[Proj] Cassini coordinate reprojection problem

Chris Faulkner christopher.faulkner at ntlworld.com
Tue Mar 15 18:12:47 EST 2005


I have been sent some coordinates reprojected by another package that do
not match what I am getting out of proj4.

The projection is from Cassini to Transverse Mercator, details below.

I think the other package is genamap. The TM coordinate reported by
genamap from the reprojection is 535543,175269. I have downloaded
geotrans and it gives exactly the same result.

Proj4 gives this - 535596.86       175379.03. I am on RedHat Linux 9.0,
running 4.4.9

Most likely, I am driving proj4 incorrectly. Here is what I do

# Convert to lat /long (it doesn't matter if I remove the es and a
chris at dinky /cygdrive/c/mapmarketing/software/tabrunner
$ invproj +ellps=airy +proj=cass +a=6377563.3959999 +es=0.0066705398
+lat_0=51.2695503 +lon_0=0.665434
-49630.956 21390.870
0d2'55.474"W    51d27'34.779"N

# Convert the lat / long to Transverse Mercator
chris at dinky /cygdrive/c/mapmarketing/software/tabrunner
$ proj +ellps=airy +proj=tmerc +lat_0=49 +lon_0=-2 +x_0=400000
0d2'55.474"W    51d27'34.779"N
535596.86       175379.03

proj +proj=list gives an error message. Projection initialization
Cause: unknown projection id

Any help would be most welcome !



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