Changes between Version 3 and Version 4 of UsersWikiNewbieDistanceMeasurement


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Timestamp:
Dec 2, 2009, 10:39:43 AM (14 years ago)
Author:
robe
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  • UsersWikiNewbieDistanceMeasurement

    v3 v4  
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    7 ST_Distance always returns in the units of the projection.
     7ST_Distance always returns in the units of the projection for the geometry data type.  For the [http://www.postgis.org/documentation/manual-1.5SVN/ch08.html#PostGIS_GeographyFunctions geography data type] introduced in PostGIS 1.5 -- units are always in meters and SRID is wgs 84 long lat (4326).
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    9 So if for example you chose SRID 4326 - then your measurement would be in degrees.
     9So if you are using geometry - for example you chose SRID 4326 - then your measurement would be in degrees. If you use geography -- your units are in meters.
     10With geography you can do much less but you need to know less and cna cover a wider range of distance.  With geometry data type you can do a lot more geometric processing, but you need to understand spatial reference systems etc and how to transform between them to get the most out of them.
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    1112It is best to use a meter based or feet based projection for measurement.