[Proj] towgs84 values for EPSG:27700

Hermann Peifer peifer at gmx.eu
Sun Feb 19 07:56:37 EST 2012


I am working with PROJ Rel. 4.7.1 and GDAL/OGR from trunk.

testepsg and gdalsrsinfo tell me that the towgs84 values for EPSG:27700 
are 375,-111,431,0,0,0,0 whereas cs2cs reports for the same EPSG code: 

Is this expected behaviour?


$ testepsg epsg:27700 | grep PROJ.4
PROJ.4 rendering of [epsg:27700] = +proj=tmerc +lat_0=49 +lon_0=-2 
+k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy 
+towgs84=375,-111,431,0,0,0,0 +units=m +no_defs

$ gdalsrsinfo epsg:27700 | grep PROJ.4
PROJ.4 : '+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 
+y_0=-100000 +ellps=airy +towgs84=375,-111,431,0,0,0,0 +units=m +no_defs '

$ cs2cs -v +init=epsg:27700 +to +proj=latlong +datum=WGS84
# ---- From Coordinate System ----
#Transverse Mercator
#       Cyl, Sph&Ell
# +init=epsg:27700 +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 
# +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs
# +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894
#--- following specified but NOT used
# +ellps=airy
# ---- To Coordinate System ----
#Lat/long (Geodetic alias)
# +proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0

More information about the Proj mailing list