).

      This is an alternative to setSupportGeoidDatums(boolean). It has precedence if both options are set.

      Note that the 0m elevation (sea level) becomes the geoid height, which may be confusing when a raster is displayed with an elevation color model that assigns blue colors to negative elevations.

      The default is false.

    • isApplyGeoidDatums

      public boolean isApplyGeoidDatums()

    • getDisplayName

      public String getDisplayName()
      Description copied from interface: ILcdModelDecoder
      Returns a short, displayable name for the format that is decoded by this ILcdModelDecoder.
      Specified by:
      getDisplayName in interface ILcdModelDecoder
      Returns:
      the displayable name of this ILcdModelDecoder.

    • canDecodeSource

      public boolean canDecodeSource(String aString)
      Description copied from interface: ILcdModelDecoder
      Checks whether this model decoder can decode the specified data source. It is acceptable for this method to return true for a source name while decode throws an exception for that same source name.

      For performance reasons, we strongly recommend that this will only be a simple test. For example: check the file extension of a file, but not that the file exists or contains expected content.

      Specified by:
      canDecodeSource in interface ILcdModelDecoder
      Parameters:
      aString - the data source to be verified; typically a file name or a URL.
      Returns:
      true if file name aString has extension "dt0", "dt1", "dt2", "dted", "avg", "min", or "max".
      See Also:

    • decode

      public ILcdModel decode(String aSourceName) throws IOException
      Description copied from interface: ILcdModelDecoder
      Creates a new model from the given data source.
      Specified by:
      decode in interface ILcdModelDecoder
      Parameters:
      aSourceName - the data source to be decoded; typically a file name or a URL.
      Returns:
      A model containing the decoded data. While null is allowed, implementors are advised to throw an error instead.
      Throws:
      IOException - for any exceptions caused by IO problems or invalid data. Since decoding invalid data almost always results in RunTimeExceptions (NullPointerException, IndexOutOfBoundsException, IllegalArgumentException, ...) on unexpected places, implementations are advised to catch RuntimeExceptions in their decode() method, and wrap them into an IOException, as illustrated in the code snippet below. 
      
   public ILcdModel decode( String aSourceName ) throws IOException {
      try (InputStream input = fInputStreamFactory.createInputStream(aSourceName)) {
         // Perform decoding ...
      } catch (RuntimeException e) {
         throw new IOException(e);
      }
   }
      See Also:

    • decodeModelMetadata

      public TLcdModelMetadata decodeModelMetadata(String aSourceName) throws IOException
      Decodes metadata for the specified DTED file. If the DTED file follows the standard DTED naming conventions, this method does not do any I/O, as all metadata can be extracted from the file's source name alone. If that is not the case, this method will attempt to read the file header in order to retrieve its metadata.
      Specified by:
      decodeModelMetadata in interface ILcdModelDecoder
      Parameters:
      aSourceName - the DTED file for which metadata will be decoded.
      Returns:
      the model metadata for the given DTED file.
      Throws:
      IOException - if the metadata cannot be decoded for some reason.
      See Also: