In the DSS file, grid parameter values are stored in a single array, starting with the value in the minimum-x, minimum-y (or lower left) cell in the two-dimensional array. The values proceed by row in increasing column numbers and increasing row numbers, as illustrated below:
|
|
|
|
|
| 7 | 8 | 9 |
|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| 4 | 5 | 6 |
Array | 1 | 2 | 3 |
| Grid |
The array of parameter values is always compressed before it is written to a DSS file. Two compression methods are used. One is a run-length encoding method, which replaces repeated zero and null values with the number of times zero or null was repeated. The second method is the deflate method, which is included in the zlib library described in RFC 1950. The deflate format itself is described in RFC 1951.