[postgis-users] How does ST_Slope works ?

[Francois Hugues]

Hello list,

 

I have two (basics) questions about ST_Slope about somethings I don't
understand.

 

1. To know which Pixeltype I had to use, I tried to use st_bandpixeltype
which told me my pixels were 32BSI type but my results using this type
are 0 or 1 and if I try another type like 32BF, results seems to be more
useful. Does someone have an explanation about this weird difference ?
What is the unit used by st_slope ?

 

2. My raster is a tiled one and as you can see on both pictures,
ST_Slope gives no results for pixels located at the border of each tile.
I can understand it is impossible to find the slope for the pixels which
make the border of the raster, but is there not a way to have complete
results for the tile in the middle of the raster and thus use the
neighboring tiles.

 

Hugues.

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