ST_Flow_direction
Updated at:
Computes the flow direction of an area using the D8 algorithm applied to digital elevation model (DEM) data.
Syntax
float8[] ST_flow_direction(raster rast, Box box)Parameters
| Parameter | Description |
|---|---|
rast | The raster object. Currently must be a single-band DEM. |
box | The world space of the area to analyze. |
Description
ST_flow_direction applies the D8 flow direction algorithm to DEM data within the specified area and returns the results as an array of float8 values.
The rast parameter currently must be a single-band raster containing DEM values.
Example
SELECT st_flow_direction(rast, '((-202286.94,2232375.16),(-202135.0,2232225))'::box)
FROM t_overflow
WHERE id = 2;Output:
st_flow_direction
--------------------------------------------------------------------------------
{2,2,2,4,4,8,2,2,2,4,4,8,1,1,2,4,8,4,128,128,1,2,4,8,2,2,1,4,4,4,1,1,1,1,4,16}
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