[postgis-users] Buffer/Nautical Miles

[Blake Crosby]

Bruce,

Ok thanks.. that explains a lot. So really my only course of action is 
to transform to UTM, do my buffer, then transform back to WGS84?

Blake

Bruce Rindahl wrote:
> A nautical mile is 1 minute measured along a great circle on a sphere 
> (such as the equator or a longitude line).  Thus your query will not 
> work- it will be too short in the x direction.  If you are using UTM a 
> nautical mile is about 1852 meters.
> 
> Bruce
> 
> Blake Crosby wrote:
>> I'm trying to create "circles" by using the buffer function around a 
>> point.
>>
>> The radius values i'm working with are in nautical miles. The 
>> definition of a nautical mile is 1 minute of 1 degree.
>>
>> Since this unit of measurement is based on a degree, and WSG84 is 
>> based on degrees of lat/long (and not meters like UTM) will the 
>> following be valid for a circle with a radius of 2 nautical miles 
>> around point (72.3,-45.3)?
>>
>> st_buffer(st_geomfromtext('POINT(-45.3 72.3)', 4326), 0.0166667*2)
>>
>> I'm trying to troubleshoot a problem I'm having and want to rule out 
>> any issues with my usage of buffer.
>>
>> Blake
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>>
> 
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