Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro@zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: Algorithm for Latitude-Long
Message-ID: <C4HGHH.L8x@news.cecer.army.mil>
Sender: news@news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <199303231628.AA08469@murphy.gis.uiuc.edu>
Date: Fri, 26 Mar 1993 06:24:52 GMT
Lines: 19
In <199303231628.AA08469@murphy.gis.uiuc.edu> mountz@gis.uiuc.edu (Jacinda M. Barbehenn) writes:
I have a data set of the midpoints of counties based on latitude and
longitude coordinates. With this data set I want to create a matrix that
lists the distances between counties. However, to use latitude and longitude
data, I need an algorithm that will correct for the longitude distances.
Does anyone know of an algorithm that can do this?
If you can get a C programmer to help, there are C routines in the GRASS
libraries to compute distances between points in lat/lon which is
based on ellipsoidal geodesic formaulas for distance. The routines
are documented in the GRASS 4.0 programmer's manual. The r.buffer
program uses these routines as well as the d.meausre in 4.1beta.
--
Michael Shapiro U.S. Army CERL
Environmental Division