[R-sig-Geo] writeGDAL produce strage value range

[Roger Bivand]

On Mon, 31 Aug 2009, "Häring, Tim (LWF)" wrote:

> Hello List !
>
> With writeGDAL I exported a grid as Erdas Imagine Image:
> writeGDAL(mygrid, fname = "grid6426.img", driver = "HFA",
> type = "Float32")
>
> If I open this Image in ArcGIS all I see is a solid black box with a strange value range from 1.7549e-038 to 3.40282e+038. I can identify the values of single grid-cells and see that the values in my grid were right. But all I see is a black rectangle.
>
> Is this a RGDAL/GDAL problem or is it a ArcGIS problem? Maybe there is 
> someone having the same problem - and hopefully with a solution.

ArcGIS typically makes assumptions about symbology that may not be what 
you intend. Make sure that it is displayed in classified mode. If need be, 
build the statistics first using the appropriate toolbox function. This 
also used to be an issue with GTiff. You may also need to use create 
options to find the style of file that ArcGIS likes least poorly, review:

http://www.gdal.org/frmt_hfa.html

Roger

>
> Thanks!
>
> Cheers,
> TIM
>
> -------------------------------------------------------
> Tim Häring
> Bavarian State Institute of Forest Research
> Department of Forest Ecology
> Am Hochanger 11
> D-85354 Freising
>
> http://www.lwf.bayern.de
>
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>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no