com.luciad.format.raster

LuciadLightspeedClass TLcdDEMModelDecoder

java.lang.Object

com.luciad.format.raster.TLcdDEMModelDecoder

All Implemented Interfaces:

ILcdInputStreamFactoryCapable, ILcdModelDecoder

@LcdService(service=ILcdModelDecoder.class,
            priority=20000)
public class TLcdDEMModelDecoder
extends Object
implements ILcdModelDecoder, ILcdInputStreamFactoryCapable

This model decoder decodes elevation rasters in the DEM format (USGS Digital Elevation Model).

Input files

File	Required	Entry point	Description
*.dem	x	x	DEM file containing the elevation raster

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 DEM file.
• All models returned by this model decoder implement ILcd2DBoundsIndexedModel.

Model descriptor

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

Model reference

• All models returned by this model decoder have an ILcdGeodeticReference (for geodetic systems) or an ILcdGridReference (for UTM systems) as a model reference.
• The geodetic datum of this reference is an ellipsoidal datum WGS72, WGS84, NAD27, NAD83, or, if supportGeoidDatums is set to true, a more accurate geoid datum NGVD27, NAVD88, or EGM96.

Model elements

• Each decoded model contains one object: an ALcdImage (and ILcdRaster) instance.
• 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 DEM files don't contain any color information.

Sample code

 TLcdDEMModelDecoder   decoder    = new TLcdDEMModelDecoder();
 ILcdColorModelFactory factory    = new TLcdDTEDColorModelFactory();
 ColorModel            colorModel = factory.createColorModel();

 decoder.setColorModel(colorModel);

 ILcdModel model = decoder.decode("elevations.dem");
 

Performance tips

• Since DEM rasters only provide a single level of detail, precomputing and storing multiple levels of detail may speed up visualization and some computations. For instance, the TLcdGeoTIFFModelEncoder can create compressed multilevel GeoTIFF files that can replace the original DEM files.

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

• Standards for Digital Elevation Models, US Department of the Interior, US Geological Survey, National Mapping Division, August 1997

Known limitations

• Only geographic and UTM reference systems are supported. State plane reference systems are not supported.
• Only the following datums are supported: horizontal datums NAD27, WGS72, WGS84, and NAD83, and vertical datums NVGD29, NAVD88, and EGM96. The following datums are not supported: old Hawaii and Puerto Rico.

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_DISPLAY_NAME
static String	DEFAULT_EXTENSION

Constructor Summary

Constructors

Constructor and Description
TLcdDEMModelDecoder() Creates a new TLcdDEMModelDecoder, with a globally shared buffer for caching tiles.
TLcdDEMModelDecoder(ILcdBuffer aBuffer) Creates a new TLcdDEMModelDecoder.

Method Summary

Modifier and Type	Method and Description
boolean	canDecodeSource(String aString) Checks whether this model decoder can decode the specified data source.
ILcdModel	decode(String aSourceName) Creates a new model from the given data source.
ColorModel	getColorModel() Returns the color model that is attached to decoded rasters.
String	getDisplayName() Returns a short, displayable name for the format that is decoded by this ILcdModelDecoder.
ILcdInputStreamFactory	getInputStreamFactory() Returns the input stream factory that is used for creating input streams given source names.
boolean	isSupportGeoidDatums() Returns whether the geodetic datums of the decoded model references may be geoid datums.
void	setColorModel(ColorModel aColorModel) Sets the color model that will be attached to decoded rasters.
void	setInputStreamFactory(ILcdInputStreamFactory aInputStreamFactory) Sets the input stream factory that will be used for creating input streams given source names.
void	setSupportGeoidDatums(boolean aSupportGeoidDatums) Specifies whether the geodetic datums of the decoded model references may be geoid datums (like NAVD88), instead of the default ellipsoid datums (like NAD83).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.luciad.model.ILcdModelDecoder

canDecodeSource, decodeModelMetadata, decodeModelMetadata, decodeSource, discoverDataSources

Field Detail

DEFAULT_DISPLAY_NAME

public static final String DEFAULT_DISPLAY_NAME

See Also:

Constant Field Values

DEFAULT_EXTENSION

public static final String DEFAULT_EXTENSION

See Also:

Constant Field Values

Constructor Detail

TLcdDEMModelDecoder

public TLcdDEMModelDecoder()

Creates a new TLcdDEMModelDecoder, with a globally shared buffer for caching tiles.

See Also:

TLcdSharedBuffer.getBufferInstance()

TLcdDEMModelDecoder

public TLcdDEMModelDecoder(ILcdBuffer aBuffer)

Creates a new TLcdDEMModelDecoder.

Parameters:

aBuffer - the buffer in which decoded raster tiles will be cached.

Method Detail

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.

setSupportGeoidDatums

public void setSupportGeoidDatums(boolean aSupportGeoidDatums)

Specifies whether the geodetic datums of the decoded model references may be geoid datums (like NAVD88), instead of the default ellipsoid datums (like NAD83). Geoids vary smoothly between -110m and +90m around the ellipsoid. Geoid datums are more accurate for elevation data, but they require more memory and more processing time when they are being used in transformation calculations.

isSupportGeoidDatums

public boolean isSupportGeoidDatums()

Returns whether the geodetic datums of the decoded model references may be geoid datums.

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 (ends with) "dem".

See Also:

ILcdModelDecoder.decode(String), ILcdModelDecoder.decodeModelMetadata(String)

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);
      }
   }
 

InterruptedIOException - When the thread on which this method is called is interrupted: it is recommended to stop the decoding and throw an InterruptedIOException. This same exception can also be used if the decoder shows UI to the user, and the user cancels the decoding through the UI.

See Also:

ILcdModelDecoder.canDecodeSource(String)