[gdal-dev] ogr2ogr

[Even Rouault]

Hi,

My understanding about the WGS84 vs NAD83 issue is that for most practical 
usages they are pretty much the same, and I believe that PROJ.4 makes that 
assumption. So, there's no datum transformation.

See http://www.mentorsoftwareinc.com/resource/Nad83.htm, 
http://www.geod.nrcan.gc.ca/faq_e.php#23, 
http://n2.nabble.com/Proj4-datum-transform-assumption-Question-td1111052.html 
for others references on the subject.

Le Monday 03 November 2008 20:12:29 Limei Ran, vous avez écrit :
> Hi:
>
> I am trying to project a shapefile from WGS84 to NAD83 using the
> following command:
> ogr2ogr -s_srs "+proj=latlong +datum=WGS84"  -t_srs "+proj=aea
> +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80
> +datum=NAD83 +units=m +no_defs "   temp_des.shp temp_src.shp
>
> Could you tell me whether there is datum transformation from WGS84 to
> NAD83 in the projection?  I checked the two shapefiles at very high
> scale.  I did not see any diffference.  I am wondering whether the datum
> transformation happened in this command.  If not, how can I make it happen?
>
> Thank you,
>
> Limei
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