Timeline for geometry vs geography for distance measurement and large dataset
Current License: CC BY-SA 4.0
8 events
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| Oct 12, 2022 at 10:56 | comment | added | geozelot |
Pretty sure they transform all exemplary data after insert to the (now deprecated, btw.) EPSG:2163 Equal Area projection, which has metre as unit!
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| Oct 12, 2022 at 10:46 | vote | accept | JPFrancoia | ||
| Oct 12, 2022 at 10:40 | comment | added | JPFrancoia | Oooooops, the SRID is 2163 after a couple of transforms | |
| Oct 12, 2022 at 10:13 | comment | added | JPFrancoia |
What you're saying seems to make sense, but what about the example in the book (see image in previous comment)? The tables in the DB store coordinates as long/lat geometries, but the ST_DWithin function uses meters as the distance threshold.
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| Oct 12, 2022 at 10:03 | comment | added | geozelot |
I am absolutely certain. That is, of course it works on GEOMETRY(4326), but distance parameter and return value will be in degree! From the docs: "For geometry: The distance is specified in units defined by the spatial reference system of the geometries.
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| Oct 12, 2022 at 9:37 | comment | added | JPFrancoia |
Are you absolutely certain that ST_DWithin won't work on 4326 geometries? I'm a bit confused, I'm reading From the 2nd edition of PostGIS in Action and they show a query with this function, using meters and 4326 geometries: ibb.co/NmVRGg1.
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| Oct 12, 2022 at 9:20 | history | edited | geozelot | CC BY-SA 4.0 |
added 90 characters in body
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| Oct 12, 2022 at 9:14 | history | answered | geozelot | CC BY-SA 4.0 |