carbon poly tool sum SQL

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carbon poly tool sum SQL

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Last edited Nov 9, 2012

Created on Nov 9, 2012

This example computes the total carbon stored in a user-defined polygon by summing raster pixel values from a carbon dataset. It shows a SQL query using PostGIS raster functions, where `ST_Intersects` filters relevant pixels, `ST_PixelAsPolygon` converts pixels to polygons, and `ST_Transform` projects them to calculate area. The query also uses `ST_Value` to extract pixel carbon values, dividing by 100 and scaling by area to produce a total, alongside the polygon’s geographic area. The code relies on the PostGIS spatial extension and a `generate_series` cross join to iterate over a 10-by-10 grid of pixels.

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