Detailed st_mapalgebra reference?

[Regina Obe]

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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