Detailed st_mapalgebra reference?

[Robert Burgholzer]

Thanks Regina!

On Tue, Jul 30, 2024 at 2:28 PM Regina Obe <lr at pcorp.us> wrote:

> For basic boolean logic, I would highly suggest just using Reclass, as
> it’s much faster
>
> https://postgis.net/docs/RT_ST_Reclass.html
>
>
>
> Generally speaking I think any algebraic operations and I recall even CASE
> statements allowed in SQL are allowed though I haven’t fully tested that.
>
> If you are doing more complex things than that, you probably should just
> create a mapalgebra callback function to use.
>
>
>
> There are some already part of PostGIS proper that are mostly written in
> plpgsql so you can peak and see how they work
>
>
> https://postgis.net/docs/RT_reference.html#Raster_Processing_MapAlgebra_Callbacks
>
>
>
> and then stuff into - https://postgis.net/docs/RT_ST_MapAlgebra.html
>
>
>
> *From:* Robert Burgholzer <rburghol at vt.edu>
> *Sent:* Tuesday, July 30, 2024 2:09 PM
> *To:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Subject:* Detailed st_mapalgebra reference?
>
>
>
> We are doing a ton of precip raster analysis and rectification, and we are
> struggling to find details on the algebraic expressions that we can use,
> ie, "[rast1] + [rast2]" is great if we are adding, but we are also
> interested in boolean calculations etc.
>
>
>
> The basic postgis reference page is great for understanding syntax but I
> am looking for recipes or a large raster calculator reference.
>
>
>
> Thanks on advance,
>
> Robert
>
> --
> Robert W. Burgholzer
>  'Making the simple complicated is commonplace; making the complicated
> simple, awesomely simple, that's creativity.'  - Charles Mingus
>
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