1r.surf.area(1) Grass User's Manual r.surf.area(1)
2
3
4
6 r.surf.area - Surface area estimation for rasters.
7
9 raster
10
12 r.surf.area
13 r.surf.area help
14 r.surf.area input=string [vscale=float] [--verbose] [--quiet]
15
16 Parameters:
17 input=string
18 Raster file for surface
19
20 vscale=float
21 Vertical scale
22
24 r.surf.area Calculates area of regular 3D triangulated points (centers
25 of cells) in current region by adding areas of triangles. Therefore,
26 area of a flat surface will be reported as (rows + cols -1)*(area of
27 cell) less than area of flat region due to a half row and half column
28 missing around the perimeter.
29
31 This calculation is heavily dependent on data resolution (think of it
32 as a fractal shoreline problem, the more resolution the more detail,
33 the more area, etc). This program uses the CURRENT GRASS REGION, not
34 the resolution of the map. This is especially important for surfaces
35 with NULL values and highly irregular edges. The program does not
36 [currently] attempt to correct for the error introduced by this edge
37 effect.
38
39 This version actually calculates area twice for each triangle pair,
40 keeping a running minimum and maximum area depending on the direction
41 of the diagonal used.
42
43 Reported totals are: "Plan" area of NULL values within the current
44 GRASS region "Plan" area within calculation region (rows-1 * cols-1 *
45 cellarea) Average of the minimum and maximum calculated 3d triangle
46 area within this region "Plan" area within current GRASS region (rows *
47 cols * cellarea) Scaling of calculated area to current GRASS region
48 (see NOTE)
49
51 r.surf.area works best when the surface being evaluated extends to the
52 edges of the current GRASS region and the cell resolution is small.
53 Surfaces which are especially long and thin and have highly irregular
54 boudaries will tend to have underestimated surface areas. Setting a
55 high cell resolution (small area) will greatly reduce this impact, but
56 will cause longer processing times.
57
59 r.sum, r.surf.idw, r.surf.idw2, r.surf.fractal, r.surf.gauss, r.volume,
60 v.to.rast, r.slope.aspect, g.region
61
63 Bill Brown, USACERL December 21, 1994
64
65 Modified for floating point rasters and NULL values by Eric G. Miller
66 (October 17, 2000)
67
68 Last changed: $Date: 2007-05-29 13:42:23 +0200 (Tue, 29 May 2007) $
69
70 Full index
71
72 © 2003-2008 GRASS Development Team
73
74
75
76GRASS 6.3.0 r.surf.area(1)