给定随机纬度/经度，从给定隐含行进方向的坐标列表中找到最接近的坐标（纬度/经度）

Question

Need to write below function to calculate distance given 3 inputs:

1. List of stops with coordinates, which also implies the direction of travelling. More like a polygon or which would form the closed loop.
2. Random co-ordinate around the loop.
3. One of the co-ordinate from the list given in point 1.

Need to find the distance between 2 and 3, keeping the direction of the loop in mind.

PS, More like how Google is finding distance given two points given a route. But cant use Google APIs.

Answer 1

Here you can find formulas and JS code to get distance between coordinates

JavaScript: 
var R = 6371e3; // metres
var φ1 = lat1.toRadians();
var φ2 = lat2.toRadians();
var Δφ = (lat2-lat1).toRadians();
var Δλ = (lon2-lon1).toRadians();

var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
        Math.cos(φ1) * Math.cos(φ2) *
        Math.sin(Δλ/2) * Math.sin(Δλ/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));

var d = R * c;

As far as I understand, you have to check distances between point and all stop nodes in order.

The smallest sum of distances of PS[i] and PS[i+1] reveals the most close segment to that point (does not work always - for example, for self-intersecting paths etc)