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Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro at zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: Algorithm for Latitude-Long
Message-ID: <C4HGHH.L8x at news.cecer.army.mil>
Sender: news at news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <199303231628.AA08469 at murphy.gis.uiuc.edu>
Date: Fri, 26 Mar 1993 06:24:52 GMT
Lines: 19

In <199303231628.AA08469 at murphy.gis.uiuc.edu> mountz at 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