Google map getting the range of possible lat and lng from a point with a radius

Question

So I'm trying to find what range of latitude and longitude values I can use when trying to find other points on a map from an origin position based on the radius (e.g. 5km).

Current I'm using the Haversine formula from Calculate distance between two points in google maps V3 to calculate how long 1m is in both latitude and longitude.

var rad = function(x) {
  return x * Math.PI / 180;
};

var getDistance = function(p1, p2) {
  var R = 6378137; // Earth’s mean radius in meter
  var dLat = rad(p2.lat - p1.lat);
  var dLong = rad(p2.lng - p1.lng);
  var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(rad(p1.lat)) * Math.cos(rad(p2.lat)) *
    Math.sin(dLong / 2) * Math.sin(dLong / 2);
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  var d = R * c;
  return d; // returns the distance in meter
}

let origin = {lat: 40, lng: 40}
let p1 = {lat: 41, lng: 40}
let p2 = {lat: 40, lng: 41}

let latDist = getDistance(origin, p1)
let lngDist = getDistance(origin, p2)

console.log(latDist, lngDist);

let lat1m = 1/latDist
let lng1m = 1/lngDist

console.log(lat1m, lng1m)

From this, 1m in latitude is roughly 0.000008983152841195214 and 1m in longitude is roughly 0.000011726734698319366. So 5km would just be 5000 multiplied by each of the points then plus/minus from the origin.

Was there a Google API to get possible ranges or is this the correct method?

@shukshin.ivan because I'm using this along with Google API? — A. L, Apr 06 '18 at 08:38

shukshin.ivan · Answer 1 · 2018-04-06T08:42:11.820

UPD.

I was wrong, you can use google.maps.geometry.spherical.computeDistanceBetween (latLngA, latLngB); to calculate distance between two points. Docs. Just pass LatLng objects.

OLD JS ANSWER.

As for your question, you don't need to use Google API at all. In addition, Google API doesn't provide simple functions, that can be calculated using geometry.

Let me make your code a little simplier. Length of an arc is simply radius * angle in radians. So lat distance is latDist = R * dLat and lng distance is lngDist = R * dLng * Math.cos(rad(origin.lat)). If you calculate distances, smaller than thousand of kilometers, you can assume, that latitude is constant within the area, hence you don't need to use complex formula for that.

var rad = function(x) {
  return x * Math.PI / 180;
};

var R = 6378137; // Earth’s mean radius in meter
let origin = {lat: 40, lng: 40}

let latDist = R * rad(1)
let lngDist = R * rad(1) * Math.cos(rad(origin.lat))

console.log(latDist, lngDist);

let areaRadius = 1000; // in meters

let latitudeRangeDelta = areaRadius / latDist;
let longitudeRangeDelta = areaRadius / lngDist;

console.log('latitude of the area is within range [' + (origin.lat - latitudeRangeDelta) + ', ' + (origin.lat + latitudeRangeDelta) + ']')
console.log('longitude of the area is within range [' + (origin.lng - longitudeRangeDelta) + ', ' + (origin.lng + longitudeRangeDelta) + ']')

I'm saving points on google map, and I need to retrieve certain data whose points fit within the radius. So if I'm trying to get stores within 5km of my position I don't want to retrieve stores that are outside that radius. — A. L, Apr 06 '18 at 08:40
well since I'm trying to query my db, just doing e.g. `(lat > 40 && lat < 41) && (lng > 40 && lng < 41)` will give me a square, which I guess isn't game-breaking, but it might mean that I will have to do a second run with the function `google.maps.geometry.spherical.computeDistanceBetween (latLngA, latLngB);` to check if it's within the radius. — A. L, Apr 06 '18 at 08:47
Right, compare the result of `computeDistanceBetween(center, point)` with area radius. If it is less that radius, it is within the area. — shukshin.ivan, Apr 06 '18 at 08:50
I haven't yet implemented this. It's a good answer, but I'm hoping that the query won't be abysmally long. — A. L, Apr 09 '18 at 10:44

Google map getting the range of possible lat and lng from a point with a radius

1 Answers1