jquery mobile and geolocation am i at address - jquery-mobile

Question

Does anyone have any demo sites that can show me how to tell whether I am at an address?
So I want to have a list of addresses and when I get close to one I want the application to raise an event that I can then respond to.
edit
A Lat/Long proximity alert would be even better actually

Answer 1

This code is php not javascript, but you should be able to get the idea of what is going on.
It is a formula I have used to check if an address is within a certain proximity of another address. (which is basically what you are wanting to do)
The actual formulas to work that out due to the curvature of the earth etc are quite complex, so this uses an approximation technique, and calculates a bounding box based on the distance_km.
You then just need to check if your address coordinates are within that bounding box.
I used google maps api to determine the lat/lon of each address.
function approx_boundingbox($lat, $lon, $distance_km) {
$lat_km_per_degs = array(
0 => 110.574,
15 => 110.649,
30 => 110.852,
45 => 111.132,
60 => 111.412,
75 => 111.618,
90 => 111.694);
$lon_km_per_degs = array(
0 => 111.320,
15 => 107.551,
30 => 96.486,
45 => 78.847,
60 => 55.800,
75 => 28.902,
90 => 0,
105 => 28.902,
120 => 55.800,
135 => 78.847,
150 => 96.486,
165 => 107.551,
180 => 111.320
);
// determine km per deg approxmation for lat
foreach ($lat_km_per_degs as $deg => $km) {
if ($lat < $deg) {
$lat_km_per_deg = $km;
}
}
// determine km per deg approxmation for lon
foreach ($lon_km_per_degs as $deg => $km) {
if ($lon < $deg) {
$lon_km_per_deg = $km;
}
}
// radius in deg
$lat_delta = ($distance_km / $lat_km_per_deg);
$lon_delta = ($distance_km / $lon_km_per_deg);
// calculate approximate box
$min_lat = $lat - $lat_delta;
$max_lat = $lat + $lat_delta;
$min_lon = $lon - $lon_delta;
$max_lon = $lon + $lon_delta;
return array($min_lat, $min_lon, $max_lat, $max_lon);
}