[OSRS-PROJ] Lambert Conformal Conic 1SP

[Frank Warmerdam]

Gerald I. Evenden wrote:
> 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.

Gerald,

Thanks for trying this out.  Seeing that you were getting the
correct results I was able to dig in deeper and figure out what
was happening differently.  It turns out that if proj finds the
proj_def.dat file, then it will pick up a default lat_2 value
of 45 from it, and this is what screws up the results.

The proj_def.dat file contains:

<lcc> # Conterminous U.S. map
lat_1=33
lat_2=45
<>

For my purposes it is sufficient to add the +no_defs item on
the commandline to supress the default values.

So in summary, for LCC1SP  use +lat_0 and +lat_1, and make sure that
the no_defs flag is used to avoid including any default parameters.

Best regards,

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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