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NAME

v.in.geodesic

DESCRIPTION

v.in.geodesic creates a new vector map containing a great circle line. The user can select to use either a starting and ending point, or a starting point with initial azimuth and line length.

The initial azimuth is measured in degrees clockwise from north. Line length and segment distance are both measured in meters.

If the distance parameter is given, polyline segments will be broken at that distance interval. Otherwise the line will be broken into nsteps equally spaced segments.

NOTES

Currently this module only works from a Lat/Long location. Use v.proj to reproject the results if needed.

This module requires the geod program from PROJ.4 to be installed. (often this is already installed with the GRASS package)

EXAMPLES

Create a geodesic line between two points: 
start_lat=-49
start_lon=125
end_lat=-32
end_lon=180

v.in.geodesic map=geodesic_line coor="$start_lon,$start_lat,$end_lon,$end_lat"
Create a geodesic line from a starting point, initial azimuth of ENE (67.5 deg), and 500 km long: 
start_lat=-40.5
start_lon=172.5
azimuth=67.5
length=500000

v.in.geodesic map=geodesic_line line="$start_lon,$start_lat,$azimuth,$length"

SEE ALSO

d.geodesic
d.rhumbline
m.cogo
r.profile
r.transect

AUTHOR

Hamish Bowman
Dept. Marine Science
University of Otago
Dunedin, New Zealand

Last changed: $Date: 2011-11-08 13:56:45 -0800 (Tue, 08 Nov 2011) $

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