Hi
For a locator store the Haversine formula will be adequate.
This calculates the great-circle distance between two points – that
is, the shortest distance over the earth’s surface – giving an ‘as-the-
crow-flies’ distance between the points (ignoring any hills, of
course!).
Haversine formula:
a = sin²(Δlat/2) + cos(lat1).cos(lat2).sin²(Δlong/2)
c = 2.atan2(√a, √(1−a))
d = R.c
where R is earth’s radius (mean radius = 6,371km);
note that angles need to be in radians to pass to trig functions!
JavaScript:
var R = 3959;//miles
or
var R = 6371; // km
var dLat = (lat2-lat1).toRad();
var dLon = (lon2-lon1).toRad();
var lat1 = lat1.toRad();
var lat2 = lat2.toRad();
var a = Math.sin(dLat/2) * Math.sin(dLat/2) + Math.sin(dLon/2) *
Math.sin(dLon/2) * Math.cos(lat1) * Math.cos(lat2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
This is used for the SELECT statement in Google's own store locator
http://code.google.com/apis/maps/articles/phpsqlsearch_v3.html#outputxml
Regards Davie
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