0

I'm developing a simple jQuery / Phonegap app and I'm using watchPosition to constantly calculate between the distance current location and some remote place. This works just fine, but this is my issue. I would like to trigger an event (function) when the distance is less than a mile from that location. The way I have it right now it would continue triggering the event as long as the distance is less than a mile. What can I do to "tell" watchPosition to trigger the event only once and continue watching my position?

I included what I consider the relevant part of the code for your reference.

Success portion of watchPosition:

var remoteLat = xx.xxxx;
var remoteLng = xx.xxxx;

function onSuccess(position) {
var myLat = position.coords.latitude;
var myLng = position.coords.longitude;
var distancia = gps_distance(myLat, myLng, remoteLat, remoteLng);

if (distancia < 1) {
    alert('Almost There');
    playSound();
}

}

Distance calculating function:

function gps_distance(lat1, lon1, lat2, lon2) {

var R = 3959; // use 3959 for miles or 6371 for km
var dLat = (lat2 - lat1) * (Math.PI / 180);
var dLon = (lon2 - lon1) * (Math.PI / 180);
var lat1 = lat1 * (Math.PI / 180);
var lat2 = lat2 * (Math.PI / 180);

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;

return d;
}

If more of the code is necessary, please let me know. I also would like to give credit to this question previously asked about calculating distances Link . Thanks!

Community
  • 1
  • 1
cubanGuy
  • 1,226
  • 3
  • 26
  • 48
  • 1
    why do you not use a varibale to make sure your this event will become irrelevant when distance falls below a mile? – Blauharley Apr 03 '15 at 17:40

1 Answers1

2

Just use a flag to track the alert. 

var alerFlag = true;
if (distancia < 1 && alerFlag == true) {
    alert('Almost There');
    playSound();
    alerFlag = false;
}else{
    alerFlag = true; // This is for whenever you go greater than 1 mi
}
Banik
  • 911
  • 6
  • 10