DEM files are used for storing DEMs processed by WMS. After clipping, thinning, or smoothing an imported DEM you may wish to 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.
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DEM |
/* File type identifier */ |
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ORIGIN xlowerleft ylowerleft |
/* Southwest coordinare of DEM */ |
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DELTAX deltx |
/* X spacing of elevation points */ |
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DELTAY delty |
/* Y spacing of elevation points */ |
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ELEVATIONS ncol nrow |
/* Number of columns and rows in DEM */ |
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z11 |
/* elevation of row 1 column 1 */ |
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z21 |
/* elevation of row 2 column 1 */ |
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z31 |
/* elevation of row 3 column 1 */ |
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. |
|
|
. |
|
|
. |
|
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zncol,nrow |
/* elevation of row nrow column ncol */ |
Figure 1. DEM File Format.
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DEM |
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ORIGIN 1000.0 1500.0 |
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DELTAX 30.0 |
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DELTAY 30.0 |
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ELEVATIONS 450 300 |
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101 |
|
104 |
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. |
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. |
|
250 |
Figure 2. Sample DEM File.
The cards used in the DEM file are as follows:
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Card Type |
DEM |
|
Description |
File type identifier. Must be on first line of file. No fields. |
|
Required |
YES |
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Card Type |
ORDER |
||||||
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Description |
Defines the order in which elevations are read in. |
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Required |
NO (By default row major starting in upper left corner is assumed) |
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Format |
ORDER ordertype |
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Sample |
ORDER 0 |
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Field |
Variable |
Value |
Description | ||||
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1 |
xlowleft |
0-3 |
| ||||
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Card Type |
ORIGIN |
||
|
Description |
Defines the lower left (southwest) coordinates for the DEM. |
||
|
Required |
YES |
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|
Format |
ORIGIN xlowleft ylowleft |
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|
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 |
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|
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 |
delty |
+ |
Y spacing of DEM points. |
|
Card Type |
ELEVATIONS |
|||||||||
|
Description |
Elevations for the DEM. |
|||||||||
|
Required |
YES |
|||||||||
|
Format |
ELEVATIONS ncol nrow |
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|
Sample |
|
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|
Field |
Variable |
Value |
Description | |||||||
|
1 |
ncol |
+ |
Number of columns. | |||||||
|
2 |
nrow |
+ |
Number of rows. | |||||||
|
3-n |
z |
+ |
Elevations of DEM points. | |||||||