[MetaCRS] Problems when reprojecting with Proj4js

[Michael Adair]

Hugo,

I just tried your test case in the index page of Proj4js trunk and it 
came up with the correct transformed coords.  Do you have an up-to-date 
version of Proj4js?

Mike

On 04/03/2011 9:21 AM, Hugo wrote:
> Hello all,
>
> I'm developing an application using GeoExt and Openlayers. I'm 
> implementing a widget that will allow the user to enter coordinates in 
> several SRS and the map gets zoomed to it while, at the same time, a 
> vector feature is added to a specific layer. However i'm getting 
> strange values after reprojecting the coordinates. I really need to 
> use proj4js because some of the epsg definitions for Portuguese SRS do 
> not have the local transformation parameters. For example, i wish to 
> reproject from EPSG:20791 to EPSG:900913. This is what i have done:
>
> 1. Included proj4js-combined.js in the web page
>
> 2. Created the SRS defintions:
> Proj4js.defs["EPSG:20791"] = "+proj=tmerc +lat_0=39.66666666666666 
> +lon_0=1 +k=1 +x_0=0 +y_0=0 +ellps=intl +pm=lisbon +units=m 
> +towgs84=-288.885,-91.744,+126.244,-1.691,0.410,-0.211,-4.598";
>
> Proj4js.defs["EPSG:900913"] = "+proj=merc +a=6378137 +b=6378137 
> +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null 
> +no_defs";
>
> 3. Then i tried the following:
>
> var mercator = new OpenLayers.Projection("EPSG:900913");
> var hglipcc = new OpenLayers.Projection("EPSG:20791");
> xcoord = 19120.326567
> ycoord = -293121.903092
> var coordMarker = new OpenLayers.Geometry.Point(xcoord, ycoord);
> var coordMarkerRep = coordMarker.transform (hglipcc, etrs);
> var searchCoord = new OpenLayers.LonLat(xcoord, ycoord);
> var searchCoordRep =  searchCoord.transform(hglipcc, mercator);
>
> Both returned the same wrong coordiantes: x= -881483.8794817993 and y= 
> -7.081154551613622e-10 where they should be x= -881320.416615 and y= 
> 4442714.696599.
>
> Also, i have tried to use the projection definitions and reproject 
> transformation directly from Proj4js and the returned results were 
> exactly the same.
>
> Finally i have tried to reproject to EPSG:4326 and still, the output 
> coordinates are strange: it returned lon=-7.918504416434706 and lat=0 
> where it should be lon=-7.917036 and lat=37.025879.
>
> Is this a known problem or is it something i'm doing wrong? Any 
> sugestions are more than welcome!
> Thanks in advance.
>
> Best regards,
> Hugo
>
>
>
>
>
>
> 3. Defined projections using new OpenLayers.Projection('EPSG:xxxxx');
>
> 4. the code used to reproject:
>
> var coordMarker = new OpenLayers.Geometry.Point(xcoord, ycoord); 
> //these coords in epsg 27492
>
> OpenLayers.Projection.transform(coordMarker, hg73ipcc, mercator);
>
> The coordinates introduced were x= 19300.924567 and y=-293208.893092 
> and the output was x=-1897829.842341831 and y=4442821.889195204. The 
> expected output should be x=-881320.416615 and y=4442714.696599
>
> I've tried to reproject from epsg:27492 to wgs84 and also got wrong 
> coordinates returned.
> Am i missing something here??? Any sugestions to solve this?
>
> -- 
> Hugo Martins
> LabNT - ISEGI UNL
> Campus de Campolide
> 1070-312 Lisboa
> N 38°43'56.84", W 9°9'35.74"
>
>
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