[GRASS-user] Import/conversion problem
woklist at kyngchaos.com
Fri Feb 11 15:39:53 EST 2011
Hmm, something I've seen for a while (Mac only), and it didn't improve with the latest MrSID DSDK, is that there are errors in retrieving GCS info from a sid with GDAL - some parameters are reported wrong or dropped. It hasn't been a problem for me since I usually know the projection of the SID and can override it in the conversion.
It looks like the MrSID DSDK tool mrsiddecode gets it right.
On Feb 11, 2011, at 1:08 PM, Adam Dershowitz, Ph.D., P.E. wrote:
> I am also working on OS X. But, I am using the MrSID plugin, from William Kyngesburye. So it seems that both gdalwarp and r.in.gdal are willing to import it. But, maybe I will try to search around for the apps that you are referring to, to see if they might do a better job on the conversion.
> Are you suggesting that the MrSID plugin that I have is working, but is loosing reference data along the way?
> On Feb 11, 2011, at 10:47 AM, Stuart Edwards wrote:
>> MrSID files are a bit tricky. This is a proprietary format owned by LizardTech (see http://www.gdal.org/frmt_mrsid.html). That being said, they freely provide decode tools at their website (http://www.lizardtech.com/). Working on OS X, I use their Raster_DSDK in a little command line routine to convert the file to a geotiff (tifg) and then import it into GRASS with r.in.gdal. Note that the MrSID format is very efficient and boils a quad down to about 1.5 Gb. This will become 3 or 4 times greater as a tif so make sure you have plenty of room to store it and process it. I use an old version of Expressview (a LizardTech viewer that used to be available for OS X) to look at the image and determine the coordinates of the bit that I really want in order to minimize the resulting file sizes.
>> AFAIK there are no open source apps that deal with MrSID directly (for those that do, you have to install your own version of the decoder first)
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
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