[GRASS5] Problem converting NAD27 to NAD83.

[Paul Kelly]

Hello Craig

On Thu, 7 Apr 2005, Craig Funk wrote:

> Hello, I am having problems with v.proj (and r.proj) when projecting vectors 
> from a NAD27 database to NAD83 use GRASS 6.0
>
> This is the output from the v.proj command:
>
> Input Projection Parameters: +proj=utm +zone=10 +a=6378206.4 +rf=294.9786982 
> +no_defs +nadgrids=ntv1_can.dat
> Input Unit Factor: 1
>
> Output Projection Parameters: +proj=utm +zone=10 +a=6378137 +rf=298.257222101 
> +no_defs +towgs84=0.000,0.000,0.000
> Output Unit Factor: 1
> WARNING: The vector 'lines' already exists and will be
>         overwritten.
>
> Creating vector file...
> pj_transform() failed
> cause: failed to load NAD27-83 correction file
> Error in pj_do_transform

The most common cause for that error is that the points you are trying to 
re-project fall outside the area covered by the datum shift grid file 
(ntv1_can.dat). Are you sure it is the correct file for your area 
(Canada).

If you are having trouble with the grid shift files you could try doing a 
less precise datum transformation using a 3 or 7-parameter transformation. 
Re-run g.setproj in the NAD27 location to set up your datum parameters.

Paul


>
> This is my PROJ_INFO file:
>
> name: UTM
> datum: nad83
> dx: 0.000000
> dy: 0.000000
> dz: 0.000000
> proj: utm
> ellps: grs80
> a: 6378137.0000000000
> es: 0.0066943800
> f: 298.2572221010
> zone: 10
>
>
> This is my DEFAULT_WIND file:
> proj:       1
> zone:       10
> north:      6665000
> south:      5300000
> east:       696621
> west:       332705
> cols:       72783
> rows:       273000
> e-w resol:  5.00001374
> n-s resol:  5
>
> Any suggestions?
> --
> Craig Funk
> funkmeister -at- lynxseismicdata -dot- com
>
> _______________________________________________
> grass5 mailing list
> grass5 at grass.itc.it
> http://grass.itc.it/mailman/listinfo/grass5
>