[Proj] Proj4js EPSG:4326 to EPSG:26786 (SP NAD27) 100+ feet Off

[Frank Warmerdam]

On Fri, Oct 14, 2011 at 7:38 PM, Scott DeHainaut
<scottdehainaut at comcast.net> wrote:
> Greetings,
>
> I'm working on a web project and using Proj4js for the first time to project
> coordinates from Google Maps lat/lon WGS84 into Massachusetts Stateplane
> NAD27 feet.  To test my process I'm using a surveyed point for which I have
> both lat/lon and MA SP NAD27 feet coordinates.  The surveyed coordinates in
> SP are easting 866074.86 and northing 231916.59.
>
> When I use Proj4js to go from lat/lon to MA SP NAD27, I'm 100+ feet from the
> surveyed coordinates.  Here's the javascript snippet that's performing the
> conversion:
>
> var latGeo = 41.63238400230
> var lonGeo = -70.52620887720
> var source = new Proj4js.Proj('EPSG:4326');  /* Lat/Lon projection */
> var dest = new Proj4js.Proj('EPSG:26786');  /* MA SP Mainland NAD27
> projection */

Scott,

I do not think that Proj4JS does datum shifts that
involve grid shift files (like NAD27 to WGS84).

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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