# [Proj] Geodesic software

Gerald I. Evenden geraldi.evenden at gmail.com
Sun Dec 7 16:18:33 EST 2008

```On my website

http://members.verizon.net/~gerald.evenden/proj4/

a library of converted NGS Vincenty geodesic procedure and an application
program, 'geodesic', are now available in geodesic20081207.tar.bz2.  In the
case of a spherical earth Snyder's preferred equations are used.

The only additional requirement is a libproj4.a library.

The program 'geodesic' has a fairly detailed help assistance and the user
should be successful without documentation.  Just start out with

geodesic
geod: earth ellps=WGS84 # set elliptical figure
geod: p1 20 30 # set base point in arc
geod: p2 30 45 # do an inverse projection
Point 1 Lon: 20dE  Lat: 30dN
Point 2 Lon: 30dE  Lat: 45dN
Azimuth p1->p2: 25d1'34.18757"
Distance: 1881597.763
Azimuth p2->p1: 211d10'34.37818"
geod: vector 100000 45 # do a forward projection
Point 1 Lon: 20dE  Lat: 30dN
Point 2 Lon: 20d44'15.34034"E  Lat: 30d38'8.82286"N
Azimuth p1->p2: 45d
Distance: 100000.000
Azimuth p2->p1: 225d22'20.44298"
geod: circle help # ask for help with arc generation
circle azimuth delta_azi

computes points along a circular arc centered at arc
structure node p1 and extending from arc node p2 in a
clockwise direction through an angle define by 'azimuth'
and divided by intermediate points at approximately 'az'
angular separation.
'circle 360 10' describes a circle of points at 10 degree
'delta_az' interval
geod: quit

That should give you an idea.

It is preliminary and any debug tries and suggestions would be appreciated.

All angular input are in the same format used by libproj4 and older pro4x
versions.
--
The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist
```