m.gc2ll

NAME

m.gc2ll - Converts geocentric to geographic coordinates.
(GRASS Data Import/Processing Program)

SYNOPSIS

m.gc2ll x=# y=# z=# s=spheroid

DESCRIPTION

m.gc2ll returns geographic coordinates for geocentric ones supplied by the user. It performs the reverse operation of the GRASS program m.ll2gc. The x, y and z values are the three dimensions needed to locate a point in three-dimensional space. The values that are printed include the latitude, the longitude and the height above (or distance below) the spheroid.

The list of spheroids available is somewhat dynamic. It may not contain exactly the ones listed below. To determine the current list of possible spheroids, simply type in:

m.gc2ll x=0 y=0 z=0 s=help

A list of available spheroids will be printed on the screen. If the spheroid desired is not on the list, the values for the semi-major axis and the eccentricity squared for the spheroid may be entered in place of a spheroid name in the following format:

s=a=semi-major_axis,e=eccentricity_squared

SOME POSSIBLE SPHEROIDS

(The on-line listing includes only the spheroid names)

Spheroid	Commonly used for:	Semi-major axis	Eccentricity sqrd
australian	Australia		6378160.0	0.0066945419
bessel		Japan			6377739.155	0.0066743722
clark66		N. America		6378206.4	0.006768658
clark80		France, Africa		6378249.145	0.0068035113
everest		India, Burma		6377276.345	0.0066378466
international	Europe			6378388.0	0.00672267
wgs72		worldwide coverage	6378135.0	0.006694317778

EXAMPLE

The command:: m.gc2ll x=0.0 y=0.0 z=6356750.520017 s=wgs72
Results:: lat=90N
lon=90W
h=0.0000

NOTES

For a brief discussion of spheroids see m.ll2u.

For a brief discussion of geocentric coordinates see m.ll2gc.

This is an experimental program. It is part of an initial effort to incorporate geographic coordinates into GRASS.

AUTHOR

Michael Shapiro, U.S.Army Construction Engineering Research Laboratory