Cross comparison of objects within an object

Question

I want to cross compare multiple objects containing location data (latitude, longitude) for the distance between them. The goal is to calculate the farthest two locations from a bunch of locations. I already know how to calculate the distance between two locations but what to do if you have multiple locations?

function FarthestDistance(points) {
// here this function should cross compare all objects within 'points' to calculate which two locations have the furthest distance between them
// the function should calculate the distance between each point in a recursive manner and return the two farthest points back
}

var obj = {{lat1,lon1},{lat2,lon2},{lat3,lon3},{lat4,lon4}};
FarthestDistance(obj);

Hope it is clear now. Thanks.

Hi looks like you need some help. Can you please provide input and expected output examples. Also it is helpful to show what you have tried so far. — Josh Adams, Apr 30 '18 at 12:56
First, make it `var obj = [{....}]. Then: A loop. Keep track of distances between obj1 and obj2. Then distance between obj1 and obj3. Then between obj1 and obj4. Next, keep track of distance between obj2 and obj3, etc. By keep track I mean which distance is greatest. — Matt, Apr 30 '18 at 13:57

score 0 · Accepted Answer · answered May 01 '18 at 09:12

Alright, so this is for a Magic Mirror module I am making. Its a wrapper for the Traccar Service to be deployed on magic mirror. I needed to calculate the farthest two points on the map from an object containing multiple locations of each registered user. Then once I have the farthest two points on the map, I could calculate the middle point between them to set it as center of the map. Now I am working on the zooming of the map to include all the markers on the map.. anyways, for the problem I explained here the solution was found after little bit of research. Here it goes.

function toRadians (deg){ // Helper function
    return deg * (Math.PI/180);
}

function toDegrees (rad){ // Helper function
    return rad * (180/Math.PI);
}

function distance (obj){ // Helper function from https://www.movable-type.co.uk/scripts/latlong.html | http://mathforum.org/library/drmath/view/51822.html
    var R = 6371e3; // metres
    var φ1 = obj[0][0];
    var φ2 = obj[1][0];
    var Δφ = obj[1][0]-obj[0][0];
    var Δλ = obj[1][1]-obj[0][1];

    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));
    return (R * c);
}

function midPoints(obj){ // Helper functions (which I modified for the specifications) from https://stackoverflow.com/questions/477591/algorithm-to-find-two-points-furthest-away-from-each-other | https://www.movable-type.co.uk/scripts/latlong.html | http://mathforum.org/library/drmath/view/51822.html
    var self = this;
    var solution = {"start": [], "end": [], "distance": 0};
    for (i = 0; i < obj.length; i++) { 
        for (j = i+1; j < obj.length; j++) {
            var newpoint = [
                [
                    self.toRadians(obj[i][0]),
                    self.toRadians(obj[i][1])
                ],
                [
                    self.toRadians(obj[j][0]),
                    self.toRadians(obj[j][1])
                ]
            ];
            var distance = self.distance(newpoint);
            if (distance > solution.distance){
                solution = {"start": [obj[i][0],obj[i][1]], "end": [obj[j][0],obj[j][1]], "distance": distance}
            }
        }
    }
    var Bx = Math.cos(solution.end[0]) * Math.cos(solution.end[1]-solution.start[1]);
    var By = Math.cos(solution.end[0]) * Math.sin(solution.end[1]-solution.start[1]);
    var latMid = Math.atan2(Math.sin(solution.start[0]) + Math.sin(solution.end[0]),Math.sqrt((Math.cos(solution.start[0])+Bx)*(Math.cos(solution.start[0])+Bx) + By*By ) );
    var lonMid = solution.start[1] + Math.atan2(By, Math.cos(solution.start[0]) + Bx);
    return {"lat": self.toDegrees(latMid), "lon": self.toDegrees(lonMid), "distance": solution.distance};
}

Cross comparison of objects within an object

1 Answers1