[Proj] Grown error if re-projecting from 4269 to LCC (2285) and backward multiple times

vanadovv at hetnet.nl vanadovv at hetnet.nl
Fri Nov 3 06:25:16 EST 2017

I completely forgot about the LCCA projection, discussed some years ago.
But, LCCA is not LCCA.
The discussion around the PJ_lcca.c code seems to refer to the Lambert Conic Near-Conformal projection, fully documented in the EPSG Guidance Note 7-2.
This projection is also fully documented in the Libproj4 manual from Gerald Evenden, as the Lambert Conformal Conic Alternative Projection.
The code from Libproj is used in PROJ. The libproj/proj algorithms are completely different from the EPSG algorithms.
Eitherway: indeed, do not use this code for regular LCC projections!
 Oscar van Vlijmen
----Origineel Bericht----
Van : knudsen.thomas at gmail.com
Datum : 02/11/2017 22:55
Aan : proj at lists.maptools.org
Onderwerp : Re: [Proj] Grown error if re-projecting from 4269 to LCC (2285) and backward multiple times
  Hi Dmitry,
  I googled around for the “alternative” Lambert, without luck, but then this afternoon, I accidentally misspelled Lambert as “Lamber”, and ran into this thread: 
  http://lists.maptools.org/pipermail/proj/2003-March/000644.html where PROJ.4 founder Gerald Evenden, and long time PROJ.4 maintainer Frank Warmerdam discusses the LCCA, and Gerald mentions that it is a truncated series, only introduced to be compatible with some legacy French/North African systems, that were defined using the truncated series.
  Gerald explicitly states that it should not be used for new work, so my recommendation of looking at it was terribly bad advice. Also, I had not realized that LCCA does not support the secant (“2 parallel”) case, and hence lat_0 and not lat_1 & lat_2 are used for parameterizing the projection.
  So enough about LCCA - it should not be used for anything but to maintain interoperability with legacy reference systems.
[more: see original message]
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