ST_Slope — Returns the surface slope of an elevation raster band. Useful for analyzing terrain.
raster ST_Slope(raster rast, integer band, text pixeltype
Returns the surface slope of an elevation raster band. Utilizes map algebra and applies the slope equation to neighboring pixels.
Given the following representation of a 3x3 neighborhood of pixels:
The equation for the pixel slope of cell E is: atan(sqrt(((c + 2f + i) - (a + 2d + g) / 8)^2 + (((g + 2h + i) - (a + 2b + c)) / 8) ^ 2))