[postgis-devel] ST_SetValues (Generating raster from point data)

[Rémi Cura]

Hey,
I wrote some code for this
Check :
https://github.com/Remi-C/Postgres_Day_2014_10_RemiC/blob/master/Point_Cloud/Patch_to_raster/patch_to_raster.sql

I do a little more because I convert a pcpatch,
but you could take the part that takes a table of attributes (X,Y,Z,
whatever) and convert it to a raster.

ST_Setvalues is the fastest way  I found,
 but it is still *very *slow
I would advice to do this outside db or with efficient python/C code.
(for instance python-gdal ?)

Cheers,
Rémi

2014-10-28 18:04 GMT+01:00 David Haynes II <dahaynes at umn.edu>:

> Hello,
>
> I am hoping someone can help point me in the correct direction on this
> problem. I am trying to take a table of point data and generate a raster,
> using some NOAA data. These are the steps that I have taken so far.
> Everything is fine until step 4.
> The ST_SetValues does not work as I have currently implemented. Because
> each time a value is assigned it generates another raster.
> The examples I have seen using ST_SetValues require each recordset to be
> appended to each other. Does anyone have any knowledge about other psql
> functions that will allow me to transpose the recordset or append
> recordsets together. I am considering writing a custom function to do the
> task.
>
> 1. Convert text to geometry value
> 2. Determine raster extent using convexhull.
> 3. Generate raster using ST_AsRaster
> 4. Set raster cell values using ST_SetValues
>
> with noaa_raster as
> (
> select ST_AsRaster(p_bound.geom, 3.75::float8, 2.5::float8, '32BF', 1, 0)
> as rast
>  from (
>   --Generate polygon extent from all points
>   SELECT st_convexhull(ST_Collect(base.geom)) as geom
>   FROM (
>   --Converts text to geometry
>   select p.grid_id, ST_geomfromtext('POINT(' || p.longitude || ' ' ||
> p.latitude || ')',4326) as geom, p.value
>   from noaa p
>   ) base
>   ) p_bound
> )
> --distances are changed to make sure we fine the centroid of each raster
> cell
> select r.rid, p.grid_id, ST_SetValues(r.rast, 1,
> ARRAY[ROW(ST_geomfromtext('POINT(' || p.longitude + 1.875 || ' ' ||
> p.latitude - 1.25 || ')',4326), p.value)]::geomval[], True ) as rast
> from noaa p, noaa_raster r
>
>
> see
> http://postgis.net/docs/manual-dev/RT_ST_SetValues.html
>
> --
> David Haynes, Ph.D.
> Research Associate Terra Populus
> Minnesota Population Center
> www.terrapop.org
>
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>
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