[OSRS-PROJ] Lambert Conformal Conic 1SP

[Gerald I. Evenden]

I compiled and loaded PROJ on my RedHat Linux system, edited your
email into a script and executed it:

proj +proj=lcc +lat_1=18 +lat_0=18 +lon_0=-77 +k_0=1 +x_0=250000
+y_0=150000 +ellps=clrk66 +units=m <<EOF
76d56'37.26"W 17d55'55.80"N
EOF

produces:

255966.58       142493.51

These numbers seem to match the JAD69 / Jamaica National Grid
numbers in the referred to web page.

You seem to have a flawed version of proj.

However, I do agree that there should be a set of standards
which can be used to test installations of any cartographic
projection system.  I do have a set of numbers which I got
from NMD which can be used to verify SPCS conversions.  But
material for foreign systems is lacking in my shop.

On Sat, 2003-02-08 at 14:32, Frank Warmerdam wrote:
> Folks,
> 
> I have found what I believe to be an inaccuracy in the LCC 1SP support in
> PROJ.4, and I wonder if anyone has any comment on possible solutions.
> 
> As an example, using this commandline:
> 
> proj +proj=lcc +lat_1=18 +lat_0=18 +lon_0=-77 +k_0=1 +x_0=250000 +y_0=150000 
> +ellps=clrk66 +units=m
> 
> And input:
> 
> 76d56'37.26"W 17d55'55.80"N
> 
> I get this output:
> 
> 255968.19       142493.14
> 
> The coordinate system is EPSG 24200 - JAD69 / Jamaica National Grid and is
> used as an example in the EPSG paper "Guidance note #7" available at:
> 
>    http://www.remotesensing.org/geotiff/proj_list/guid7.html
> 
> or the section on LCC 1SP excerped at:
>    http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_1sp.html
> 
> Looking there we see the result should be (255966.58, 142493.51).  The error
> is a couple of meters.  Not outragous, but significant, and plenty to trip
> up my autotests.
> 
> I have run the same coordinate system through the FME software (based on the
> projections engine from Mentor Software and it matches the EPSG results to
> a centimeter or better.
> 
> Is it possible the problem is with using a general LCC formula for the 1SP
> case when there is a more precise way of handling that?
> 
> By the way, this has come up as I am refining support in FME for coordinate
> systems derived from EPSG.  As part of this effort I have produced a test
> file of reference points for every projected coordinate system and the expected
> result when reprojected into lat/long.  I generated the test file using PROJ.4
> (bound within OGR) and then run it again using the FME projections engine.
> 
> It is my thought that such a test suite of known points could be useful for
> validating other projection engines as well ... with the caveat of course that
> PROJ.4 isn't "the master", but if differences are found it suggests the
> need for further manual examination.
> 
> Best regards, ...

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