# [OSRS-PROJ] Using PROJ for location estimation in wireless environment

Ed McNierney ed at topozone.com
Fri May 30 17:43:51 EDT 2003

```Robert -

As a starting point, I'd suggest using a Transverse Mercator projection,
which will give you planar Northing and Easting coordinates (usually in
meters) - similar to the common UTM projection.  You can minimize
distortion by setting the central meridian of the projection to the
average of the three longitudes of your F1, F2, F3 points.

This will give you X and Y coordinates in meters of F1, F2, and F3, and
then it's just a little algebra find the point where D1, D2, and D3
indicate.

If you customize the central meridian to your points, and those points
are not too near the poles, and the points are indeed only 30 miles
apart or less, then I'd expect you would get a rather good result
("rather good", of course, simply being my subjective estimate without
knowing what kind of accuracy you need in your results).

Does that sound like a reasonable start?

- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: (978) 251-4242  Fax: (978) 251-1396
ed at topozone.com

-----Original Message-----
From: Saxon Robert-QA2183 [mailto:Robert.Saxon at motorola.com]
Sent: Friday, May 30, 2003 4:48 PM
To: 'osrs-proj at remotesensing.org'
Subject: [OSRS-PROJ] Using PROJ for location estimation in wireless
environment

I am looking for a second method to use for location estimation.
I am working with a communication system that can provide some
estimation on distance. The setup is as follows:

- I have 3 or more fixed positions in Lat/Long (GPS).
Maximum distance between each point is under 30 miles.

- I have a relative distance between my target location
and each fixed point.

- Goal is to provide estimate of Lat/Long of the target based
on the fixed locations and the relative distance.

I have the following information:

1. Lat/Long of fixed point F1.
2. Distance in meter from target to F1.
3. Lat/Long of fixed point F2.
4. Distance in meter from target to F2.
5. Lat/Long of fixed point F3.
6. Distance in meter from target to F3

I am look for ideas on how to use "proj" software to guest-to-mate
the Lat/Long of my target location. I have software that does this
but want a "second opinion". Can I use "proj" commands to accomplish
this goal?

Robert A. Saxon
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```