[GRASS-user] External Database and projections

[Lorenzo Bottaccioli]

Hi Stefan,

With a distributed infrastructure I mean that the the computation and the
data are deployed in a distributed platform. The data then will be
available trough WWW but the aim of the infrastructure is not on the
visualization of the maps but on providing the information in JSON or
similar format regarding the information of the raster maps.

Cheers

Lorenzo

2015-10-14 16:09 GMT+02:00 Blumentrath, Stefan <Stefan.Blumentrath at nina.no>:

> Hi Lorenzo,
>
>
>
> What do you mean with a «distributed infrastructure”?
>
>
>
> Do you want to make the rasters available via WWW or in your
> company/institution?
>
> There are other options to share data than PostGIS… Within an organization
> your GRASS GIS database on NFS would be a much, much more efficient one.
>
> For WWW-publishing WCS is an option…
>
>
>
> Anyway, writing copies of your raster maps to DB (PostGIS) – if that is a
> fix requirement - is less of a problem (if they are not too heavy), than
> writing to DB, reading from DB for processing in GRASS and writing result
> back to DB…
>
>
>
> If your aim is to add “zonal statistics” to a vector layer in PostGIS I
> would do the raster operation in GRASS and then join the result to PG…
>
>
>
> Cheers
>
> Stefan
>
>
>
>
>
> *From:* Lorenzo Bottaccioli [mailto:lorenzo.bottaccioli at gmail.com]
> *Sent:* 14. oktober 2015 15:44
> *To:* Blumentrath, Stefan <Stefan.Blumentrath at nina.no>
> *Cc:* Dylan Beaudette <dylan.beaudette at gmail.com>; Markus Neteler <
> neteler at osgeo.org>; GRASS user list <grass-user at lists.osgeo.org>
>
> *Subject:* Re: [GRASS-user] External Database and projections
>
>
>
> 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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