[OSRS-PROJ] nad2nad bombing

Jack Bowling jbinpg at shaw.ca
Tue Apr 22 11:05:18 EDT 2003

** Reply to message from Frank Warmerdam <warmerdam at pobox.com> on Tue, 22 Apr 2003 09:51:58 -0400

> 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.
> Jack,
> 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

Works like a charm, Frank. Thanks a bunch. I guess the internals must have changed since a few versions ago cuz nad2nad worked with the ntv1_can.dat previously.

Jack Bowling Prince George, BC mailto:jbinpg at shaw.ca
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