问题
I'm working with a geographic point using lat/long and need to find other points in our database within a 5 mile radius of that point. However, I can't seem to find out what the "units" are for STBuffer, it doesn't seem to conform to feet, miles, meters, kilometers, etc. The documentation only refers to them as "units", any suggestions? Thanks
[...] from geography::STGeomFromText('POINT(x y)', 4326).STBuffer(z).STIntersects(geography::STGeomFromText('POINT(' + CAST(v.Longitude as varchar(max)) + ' ' + CAST(v.Latitude as varchar(max)) + ')', 4326)) = 1
回答1:
STBuffer is in meters. More info here.
To convert, miles to meters, divide the number of miles by 0.0006213712
(i.e. 5 miles / 0.0006213712 = 8,046.72 meters)
回答2:
The unit of measurement depends on the spatial reference system in use. See this system view for details:
SELECT * FROM sys.spatial_reference_systems;
来源：https://stackoverflow.com/questions/2971293/sql-server-2008-geography-stbuffer-distance-measurement-units