[GRASS-user] A question about raster map resolutions

Micha Silver micha at arava.co.il
Tue Sep 20 22:33:27 PDT 2016



On 21/09/2016 02:30, Rich Shepard wrote:
>   The LiDAR source location has x- and y-resolution of 3 feet
> (international) and several thousand cells east-west and north-south.
> g.region -p for this location displays:
>
> projection: 99 (unnamed)
> zone:       0
> datum:      ** unknown (default: WGS84) **
> ellipsoid:  grs80
> north:      1286590.24500872
> south:      1240510.24500872
> west:       634966.76150938
> east:       664972.76150938
> nsres:      3
> ewres:      3
> rows:       15360
> cols:       10002
> cells:      153630720
>
>   When in the project location g.region -p produces:
>
> projection: 99 
> (NAD_1983_HARN_StatePlane_Oregon_North_FIPS_3601_Feet_Intl)
> zone:       0
> datum:      nad83harn
> ellipsoid:  grs80
> north:      588219.90693215
> south:      536993.58817534
> west:       7524575.13218961
> east:       7561596.20977101
> nsres:      2561.31593784
> ewres:      1851.05387907
> rows:       20
> cols:       20
> cells:      400
>
>   I want to understand why the nsres is now 2561+ feet, the ewres now 
> 1851+
> feet, and the numbers of rows and columns has decreased so drastically.
>
> Looking forward to learning,
>

The r.proj module has a flag to get the new resolution settings when 
reprojection data from one LOCATION to another. Before reprojecting the 
map from ** unknown (default: WGS84) ** to  nad83harn, try r.proj -g. 
Then use those parameters to set the region in the new CRS/LOCATION. 
That will leave you with the same number of row and columns in the new 
projection.
Then you'll need to do r.proj again to get the raster reprojected with 
these new region settings.

> Rich
>
>
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user

-- 
Micha Silver
Arava Drainage Authority
+972-523-665918

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20160921/fbbbb19b/attachment-0001.html>


More information about the grass-user mailing list