[postgis-users] Selecting geocoded postal codes within a given distance ( miles for example )

[Hugh W. O'Brien]

Unfortunately, I must support all US postal codes so all of continental 
US and it's territories.  I might also have to include support for 
Canada in the future.

-- Hugh W. O'Brien

Paul Ramsey wrote:

> In the curious world of UTM (and planar systems in general), the 
> answer depends on where you are :)  Planar systems are local 
> transforms which make a range of spherical lat/lon coordinates into a 
> planar approximation. Because the world in spherical, it is very hard 
> to have a planar projection which is covers a very large area, is true 
> to shape, and is true to distance. So different parameterizatios of 
> planar projections are used for different locations. If you are on the 
> west coast of North America, then UTM10 (EPSG 26910) would be a good 
> UTM projection. But if you are in Texas, then a different projection 
> would be best.
>
> Question number one when picking a planar projection is "how spatially 
> big is your dataset?" Ie, what are its bounds in lat/lon?
>
> Paul
>
> Hugh W. O'Brien wrote:
>
>> Thanks for the reply Paul.  I had come to the conclusion that I had 
>> those 2 choice but wasn't sure which one was more difficult.  Thanks 
>> for pointing out which one is easier to implement.
>>
>> Now for a followup question?
>>
>> What's the best way to convert my geocoded postal codes to UTM?
>>
>> What would be the appropriate SRID of my new data set if I chose UTM 
>> as my new rectangular cooridinate set?
>>
>
>       __
>      /
>      | Paul Ramsey
>      | Refractions Research
>      | Email: pramsey at refractions.net
>      | Phone: (250) 885-0632
>      \_
>
>
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