Compare photo location to record location

This example demonstrates how to compare the geotagged location of an attached photo with the location of the record to alert the user if there may be an issue.

// source: https://www.geodatasource.com/developers/javascript
function findDistance(lat1, lon1, lat2, lon2, unit) {
  var radlat1 = Math.PI * lat1 / 180;
  var radlat2 = Math.PI * lat2 / 180;
  var theta = lon1 - lon2;
  var radtheta = Math.PI * theta / 180;
  var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
  dist = Math.acos(dist);
  dist = dist * 180 / Math.PI;
  dist = dist * 60 * 1.1515;
  if (unit == "K") {
    dist = dist * 1.609344;
  }
  if (unit == "N") {
    dist = dist * 0.8684;
  }
  return dist;
}

function validateDistance(event) {
  if (event.value.latitude && event.value.longitude) {
    var kilometers = findDistance(event.value.latitude, event.value.longitude, LATITUDE(), LONGITUDE(), 'K');
    var meters = Math.round(kilometers * 1000);
    if (meters > 20) {
      ALERT('This photo is over 20 meters from the record location. (' + meters + ' meters)');
    }
  }
}

ON('load-record', function(event) {
  // loop through the photo fields
  DATANAMES('PhotoField').forEach(function(dataName) {
    // listen for add-photo event
    ON('add-photo', dataName, validateDistance);
  });
});