[GRASSLIST:7969] Fwd: Re: Fwd: Re: nad27/nad83 datum conversion for canada using Ntv2

[Feng Tan]

Hi,

Regarding the ntv2.gsb for canada in grass6.0

After I put NTV2_0.GSB file in the $GISBASE/etc/nad , I went to $GISBASE/etc 
edited datumtransform.table and replaced ntv1_can.dat with NTV2_0.GSB, I 
start a new nad27 location by chosing NTV2_0.GSB, then in my nad83 location I 
use v.proj command to do the nad27/nad83 conversion, it also failed:
it says:

pj_tranform() failed
cause: failed to load NAD27-83 correction file
Error in pj_do_transform


Please help!!!

Feng

----------  Forwarded Message  ----------

Subject: [GRASSLIST:7962] Re: Fwd: Re: nad27/nad83 datum conversion for canada 
using Ntv2
Date: Wednesday 17 August 2005 15:54
From: Feng Tan <feng at lynxseismicdata.com>
To: Paul Kelly <paul-grass at stjohnspoint.co.uk>
Cc: GRASSLIST at baylor.edu

Hi, Paul,

Thank you very much for the answer. I went to $GISBASE/etc edited
datumtransform.table and replaced ntv1_can.dat with NTV2_0.GSB, I start a new
location by chosing NTV2_0.GSB, but cs2cs failed. I did following

>IN_PROJ="+proj=utm +zone=10 +a=6378206.4 +rf=294.9786982 +no_defs

+nadgrids="$GISBASE/etc/nad/NTV2_0.GSB""

>OUT_PROJ="+proj=utm +zone=10 +a=6378137 +rf=298.257222101 +no_defs

+towgs84=0.000,0.000,0.000"

>echo "889298.45 8682992.65" |cs2cs -f %.7f $IN_PROJ +to $OUT_PROJ

*       * 0.0000000

what is wrong????

Thanks,

Feng

On Wednesday 17 August 2005 14:22, you wrote:
> On Wed, 17 Aug 2005, Feng Tan wrote:
> > I just did some testing about nad27/nad83 datum conversion for a point in
> > Alberta, Canada using GRASS6.0 comparing with ESRI ARCGIS9.1, following
> > is the result, it has about +-100m difference with or without NTV2_0.GSB.
> > I wish GRASS can implement newer version of Canadian National
> > Transformation NTV2_0.GSB nad27/nad83 datum shift grid file soon, so we
> > can use GRASS more confidently.
>
> GRASS (and PROJ.4) *can* use NTv2 GSB (binary) files and has been able to
> since the datum shifting support was added in 5.3. I'm not sure what
> your problem is here. What are you trying to change?
> Put the gsb file in the $GISBASE/etc/nad directory and edit the PROJ_INFO
> file for your NAD27 location to point to the new file.
>
> Paul

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