Question

I need to find all the zipcodes with a certain range from a zipcode. I have all the zipcode lat/lon in a DB.

I have found two formulas online that vary slightly from each other. Which one is correct?

Formula 1:

def latRange = range/69.172
def lonRange = Math.abs(range/(Math.cos(Math.toRadians(zip.latitude)) * 69.172));
def minLat = zip.latitude - latRange
def maxLat = zip.latitude + latRange
def minLon = zip.longitude - lonRange
def maxLon = zip.longitude + lonRange

Formula 2: (is identical to formula one except for the following:)

def lonRange = Math.abs(range/(Math.cos(zip.latitude) * 69.172));

(The second one does not have Math.toRadians )
After I get the min/max Lat/Lon, I intend to search a DB table using a between criteria. Which formula is correct?

Answer 1

It depends on the units of your lat/long. If they are in degrees, you need to convert to radians.