[Proj] Info on proj4 formulas

Antti Castrén antti.castren at iki.fi
Fri May 9 12:36:03 EST 2014


It seems that they differ at least on Transverse Mercator. OGP
Guidance currently recommends so called JHS formulas which are
satisfactory within +/-40 degrees from central meridian compared to
Snyder's +/-4 degrees. Snyder's formulas seem to be coded in proj.4
PJ_tmerc if I have read the current version correctly.

For more information read OGP document pages 48...53



FYI: The so called JHS formulas were actually created by prof R A
Hirvonen and published (in Finnish) already back in 1972.

2014-05-09 17:31 GMT+03:00 Nick Ves <vesnikos at gmail.com>:
> Intresting,
> But now I'm wondering if the OGP's "Geomatics Guidance Note Number 7,
> part 2 Coordinate Conversions and Transformations including Formulas"
> [0] has been taken into account in the realizations of the formulas.
> [0] http://www.ogp.org.uk/pubs/373-07-2.pdf
> On Fri, May 9, 2014 at 5:19 PM, Norman Vine <nhv at cape.com> wrote:
>> On May 9, 2014, at 10:05 AM, Andrea Peri <aperi2007 at gmail.com> wrote:
>> Hi,
>> You have right.
>> I can read and try to understand the code but i don't know the PROJ lib.
>> There is a specific file source dedicate to the reprojection functions ?
>> Each projection has its own file these are named  "PJ_XXXX"
>> where XXXX is an abbreviation of the projection's name
>> Proj4 is the codification of Snyder's "Map Projections: A Working Manual"
>> Where the derivation of the projections are discussed
>> this is available as a pdf from
>> http://pubs.er.usgs.gov/publication/pp1395
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