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Posted by Paul Cooper on February 27, 2008, 5:01 am
Please log in for more thread options On Tue, 26 Feb 2008 19:10:30 -0800 (PST), user923005
>> I am working on implementing the formulae for Transverse Mercator in a
>> Java Map Projection Package. I have implemented the formulae given on
>> pp 60- 64 of Snyder (1987) , Map Projections - A Working Manual.
>> However, these are not accurate beyond 5-10 degrees from the central
>> meridian. I have also found the paper referenced by Snyder as "Army,
>> 1962" that gives more terms for the equations; I haven't tried it yet
>> but it only claims accuracy to 24 degrees.
>>
>> However, both these document only Taylor expansions of the original
>> unclosed equations, and do not give the "open" forms of the equations,
>> stating that they are of little practical use because they converge
>> too slowly.
>>
>> These days, I wonder if this is true! Processing power is far greater
>> than it was in 1987, and I would like to have a go at implementing an
>> iterative solution using the basic "open" form of the equations, in
>> the same manner as I usually do for other projections. Here we hit a
>> snag, though - I don't have a reference for them; everyone seems just
>> to give series based solutions. Can someone point me in the right
>> direction?
>>
>> It seems to me that as long as I have a form that converges, it is
>> unlikely that it would be so slow as to be unuseable in the
>> environment I am working in, and it would be far more accurate.
>
>Maybe this is helpful:
>http://www.dwaf.gov.za/IWQS/gauss/gauss.html
Thanks, I'd already found that one. It still uses Taylor expansions,
but I haven't looked at it in detail. It is a shame it is published in
HTML so it is difficult to print it all out!
Paul
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