[GRASS-user] External Database and projections

[Lorenzo Bottaccioli]

Hello,

Thanks for your suggestion. The point is that I need do develop a
distributed infrastructure hence I need to store the raster in to a DB
after the creation. Once I have created the raster immages I'll need to do
some simple multiplication and I thought to do them with r.mapcalc. Then
I'll use a vector map in order to extract the values of the raster.

So i think I'll have to use inevitably a DBMS to store the raster images
produced with grass. I'm I wright?

Tnx again regards

Lorenzo

2015-10-08 8:40 GMT+02:00 Blumentrath, Stefan <Stefan.Blumentrath at nina.no>:

> Hi Dylan,
>
>
>
> Yes, r.external and r.external.out works pretty well with TGIS. Here is a
> discussion in this regards I had mainly with Sören…
>
> https://lists.osgeo.org/pipermail/grass-user/2013-December/069377.html
>
>
>
> I have used r.external/r.external.out in TGIS for a while (with compressed
> GeoTiffs, btw you should not pre-define the predictor for LZW-compression
> as long as you are not sure that all raster maps are of the same type
> (CELL/FCELL/DCELL)), but went back to using internal GRASS format, because
> external links are a bit tricky to use on NFS and from different OS (or if
> data is moved):
>
> https://trac.osgeo.org/grass/ticket/2660
>
>
>
> Another minor (and often neglectable) drawback of using r.external is that
> file names and map names get out of sync if you rename maps. g.rename
> renames only the GRASS internal map name (modifies the link) the underlying
> data file is not touched and stays with the old name…
>
>
>
> Cheers
>
> Stefan
>
>
>
>
>
> *From:* Dylan Beaudette [mailto:dylan.beaudette at gmail.com]
> *Sent:* 8. oktober 2015 00:17
> *To:* Markus Neteler <neteler at osgeo.org>
> *Cc:* Blumentrath, Stefan <Stefan.Blumentrath at nina.no>; GRASS user list <
> grass-user at lists.osgeo.org>
> *Subject:* Re: [GRASS-user] External Database and projections
>
>
>
> The use of r.external makes a lot of sense when dealing with very large
> files. Does the use of "external" files work as expected in all of the new
> t.* modules?
>
>
>
> Thanks,
>
> Dylan
>
>
>
> On Wed, Oct 7, 2015 at 12:09 PM, Markus Neteler <neteler at osgeo.org> wrote:
>
> On Wed, Oct 7, 2015 at 12:55 PM, Blumentrath, Stefan
> <Stefan.Blumentrath at nina.no> wrote:
> ...
> > My suggestion is to not use PostGIS for big rasters, unless you have to,
> > because you want to use the data in a specific application for example.
>
> Note r.external and r.external.out of GRASS GIS 7 for avoiding data
> duplication:
>
> https://grass.osgeo.org/grass70/manuals/r.external.html
> https://grass.osgeo.org/grass70/manuals/r.external.out.html
>
> Here an example:
>
> # register (rather than import) a GeoTIFF file in GRASS GIS:
> r.external input=terra_lst1km20030314.LST_Day.tif output=modis_celsius
>
> # define output directory for files resulting from subsequent calculations:
> r.external.out directory=$HOME/gisoutput/ format="GTiff"
>
> # perform calculations (here: extract pixels > 20 deg C)
> # store output directly as GeoTIFF file, hence add the .tif extension:
> r.mapcalc "warm.tif = if(modis_celsius > 20.0, modis_celsius, null() )"
>
> # cease GDAL output connection and turn back to write standard GRASS
> raster files:
> r.external.out -r
>
> # use the result elsewhere
> qgis $HOME/gisoutput/warm.tif
>
> Best
> Markus
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