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)

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

Continuous function data (default), displays smoothly

PIXEL=1

Pixel data, displays as grid cells.

GEOSOFT.INI section

[DAT_ARC]
BROWSE_IN="ARC"
BROWSE_OUT="ARC"

ERM Earth Resource Mapper

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]
BROWSE_IN="ERM"
BROWSE_OUT="ERM"

GRD Geosoft grid file

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:

 

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.
Default is DUMMY=255,255,255 (white).
To disable dummy colour, enter "DUMMY=".

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
Bits Figures
4 1
7 2
10 3
14 4
17 5
20 6
23 almost 7 (this is the maximum)

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

 

No other qualifiers.

GEOSOFT.INI section

[DAT_GPK]

BROWSE_IN="GPK"

BROWSE_OUT="GPK"

GXF Grid exchange file

COMP=

compression level: -1 ASCII floating point (default)

0 ASCII integer
1 4 -bit data
2 8 -bit data
3 16 -bit data
4 32 -bit data
5 all data precision

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"

IMG Image format files (BMP,PCX,JPG,TIF,EPS,GIF,TGA etc...)

BAND=R

Red band only

BAND=G

Green band only

BAND=B

Yellow band only

BRT=

Brightness, 0 -> 2.0 (black -> white), default is BRT=1.0

PAGE=

Page number from a multi-page image

SMOOTH=

0 - not smoothed, 1 - smoothed (default)

DUMMY=

r,g,b Dummy colour. Default is DUMMY=255,255,255 (white) To disable dummy colour, enter "DUMMY="

T=

Image type: T=1 Bitmap
T=2 GeoTiffBitmap
T=3 GIFGeoTiff
T=4 IMG
T=5 JPEG
T=6 PCX
T=7 Targa
T=8 Tiff

 

GEOTIFF files are supported, but you should use the TIF DAT for GeoTIF files.

If an ArcInfo world file (*.*w or .wld) is found in the same directory as the image file, the coordinate registration is read from that file.

Coordinate registration can also be entered into an INI file with the same name as the image, but extension "ini". The INI parameters are:

Image_Dat.X_Seperation=
Image_Dat.Y_Seperation=
Image_Dat.X_Origin=
Image_Dat.Y_Origin=
Image_Dat.Rotation

GEOSOFT.INI section

[DAT_IMG]

BROWSE_IN="IMG;T=1" Bitmap
"IMG;T=2" GeoTiff
"IMG;T=3" GIF
"IMG;T=4" IMG
"IMG;T=5" JPEG
"IMG;T=6" PCX
"IMG;T=7" Targa
"IMG;T=8" Tiff

SRF Surfer grids

 

no parameters

GEOSOFT.INI section

[DAT_SRF]

BROWSE_IN="SRF"

BROWSE_OUT="SRF"

TIF GeoTIF images

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.

GEO=

0 - Standard TIFF

1 - GeoTIFF (default)

TYPE=

DATA - if set, data is stored in the GeoTIF rather than colour.

COMP=

NONE - Uncompressed

PACKBITS - Packbits compression

LZW - LZW compression

This DAT can read LZW compressed grids, but it cannot write LZW compressed grids due to LZW license restrictions.

BRT=

Brightness, 0 -> 2.0 (black -> white), default is BRT=1.0

DUMMY=

r,g,b Dummy colour. Default is DUMMY=255,255,255 (white). To disable dummy colour, enter "DUMMY=".

GEOSOFT.INI section

[DAT_TIF]

BROWSE_IN="TIF"

BROWSE_OUT="TIF"

USG USGS grids

DUMMY=

Dummy value to use to represent dummy points in the grid.

GEOSOFT.INI section

[DAT_USG]

BROWSE_IN="USG"

BROWSE_OUT="USG"

SAT Binary satellite data (BIP, BIL, BSQ)

 

Files of this type generally have a data file (with no extension) and an accompanying header file. Normally, you will choose the header file and the data file is assumed to have the same name without the extension. If the data file has a different name, you can use DATA= to specify the data file.

T=

Binary file type:

T=0 BIL with INI header (*.ini) (see below for INI doc)

T=1 EOSAT Fast Format (*.*)

T=2 EOSAT MSS (old 4 band BIL) (*.*)

T=3 Landsat MSS (4 band BSQ) (*.*)

T=4 BIL with *.hdr header (*.*)

T=5 ETOPO5 5' DEM (etopo5.*)

T=6 GTOPO30 30\" DEM (*.dem) and GLOBE 30\"DEM (*10*.)

T=7 SRTM DTED

DATA=

to specify the name of the data file if it is not the same as the header file without the extension.

The following is an example of an INI header file

[Sat_Dat]
COLUMNS=100 / Mandatory
LINES=100 / Mandatory
DATATYPE=IEEE4ByteReal / Mandatory
/ one of:
/ Unsigned8BitInteger
/ Signed8BitInteger
/ Unsigned16BitInteger
/ Signed16BitInteger
/ Unsigned32BitInteger
/ Signed32BitInteger
/ IEEE4ByteReal
/ IEEE8ByteReal
/
BANDS=1 / Number of bands
HEADERSIZE=0 /
BANDLAYOUT=BIL / BIP, BIL, or BSQ
BYTEORDER=LSBFirst / LSBFirst (Intel) or MSBFirst (Motorola)
X_ORIGIN=0.0 /
Y_ORIGIN=0.0 /
X_SEPARATION=1.0 /
Y_SEPARATION=1.0 /
ROTATION=0.0 /
DUMMY=-1E+32 / dummy value
KX=1 / 1 for bottom left origin
/ -2 for upper left origin
/ POSC Coordinate System:
CS_Name / name as "datum / transform"
CS_Datum / datum_name[,major_axis,eccentricity,pm]
CS_Projection / method,parameter1,parameter2,...
CS_Units / unit_abbr,m/units
CS_Locdatum" / local_datun,dx,dy,dz,rx,ry,rz,scale

 

DEM USGS Digital Elevation Models

 

This DAT id used for reading (not writing) USGS DEM (Digital Elevation Model) files.
The "DATUM" decoration comes into play only in "old" format files, where fields 16-29 are left blank. (Fields 16-29 provide the full datum definition in newer format DEM files). If these fields are defined, then this decoration is ignored.

DATUM=0

(default) Use NAD27 datum if elements 16-29 are blank (old format) All USGS DEMs lacking elements 16-29.

DATUM=1

Use WGS 72 datum. (All NIMA and DTED DEMs where fields 16-29 are blank)

SDT USGS SDT S (Spatial Data Transfer Standard Mapping) DEM grids

DUMMY

Dummy value used in the SDTS grid. By default this is 32767, but we have seen an instance where it was -14593.

The SDTS standard also uses a fill value to pad grids to a rectangle. This value is -32766, and is also replaced with dummies on the import.