[Proj] lat/long to northing/easting and back again

Christopher Barker Chris.Barker at noaa.gov
Tue Mar 17 11:16:57 EST 2009

Roger Oberholtzer wrote:
> We need to involve the odd gyroscope, inclinometer, and pulse distance
> transducer at this point. All are calculating distances in meters.

going lat-long to meters isn't so hard -- in fact, if I'm right about 
geodesics (geodetics?) that's exactly what you can do:

start at point A, and go X meters at a given bearing, and it tells you 
where are you are in lat-long.

> Our data is tagged with time that has been synchronized with our GPS.
> When we want to know where we are, we start by determining when we were
> at the point we want to know the location of.

you should be able to do this in lat-long too.

I guess my thought is that if you have a bunch of data in a given 
projects, then by all means use it. But if you are only going through a 
projection to do geometric calculations, then going back to lat-long, 
you may well be better off staying in lat-long.

> The distances are luckily too small to have to involve the great circle.

Then it really doesn't matter much how you do it! -- you could probably 
stick to spherical geometry, or even straight Cartesian in lat-long and 
be fine.


Christopher Barker, Ph.D.

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
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Chris.Barker at noaa.gov

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