location.js

//real time location update 
export function regionFrom(lat, lon, accuracy) {
  const oneDegreeOfLongitudeInMeters = 111.32 * 1000;
  const circumference = (40075 / 360) * 1000;

  const latDelta = accuracy * (1 / (Math.cos(lat) * circumference));
  const lonDelta = (accuracy / oneDegreeOfLongitudeInMeters);

  return {
    latitude: lat,
    longitude: lon,
    latitudeDelta: Math.max(0, latDelta),
    longitudeDelta: Math.max(0, lonDelta)
  };
}


export function getLatLonDiffInMeters(lat1, lon1, lat2, lon2) {
  var R = 6371; //        radius of the earth in km
  var dLat = deg2rad(lat2-lat1); // deg2rad below
  var dLon = deg2rad(lon2-lon1); 
  var a = 
    Math.sin(dLat/2) * Math.sin(dLat/2) +
    Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * 
    Math.sin(dLon/2) * Math.sin(dLon/2)
    ; 
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
  var d = R * c; // distance in km is calculated
  return d * 1000;
}


function deg2rad(deg) {
  return deg * (Math.PI/180)
}