Projection systems

Definition of various projection systems can be found at the website spatialreference.org. Using org some functionality is available to convert projection system information to well known text or proj.4 format. The following code snippet is an example to translate information from a .prj file to proj.4 format. However ogr only provides a limited set of conversions.

Currently we require projection from world coordinates (wgs84) to meters (amersfoort new). The proj.4 definition of this projection is as follows (see also spatialreference.org).
"+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs"

update: ogr2ogr now supports:
"ogr2ogr -t_srs EPSG:28992 rivers_rdnew.shp rivers.shp", see example later on this page.

More examples for using ogr can be found at California soil resource lab

     public static string  EsriToProj4(string esriProjectionPath)
     {
           OSGeo.OSR.SpatialReference oSRS= new SpatialReference("");
           if (oSRS.SetFromUserInput(esriProjectionPath)!=Ogr.OGRERR_NONE)
           {
               throw new ApplicationException(string.Format("Error occured translating {0}",esriProjectionPath));
           }

            string proj4OutputString;
            if( oSRS.ExportToProj4(out proj4OutputString)==Ogr.OGRERR_NONE)
            {
                return proj4OutputString;
            }
            else
            {
                throw new ApplicationException("Export to proj4 failed");
            }
    }

This code snippet was based on the original c++ version by Frank Warmerdam. I have added the projection files contained with ArcMap. I don't think we should distribute these.

proj.4 is a utility for converting coordinates from one system to another. Proj.4 is written in c++ and can be downloaded from the Proj.4 website. Gdal /Ogr(currently version 1.61) depends on Proj.4 to convert raster or shapefiles from one coordinate system to another. To use proj.4 (windows) it is necessary to set the path to NAD27 grid shift files in an environmental variable, example: set PROJ_LIB=C:\Software\PROJ\NAD (we have to figure out some way to do this in deltashell).

The Shapelib library by Frank Warmerdam supports reprojection of shapefiles. I don't know if the syntax to define projections conforms to the proj.4 syntax.

Example
the following example projects file rowtest to row3, moving data from Stateplane NAD83 zone 1002 to utm zone 16 in meters

shpproj rowtest row -i="init=nad83:1002 units=us-ft" -o="proj=utm zone=16 units=m"
shpproj rowtest row3 -o="proj=utm zone=18 units=m" -i="zone=16 proj=utm units=us-ft"
shpproj rowtest row3 -o="proj=utm zone=18 units=m" 
shpproj rowtest row3 -i=myfile.prj -o=geographic
shpproj rowtest row3 -is=myfile.prj

You can try using ogr2ogr yourself by executing project_to_rdnew.cmd in the following attachment it will convert rivers.shp and project it from "GCS_WGS_1984" to "Amersfoort / RD New". The commandline for this is: "ogr2ogr -t_srs EPSG:28992 rivers_rdnew.shp rivers.shp"