[gdal-dev] Which Proj.4 transforms are available in GDAL?

[Andre Joost]

Am 25.08.2017 um 13:52 schrieb Even Rouault:

>
> For unsupported projections, add +wktext. A dummy WKT representation
> is then built that captures the full proj.4 string in a EXTENSION
> node. Can also serve for supported projections if you want to
> overrite the WKT -> proj.4 string conversion done by GDAL
>

This seems to work arbitrary.

gdalwarp -overwrite -dstnodata 0 -s_srs EPSG:3857 -t_srs "+proj=lcc 
+lat_1=13.31666666666667 +lat_2=14.25 +lat_0=13.783333 +lon_0=-89 
+x_0=500000 +y_0=295809.184 +k_0=0.99996704 +ellps=clrk66 +units=m 
+no_defs +towgs84=0,125,194,0,0,0,0 +wktext" -of GTiff ElSalvador.png 
ElSalvadorNAD27.tif
gdalsrsinfo ElSalvadorNAD27.tif >out.txt

does not add an EXTENSION to the WKT, but preserves the TOWGS84 values


ogr2ogr -s_srs EPSG:4326 -t_srs "+proj=lcc +lat_1=13.31666666666667 
+lat_2=14.25 +lat_0=13.783333 +lon_0=-89 +x_0=500000 +y_0=295809.184 
+k_0=0.99996704 +ellps=clrk66 +units=m +no_defs 
+towgs84=0,125,194,0,0,0,0 +wktext" LimitesNAD27.shp dptoA_WGS_1984.shp
gdalsrsinfo LimitesNAD27.prj >>out.txt

neither saves towgs84 or wktext

gdalsrsinfo "+proj=lcc +lat_1=13.31666666666667 +lat_2=14.25 
+lat_0=13.783333 +lon_0=-89 +x_0=500000 +y_0=295809.184 +k_0=0.99996704 
+ellps=clrk66 +units=m +no_defs +towgs84=0,125,194,0,0,0,0 +wktext"

adds TOWGS84 and EXTENSION.

Tested with GDAL 2.2.1

Perhaps you like to comment on 
https://gis.stackexchange.com/questions/253475/results-of-layers-created-with-a-custom-crs-are-loaded-with-a-generated-crs-in-q 
(with links to data).

Still confused,
André Joost