WMS:DEM Files

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DEM files are used for storing DEMs processed by WMS. After clipping, thinning, or smoothing an imported DEM, save it to a WMS formatted file so that it can be recalled later without having to perform the same processing steps. The DEM file format is shown in Figure 1 and a sample file is shown in Figure 2.


DEM /* File type identifier */
ORIGIN xlowerleft ylowerleft /* Southwest coordinare of DEM */
DELTAX deltx /* X spacing of elevation points */
DELTAY delty /* Y spacing of elevation points */
ELEVATIONS ncol nrow /* Number of columns and rows in DEM */
z11 /* elevation of row 1 column 1 */
z21 /* elevation of row 2 column 1 */
z31 /* elevation of row 3 column 1 */
.
.
.
zncol,nrow /* elevation of row nrow column ncol */

Figure 1. DEM File Format.


DEM
ORIGIN 1000.0 1500.0
DELTAX 30.0
DELTAY 30.0
ELEVATIONS 450 300
101
104
.
.
250

Figure 2. Sample DEM File.


The cards used in the DEM file are as follows:

Card Type DEM
Description File type identifier. Must be on first line of file. No fields.
Required YES


Card Type ORDER
Description Defines the order in which elevations are read in.
Required NO (By default row major starting in upper left corner is assumed)
Format ORDER ordertype
Sample ORDER 0
Field Variable Value Description
1 xlowleft 0-3 0 - Elevations start at upper left, one row at a time.
1 - Elevations start at upper left, one col. at a time.
2 - Elevations start at lower left, one row at a time.
3 - Elevations start at lower left, one col. at a time.


Card Type ORIGIN
Description Defines the lower left (southwest) coordinates for the DEM.
Required YES
Format ORIGIN xlowleft ylowleft
Sample TNAM 1000.0 1500.0
Field Variable Value Description
1 xlowleft ± Lower left X coordinate of the DEM
2 ylowleft ± Lower left Y coordinate of the DEM


Card Type DELTAX
Description The X spacing between DEM points.
Required YES
Format DELTAX deltx
Sample DELTAX 30.0
Field Variable Value Description
1 deltx + X spacing of DEM points.


Card Type DELTAY
Description The Y spacing between DEM points.
Required YES
Format DELTAY delty
Sample DELTAY 30.0
Field Variable Value Description
1 deltx + Y spacing of DEM points.


Card Type ELEVATIONS
Description Elevations for the DEM.
Required YES
Format ELEVATIONS ncol nrow
Sample ELEVATIONS 450 300
101
104
.
.
.
98
Field Variable Value Description
1 ncol + Number of columns.
2 nrow + Number of rows.
3-n z + Elevations of DEM points.

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