Re: [Mapbuilder-proj] Bug or user error with lcc?

[Richard G. <ric...@gm...>]

The false easting (x_0) must always be in meters, even for coordinate
systems that are in feet.


On Tue, Jul 1, 2008 at 3:03 PM, David Zwarg <dz...@av...> wrote:
> Hello,
>
> I am using proj4js, and I am having difficulty getting good projection with
> a new projection definition.  It is entirely possible that I don't have the
> correct syntax for the definition file (or that I am totally missing
> something required), but it's giving results that are off by a factor of 3
> in 1 dimension (either X or Y, but not both).
>
> I am creating a definition for Pennsylvania State Plane, and this is the
> file EPSG2272.js:
>
> Proj4js.defs["EPSG:2272"] = "+proj=lcc \
> +lon_0=-77.75 \
> +lat_0=39.33333333333334 \
> +lat_1=39.9333333333333 \
> +lat_2=40.96666666666667 \
> +y_0=0.0 \
> +x_0=1968500.00 \
> +ellps=GRS80 \
> +datum=NAD83 \
> +nadgrids=@null +no_defs";
>
> I searched in http://www.epsg-registry.org/, and those are correct decimal
> degrees values.  I try to transform the location of Philadelphia, PA (
> -75.163808,39.951639 ), and I always get x:2189468, y:71889.  I am expecting
> something like x:2694800,y:236500.
>
> At first, I thought it was a ft/meter conversion, but when I add
> "+to_meter=0.3048006096012192" to the definition, the projected Y coordinate
> looks good, but the X coordinate is way off.
>
> Any help would be greatly appreciated,
> Thanks,
> David
>
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-- 
Richard Greenwood
ric...@gm...
www.greenwoodmap.com