[OSRS-PROJ] nad2nad bombing

Frank Warmerdam warmerdam at pobox.com
Tue Apr 22 09:51:58 EDT 2003

Jack Bowling wrote:
> I have a series of GPS-ed UTM points done in NAD83 datum but the topo charts I have on which to plot them are *old* NAD27 using Clarke ellipsoid.
> I tried the following on my linux box to convert. The input file is just a text file of UTM pairs:
> $ nad2nad -i 83,utm=10 -o 27,utm=10 -r ntv1_can.dat < /home/jb/docs/birds/NOS/bowron/txt/utm83.txt
> Rel. 4.4.7, 31 March 2003
> <nad2nad>:
> datum file: ntv1_can.dat, failed: failed to load NAD27-83 correction file
> program abnormally terminated
> The ntv1_can.dat file is in /usr/local/share/proj. I did this last year in June using the then current version of proj with perfect results. Perhaps somebody can show me the errors of my ways. 
> Yes, I know I should be using cs2cs instead of nad2nad if I want the ellisoid transform but the difference is within a few metres so it really is not that important on the scale of chart I am dealing with.


The nad2nad program only works with the US style datum shift files, not
the NTv1 or NTv2 files.  You will need to use cs2cs for this process;
however, it should not be difficult.  Something like the following
will likely work:

cs2cs +proj=utm +zone=10 +datum=NAD83 \
   +to +proj=utm +zone=10 +ellps=clrk66 +nadgrids=ntv1_can.dat \
   < /home/jb/docs/birds/NOS/bowron/txt/utm83.txt

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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