DEMWRIT -- Write DEM to Text File

Writes 16-bit elevation data from a PCIDSK database file to one or more USGS (United States Geological Survey) DEM (Digital Elevation Model) format files. DEMWRIT writes only ASCII format 7.5-minute (30 m. resolution, 1:24,000 scale) DEM data, NOT "binary" (unformatted), or 1-degree DEM data.

Progress of this program can be monitored. See MONITOR section.

See Also: MIDEM, MIDTED, GDB

PARAMETERS

DEMWRIT is controlled by the following global parameters: 

Name     Prompt                                  Count     Type
FILI     Database Input File Name                1-64      Char
FILO     Database Output File Name               1-64      Char
DBIC     Database Input Channel List             1         Int
DBIW     Database Input Window                   0-4       Int

FILI

Specifies the file name of the input PCIDSK image file containing the DEM data to be written. The PCIDSK file must be georeferenced using UTM coordinates WITH A ZONE NUMBER. 

 EASI>FILI="filespec"

FILO

Specifies the file name (without extension) of the DEM file(s) to be created. The DEM file(s) will be created automatically. Please specify a filename.

More than one DEM file may be written, depending on the size and location of the DEM data. The DEM files are created and ordered from right to left (west to east), and from top to bottom (north to south). Each DEM file covers a 7.5 by 7.5 minute area. The DEM file names are of the form "filename.m-n", where "m" and "n" specify the row and column number. 

 EASI>FILO="filename"
Note: on some systems, where file extensions can only be three characters, the generated names may be slightly different than described above. Using a short file name (4 characters or less) is recommended on OS/2 and Windows systems.

DBIC

Specifies the input image channel from which to read the DEM data. The input channel can be any type. However, DEM data are always output as signed 16-bit values. 

 EASI>DBIC=i

DBIW

Specifies the input window of DEM data from the PCIDSK file to be written to DEM files. 

 EASI>DBIW=Xoffset,Yoffset,Xsize,Ysize
 EASI>DBIW=                             | use entire image

DETAILS

DEMWRIT writes ASCII format 7.5-minute (30 m resolution, 1:24,000 scale) DEM data, but NOT "binary" (unformatted) 1-degree or 7.5-minute DEM data. DEMWRIT only creates DEM files with four corners.

DEMWRIT transfers image data on an image channel (DBIC) to a USGS (United States Geological Survey) DEM (Digital Elevation Model) format text file on disk. The PCIDSK file must be georeferenced using UTM coordinates WITH A ZONE NUMBER (using the GEOSET or PROSET programs).

DEM files are created and ordered from right to left (west to east) and from top to bottom (north to south). Each DEM file covers a 7.5 minute longitude by 7.5 minute latitude area. The file extension for the DEM file specifies its location within the grid of new DEM files created by DEMWRIT as follows: 

 +-------------------------------+
 |  1-1  |  1-2  |  ...  |  1-n  |
 +-------------------------------+
 |  2-1  |  2-2  |  ...  |  2-n  |
 +-------------------------------+
 |  ...  |  ...  |  ...  |  ...  |
 +-------------------------------+
 |  m-1  |  m-2  |  ...  |  m-n  |
 +-------------------------------+
The grid of DEM files may not be perfectly rectangular. Some files along the first or last row or column may be missing, depending on the location of the input window from the PCIDSK image file. Portions of the DEM file which do not cover the area specified by the input window have zero filler.

MONITOR

Program progress can be monitored by printing the percentage of completed processing in odometer fashion. A system parameter, MONITOR, controls this activity: 

 EASI>MONITOR="ON"           | turn monitor ON  (default)
 EASI>MONITOR="OFF"          | turn monitor OFF (recommended if
                             | running in batch/background mode)

EXAMPLE

Write a DEM file for the 16-bit signed elevation data stored on channel 10 of the irvine.pix PCIDSK file. The result is six DEM files (two rows and three columns) which cover the area between 117.875W and 117.5W degrees longitude, and between 33.75N and 33.5N degrees latitude. The output files are called irvine.1-1, irvine.1-2, irvine.1-3, irvine.2-1, irvine.2-2, and irvine.2-3. 

 EASI>FILI="irvine.pix"
 EASI>FILO="irvine"
 EASI>DBIC=10
 EASI>DBIW=
 EASI>RUN DEMWRIT
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