Re: Zip Code Proximity

On Thu, 18 May 2000, Jeff Hoffmann wrote:

> Andy Lewis wrote:
> >
> > Actually I was thinking more on the lines of:
> >
> > select location from test where location @ '((31.6283,93.6347), 1.39)'::circle;
> >
>
> that works just great, assuming that you can accurately calculate the
> radius of the circle that you're searching for.
>

I'll already have the mileage from an html form and the initial
zip. Should work just fine. It doesn't have to be exact just close.

> > If Zylks, LA (lat/lon = 32.9696,93.9801) is also in the DB.
> > The above query should select Zylks since 1.39 * 62.1 = 86 miles approx.
> > 86 miles is about correct for those two zip codes.
> >
> > Wouldn't this be much easier?
>
> to me, the big question is how you're calculating the radius & if you're
> taking into account the curvature of the earth so that 62.1 changes in
> different parts of the country.  if you've taken that into
> consideration, great.  it's probably going to be ok to flatten the earth
> for an area that size, though.
>

I don't plan on using anymore than a 100 miles, so that should work ok,
I'd think.

> > Is the data type POINT index-able?
> >
>
> unfortunately, not in a really useful way for you.  plus, the optimizer
> probably wouldn't use the index any.  it's a small data set, something
> around 35k-40k records, right?
>

I'm not sure how many records are in the zip code DB that I currently
have, shouldn't be much more than that though.

Andy