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

[Christopher Barker]

Roger Oberholtzer wrote:
>> First, interpolating positions from easting/northing values is shaky and 
>> accuracy of such efforts is highly dependent upon the distance between points 
>> used in the operation.

My first thought is -- why so this in projected space? It sounds like 
you have lat-long, and you want to interpolate between two points, and 
get back lat/long again. So could you do this in lat-long space?

To answer that, we need to know what you mean by interpolate?

Do you have two points and want to know what the midpoint is, for 
example? If so, what does "mid point" mean? That's not obvious on a 
globe, which may be why you're using projected coordinates, but with 
Gerald's recently released geodetic (geodesic?) tools, it should be 
doable to find a point along a great circle connecting two points, for 
instance.

> The distance is in the order of meters. Typically less than 10.

In that case, you can probably get pretty darn close by pretending that 
that lat-long units are Cartesian -- and that would be really easy! How 
accurate do you really need to be?

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer

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