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GRASS Programmer's Manual
6.5.svn(2014)-r66266
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GIS Library - Ellipse area routines. More...

Go to the source code of this file.
Functions | |
| int | G_begin_zone_area_on_ellipsoid (double a, double e2, double s) |
| Begin area calculations for ellipsoid. More... | |
| double | G_darea0_on_ellipsoid (double lat) |
| Calculate integral for area between two latitudes. More... | |
| double | G_area_for_zone_on_ellipsoid (double north, double south) |
| Calculates area between latitudes. More... | |
GIS Library - Ellipse area routines.
(C) 2001-2008 by the GRASS Development Team
This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.
Definition in file area_ellipse.c.
| double G_area_for_zone_on_ellipsoid | ( | double | north, |
| double | south | ||
| ) |
Calculates area between latitudes.
This routine shows how to calculate area between two lats, but isn't efficient for row by row since G_darea0_on_ellipsoid() will be called twice for the same lat, once as a south then again as a north.
Returns the area between latitudes north and south scaled by the factor s passed to G_begin_zone_area_on_ellipsoid().
| [in] | north | |
| [in] | south |
Definition at line 96 of file area_ellipse.c.
References G_darea0_on_ellipsoid().
| int G_begin_zone_area_on_ellipsoid | ( | double | a, |
| double | e2, | ||
| double | s | ||
| ) |
Begin area calculations for ellipsoid.
Initializes raster area calculations for an ellipsoid, where a is the semi-major axis of the ellipse (in meters), e2 is the ellipsoid eccentricity squared, and s is a scale factor to allow for calculations of part of the zone (s=1.0 is full zone, s=0.5 is half the zone, and s=360/ew_res is for a single grid cell).
Note: e2 must be positive. A negative value makes no sense, and zero implies a sphere.
| [in] | a | semi-major axis |
| [in] | e2 | ellipsoid eccentricity |
| [in] | s | scale factor |
Definition at line 50 of file area_ellipse.c.
Referenced by G_begin_cell_area_calculations().
| double G_darea0_on_ellipsoid | ( | double | lat | ) |
Calculate integral for area between two latitudes.
This routine is part of the integral for the area between two latitudes.
| [in] | lat |
Definition at line 69 of file area_ellipse.c.
References wxnviz::log, and Radians.
Referenced by G_area_for_zone_on_ellipsoid(), and G_begin_cell_area_calculations().