[Proj] Question on +czech option

[Melita Kennedy]

I am wondering if the parameter/option +czech is working correctly. 

If anyone is unfamiliar with it, this option is used with +proj=krovak, the Krovak projection used in former Czechoslovakia (and current Czech Republic). 

The 'native' Krovak has positive south, west axes (given in that order according to EPSG). Many Czech users are happy to use east, north axes in order to use various software packages that don't support multiple axis directions. 

Using an input point of latitude = 50, longitude = 20, I got these results (point is a little nonsensical due to using Ferro prime meridian in the tests):

with czech (2065)
cs2cs +to +proj=krovak +ellps=bessel +pm=ferro +x_0=0.0 +y_0=0.0
          +lon_0=42d30'E +lat_0=49d30'N +k_0=0.9999 +czech +no_defs

   cs2cs - PJ lib: 1589829.67     864777.51
   forward 2065  :  864777.51    1589829.67 (Esri projection engine)

without czech (5211)
cs2cs +to +proj=krovak +ellps=bessel +pm=ferro +x_0=0.0 +y_0=0.0
          +lon_0=42d30'E +lat_0=49d30'N +k_0=0.9999 +no_defs

   cs2cs - PJ lib: -1589829.67   -864777.51
   forward 5211  : -1589829.67   -864777.51 (Esri projection engine)

So without the +czech option, we get east, north axes. With +czech, we get values in west, south axes order, rather than south, west. Is this correct behavior? 

Disclosure: I work at Esri and I'm on the subcommittee that maintains the EPSG Geodetic Registry. 

Melita

Melita Kennedy
Esri Sr. Product Engineer