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Postgis SRID value

I would like to know what the pragmatic meaning of SRID (spatial reference identifier) ​​is in postgis.

I really don’t understand why. Can anyone shed some light on this question?

For example, I noticed that the postigs function ST_GeomFromText(text WKT, integer srid)accepts such an (optional) parameter as the second argument. Why do I need to pass it to get postigs to turn a text representation into binary? What value does he add?

thank

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This is an example of the query that I am using. It uses the azimuthal projection of equal Lambert areas (ETRS89-LAEA, srid = 3035).

ST_GeomFromText('POINT(2843711.1098048678, 2279498.6551480694)', 3035);

If you don't pass srid, postgis will not know which spatial reference system to use.

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- , .. , , , .

-, - - (sh, Google), . , GPS, WGS84, , . , .

-, . , 3D . , , ( ), , .. , - .

, , SRID Postgis, , . Postgis Proj.4, SRID .

, , lat/lon, 4326 SRID 900913, , Google/Bing -, -

select st_astext(st_transform(st_setsrid(st_makepoint(-.5,52),4326),900913));
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