| [Visitor (120.204.*.*)]answers [Chinese ] | Time :2021-07-26 |  Grid data characteristics
Point entities are represented by a grid cell;
Line entities are represented by adjacent grid cells connected in a certain direction in a string;
A polygon body (area) is represented by a collection of blocks of adjacent raster cells with the same properties.
Features of the grid structure
The data records the pointer or the property itself directly, and its location is given according to the row number converted to the appropriate coordinates. That is, the positioning is based on the location of the data in the data collection.
As shown in Figure 3.1 (a), data 1 represents a point in the property or number bit, which is obtained by the third row and column 5. Because the grid structure is arranged according to certain rules, the represented entity location is easily hidden in the storage structure of the grid file. Each code itself in a grid file explicitly represents the property or property encoding of an entity, which, if encoded as a property, can serve as a pointer to the entity property sheet. Figure 3.1 (a) represents entities with codes 1, 3, 6, Figure 3.1 (b) represents a line entity with code 8, and Figure 3.1 (c) represents face entities with codes of 4,7,9.
(a) Point (b) line (c) area
0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 0 4 4 4 4 7 7 7 7
0 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 4 4 4 4 4 7 7 7
0 0 0 0 1 0 0 0 0 0 0 0 8 0 0 0 4 4 4 4 9 9 7 7
0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 4 9 9 9 7 7
0 0 0 3 0 0 0 0 0 0 0 0 0 8 0 0 0 0 0 9 9 9 7 7
0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 0 9 9 9 9 9
0 0 0 0 0 6 0 0 0 0 0 8 8 0 0 0 0 0 0 0 9 9 9 9
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 9 9 |
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