Calculate distance using geolocation in ionic 4 - ionic-framework

Question

I already can get my map and the route between two points, i would like to calculate de distance in km between that points
the code to trace the route
displayDirection(_origin, destin) {
var ref = this;
console.log('DIRECTION');
var directionsService = new google.maps.DirectionsService();
var directionsDisplay = new google.maps.DirectionsRenderer();
directionsDisplay.setMap(ref.map)
directionsService.route({
origin: _origin,
destination: destin,
travelMode: 'DRIVING'
}, (response, status) => {
console.log("Response: " + response + " Status: " + status);
if (status === 'OK') {
directionsDisplay.setDirections(response);
} else {
console.log("Can't set directions due to " + response);
}
});
}
can someone help me?

Answer 1

If you take the response that you receive, there will be an Array of Routes that It will show under the object
response.routes
In your request object, the array will have one or many route objects in it. The route object will have an array of legs breaking down the journey to smaller pieces. Simply Iterate the Legs to find the total distance. You can use the following method to find it for a route.
findRouteDistance(route) {
var total_distance = 0;
var route_legs = route.legs;
for(var i=0; i < route_legs.length; i++) {
total_distance += route_legs[i].distance.value;
}
return total_distance;
}
If you have only 1 route object simply call
findRouteDistance(response.routes[0])
Or iterate over the response.routes object if you have many.

Answer 2

to get the distance between two points
getDistanceFromLatLonInKm(lat1,lon1,lat2,lon2) {
var R = 6371; // Radius of the earth in km
var dLat = this.deg2rad(lat2-lat1); // deg2rad below
var dLon = this.deg2rad(lon2-lon1);
var a =
Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(this.deg2rad(lat1)) * Math.cos(this.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
return d.toFixed(2);
}