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. |
Related Topics
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