DAT XGD Formats
Transparent Data Access & DAT Technology
Dynamic Access Technology (DAT) is used to read and write any grid format in a way that is completely transparent to Oasis montaj. This capability enables users to display grids and images in many common third-party formats.
XGD DAT Qualifiers
The following sections document the XGD DATs supplied as part of Oasis montaj. XGD DATs are DLLs that provide interfaces to a variety of image and grid formats. Each DAT has a 3-letter identifier and a number or parameters that can be used to decorate the file name when accessing a file. For example, to access the third band of a TM image in an ER Mapper image named "City.ers", you would decorate the name as follows:
City.ers(ERM;band=3)
The first parameter in the decoration block is always the 3-letter DAT identifier, which must be supplied any time decorations are used. If decorations are not used, the default DAT type is taken from the "DAT Settings" parameter in the Advanced Settings dialog.
Each DAT also has a default input (BROWSE_IN) and output (BROWSE_OUT) decoration which is used by the browse tool in montaj to create default decorations. If you always work with specific settings for a certain DAT type, you may wish to set the appropriate decoration in the Advanced Settings dialog. The BROWSE_IN and BROWSE_OUT options are specified for each DAT.
ARC ArcView binary raster grid file (default file type *.flt) |
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DUMMY |
Dummy value used in the ArcView grid. By default this is -9999. |
BYTE ORDER |
=0 Most significant byte first =1 Least significant byte first (default) |
ORIGIN |
Origin specification in the output header (.hdr) file. =0 Use "xllcorner" and "yllcorner": bottom left corner of the lower left cell (default) =1 Use "xllcenter" and "yllcenter": center of the lower left cell. (This is the normal Geosoft definition) (This option is ignored on input, as these values are read from the header file). |
PIXEL=0 |
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PIXEL=1 |
Pixel data, displays as grid cells. |
GEOSOFT.INI section |
[DAT_ARC] |
ERM Earth Resource Mapper |
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BAND= |
Band to read/write, default band 0. If band requested is larger than bands contained in the file, the highest band will be used. If an image Cell Type is "Unsigned8BitInteger", and image has exactly three bands, it is assumed to be an RGB colour image. To read individual bands, use the BAND= parameter. |
COORDTYPE= |
RAW unknown right-handed Cartesian EN eastings and northings LATLONG latitude, longitude This parameter is only used if the ers file does not contain a coordinate block. |
TYPE= |
PlugIn Uses the ER Mapper plugin to display .alg,.ers, and .ecw files. Only the brightness can be changed in the Colour Tool. COLOR Colour output, with dummies. This is much slower that the PlugIn, but the BRT parameter is supported. RGB RGB only, no dummies. Same as COLOR except that dummy areas will be white. |
BRT= |
Brightness, 0.0 -> 2.0 (black -> white), default is BRT=1.0 Only used for RGB images. This parameter is only supported for TYPE=COLOR and TYPE=RGB. |
GEOSOFT.INI section |
[DAT_ERM] |
GRD Geosoft grid file |
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TYPE= |
data type for new files: SHORT 2-byte signed integer LONG 4-byte signed integer FLOAT 4-byte floating point COLOR 4-byte RGBd colour RGB 4-byte RGB, no dummy If not specified, the TYPE parameter in the [GRID_DAT] section of GEOSOFT.INI is used. If this is not specified, the default will be SHORT. |
For colour grids, each grid element is 4-bytes, first byte red, second byte green, third byte blue, and the fourth byte is a dummy flag. If the dummy flag is 0, the cell is transparent, otherwise the cell should be coloured. The following parameters are also meaningful for colour grids: |
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BAND=R Red band only BAND=G Green band only BAND=B Yellow band only BRT=Brightness, 0.0 -> 2.0 (black -> white), default is BRT=1.0 This only works for colour grids. DUMMY=r,g,b Dummy colour. PIXEL=0 Continuous function data (default), displays smoothly PIXEL=1 Pixel data, displays as grid cells. |
Compression: |
COMP=NONE Default - no compression of data. COMP=SPEED Compress grid data. Faster compression than "SIZE", but produces larger grid files. COMP=SIZE Compress grid data. Compresses better than "SPEED", but takes longer. Compression ratios can be improved by stripping insignificant bits from the floating-point mantisa. You can control this by appending the numver of mantisa bits required to the COMP=SIZE string. For example, COMP=SIZE12 will produce data to between 3 and 4 significant figures and achieve much better compression. Mantisa Significant |
GEOSOFT.INI section |
[DAT_GRD] BROWSE_IN="GRD" BROWSE_OUT="GRD" "GRD;Type=Byte" "GRD;Type=Short" "GRD;Type=Long" "GRD;Type=Float" "GRD;Type=Colour" |
GPK Geopak grid file |
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No other qualifiers. |
GEOSOFT.INI section |
[DAT_GPK] BROWSE_IN="GPK" BROWSE_OUT="GPK" |
GXF Grid exchange file |
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COMP= |
compression level: -1 ASCII floating point (default) 0 ASCII integer |
DUMMY= |
Dummy value to use to represent dummy points in the grid. |
GEOSOFT.INI section |
[DAT_GXF] BROWSE_IN="GXF" BROWSE_OUT="GXF;COMP=-1" "GXF;COMP=0" "GXF;COMP=3" "GXF;COMP=4" "GXF;COMP=5" |
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