1r.surf.area(1) Grass User's Manual r.surf.area(1)
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6 r.surf.area - Prints estimation of surface area for raster map.
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9 raster, surface, statistics, area estimation
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12 r.surf.area
13 r.surf.area --help
14 r.surf.area map=name [vscale=float] [units=string] [--help]
15 [--verbose] [--quiet] [--ui]
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17 Flags:
18 --help
19 Print usage summary
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21 --verbose
22 Verbose module output
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24 --quiet
25 Quiet module output
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27 --ui
28 Force launching GUI dialog
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30 Parameters:
31 map=name [required]
32 Name of raster map
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34 vscale=float
35 Vertical scale
36 Default: 1.0
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38 units=string
39 Output units
40 Default: square map units
41 Options: miles, feet, meters, kilometers, acres, hectares
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44 r.surf.area calculates area of regular 3D triangulated points (centers
45 of cells) in current region by adding areas of triangles. Therefore,
46 area of a flat surface will be reported as (rows + cols -1) * (area of
47 cell) less than area of flat region due to a half row and half column
48 missing around the perimeter.
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51 This calculation is heavily dependent on data resolution (think of it
52 as a fractal shoreline problem, the more resolution the more detail,
53 the more area, etc). This module uses the current region settings, not
54 the resolution of the raster map. This is especially important for sur‐
55 faces with NULL values and highly irregular edges. The module does not
56 [currently] attempt to correct for the error introduced by this edge
57 effect.
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59 This version actually calculates area twice for each triangle pair,
60 keeping a running minimum and maximum area depending on the direction
61 of the diagonal used.
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63 Reported totals are:
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65 1 "Plan" area of NULL values within the current GRASS region
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67 2 "Plan" area within calculation region (rows-1 * cols-1 * cel‐
68 larea)
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70 3 Average of the minimum and maximum calculated 3d triangle area
71 within this region
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73 4 "Plan" area within current computational region (rows * cols *
74 cellarea)
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76 5 Scaling of calculated area to current region
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78 r.surf.area works best when the surface being evaluated extends to the
79 edges of the current region and the cell resolution is small. Surfaces
80 which are especially long and thin and have highly irregular boundaries
81 will tend to have underestimated surface areas. Setting a high cell
82 resolution (small area) will greatly reduce this impact, but will cause
83 longer processing times.
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86 g.region -p raster=elevation
87 r.surf.area map=elevation units=hectares
88 Null value area ignored in calculation: 0.000000
89 Plan area used in calculation: 20221.510000
90 Surface area calculation(low, high, avg):
91 20294.310421 20320.936368 20307.623395
92 Current region plan area: 20250.000000
93 Estimated region Surface Area: 20336.234719
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96 g.region, r.surf.idw, r.surf.fractal, r.surf.gauss, r.volume,
97 r.slope.aspect, v.to.rast
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100 Bill Brown, USACERL December 21, 1994
101 Modified for floating point rasters and NULL values by Eric G. Miller
102 (October 17, 2000)
103 Updated for GRASS 7, and units option by Martin Landa, Czech Technical
104 University in Prague, Czech Republic (October 2011)
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106 Last changed: $Date: 2016-09-19 11:37:30 +0200 (Mon, 19 Sep 2016) $
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109 Available at: r.surf.area source code (history)
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111 Main index | Raster index | Topics index | Keywords index | Graphical
112 index | Full index
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114 © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
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118GRASS 7.4.4 r.surf.area(1)