Changing Coordinate system from custom CRS?

Question

Is it possible to reproject a shapefile from a custom CRS?

My example is as below but the EPSG is not a valid EPSG supported file.

    ogr2ogr -s_srs EPSG:100000 -t_srs EPSG:27700 output.shp input.shp

Answer 1

Generally yes, if the projection adopted in your custom CRS is supported by GDAL & Proj4. For instance, you could use the Proj4 format in place of EPSG:100000:

ogr2ogr -s_srs "+proj=utm +zone=30 +ellps=intl +towgs84=-90,-100,-120,0,0,0,0 +units=m +no_defs " -t_srs EPSG:27700 output.shp input.shp

Srs_def can be a full WKT definition (hard to escape properly), or a well known definition (i.e. EPSG:4326) or a file with a WKT definition. (Source: http://www.gdal.org/ogr2ogr.html)