// Execute logic to enforce geofence if required parameters are present
if(params.latitude && params.longitude && params.center_latitude && params.center_longitude && params.geofence_radius) {
var R = 6371e3; // metres
var φ1 = degrees_to_radians(params.center_latitude);
var φ2 = degrees_to_radians(params.latitude);
var Δφ = degrees_to_radians(params.latitude-params.center_latitude);
var Δλ = degrees_to_radians(params.longitude-params.center_longitude);
var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
Math.cos(φ1) * Math.cos(φ2) *
Math.sin(Δλ/2) * Math.sin(Δλ/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
if(d > params.geofence_radius) {
params.alert = 1;
}
else {
params.alert = 0;
}
}
else {
console.log("Required Parameters for Geofence Calculation Not Provided");
return {error: "Required Parameters for Geofence Calculation Not Provided"}
}
return params;
}
function degrees_to_radians(degrees)
{
var pi = Math.PI;
return degrees * (pi/180);
}
