[postgis-users] Postgis raster tutorial

georgew gws293 at hotmail.com
Thu Apr 17 04:24:37 PDT 2014

As a new raster user I have found it extremely difficult to come to grips
with the task of creating a raster table with postgis, in particular from an
existing vector table, a task which is really trivial when done with some
existing s/w packages ( i.e. SAGA, GRASS etc..). Most of the examples I
could find were based  on the use of raster2pgsql which implies the prior
existence of a raster file created with an external package, not on using
postgis native capabilities to create such a raster. If you already have a
raster file,  postgis has no problem creating a table from it, but what if
you don't? Should you be forced to use one of the external packages?
The postgis manual has a total of two (2) examples on how to create a raster
table with st_asraster, although there are ten (10) different variants. My
point is not a criticism of postgis raster, at the contrary, a suggestion
that it could be much more useful if properly explained to users not
familiar with it. In other words a good postgis raster tutorial would go a
long way to convince users to at least try postgis raster by itself without
recourse to external packages (except perhaps for the visualisation of the
rasters). Specifically, how to create with postgis a raster table from a
vector table, how to extract values from one of the vector attributes and
store them in the raster, resulting in a raster identical to what would have
been created with raster2pgsql. I, with my ignorance of the topic, have not
been able to do that yet.
If such a tutorial has already appeared somewhere I would be delighted to be
pointed in that direction.
Many thanks

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