Hi, Regina, The matter seems to be more complicated than that.
I just tried the same method on a large polygon and found a table of geohash values at different granularity, [image: image.png] Can one understand that the coverage of this polygon involves all these geohash grid? A clear understanding of what these mean is important. Regards, David On Tue, 22 Nov 2022 at 21:40, Regina Obe <[email protected]> wrote: > David, > > > > Sorry for the delay. For points ST_GeoHash is an exact location. > > For everything else it’s really the hash of the bounding box. Since bound > box covers more area, the length of the hash is shorter. > > > > Here is an example to demonstrate: > > > > SELECT ST_GeoHash(ST_GeomFromText('POINT(-20.234 50.897)', 4326)); > > > > Returns g919e9d098kp4n6m82ys > > > > SELECT ST_GeoHash(ST_GeomFromText('LINESTRING(-20.234 50.897, -20.235 > 50.908)', 4326)); > > Returns: g919e > > > > Note how the hash of the second is a subset of the first? So that means > any geometry that starts with g919e essentially falls in the bounding box > that the linestring forms. > > > > Also note that the above answer is equivalent to: > > > > SELECT ST_GeoHash(ST_GeomFromText('LINESTRING(-20.234 50.897, -20.235 > 50.908)', 4326)::box2d); > > > > Hope that clarifies things, > > Regina > > > > > > > > *From:* postgis-users [mailto:[email protected]] *On > Behalf Of *Shaozhong SHI > *Sent:* Monday, November 14, 2022 3:46 AM > *To:* PostGIS Users Discussion <[email protected]> > *Subject:* [postgis-users] Understanding of Geohash of a line feature > > > > Any detailed explanation on Gehash of a line feature? > > > > The following works and returns output. > > > > ST_geoHash(ST_transform(a_line_geometry,4326)) > > > > However, what exactly the output means? > > > > Anyone knows what the output means? > > > > Regards, > > > > David > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users >
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