Given coordinates, how do I get all the Zip Codes within a 10 mile radius?

Question

I have a location (latitude & longitude). How can I get a list of zipcodes that are either partially or fully within the 10 mile radius of my location?

The solution

Answer 1

Start with a zip code database that contains zipcodes and their corresponding latitude and longitude coordinates:

http://www.zipcodedownload.com/Products/Product/Z5Commercial/Standard/Overview/

To get the distance between latitude and longitude, you will need a good distance formula. This site has a couple variations:

http://www.meridianworlddata.com/distance-calculation/

The "Great Circle Distance" formula is a little extreme. This one works well enough from my experience:

sqrt(x * x + y * y)

where x = 69.1 * (lat2 - lat1)
and y = 69.1 * (lon2 - lon1) * cos(lat1/57.3)

Your SQL Query will then look something like this:

select zd.ZipCode
from ZipData zd
where 
    sqrt(
        square(69.1 * (zd.Latitude - @Latitude)) +
        square(69.1 * (zd.Longitude - @Longitude) * cos(@Latitude/57.3))
    ) < @Distance

Good luck!