CODEWITHSUNDEEP
javageolocationgisgeospatial
ashok
ashok

Reputation: 1268

How to calculate distance between two point over a path

I am having a list of co-ordinates that represent the path, and source and destination coordinates. So, using spatial4j,JTS,GeoTools or any other library how to calculate the distance between two points(source & destination) over a predefined path(list of coordinates).

Below is the sample which I have tried using spatail4j which is a straight line distance. But the same thing how we can achieve over a path I have used spatial4j but using different libraries like JTS,GeoTools etc.,

public static void main(String[] args) {
        SpatialContext ctx = SpatialContext.GEO;
        Point p1= ctx.getShapeFactory().pointXY( 77.610099,12.91502);
        Point p2= ctx.getShapeFactory().pointXY( 77.59038,12.917055);
        System.out.println(ctx.getDistCalc().distance(p1, p2) * DistanceUtils.DEG_TO_KM);
    }
// output: 2.149124512680105

Below are the route/path geopoints:

12.91502 , 77.610099
12.91502 , 77.610092
12.913957 , 77.610069
12.913954 , 77.610033
12.91644 , 77.610048
12.916573 , 77.605512
12.916618 , 77.603053
12.916622 , 77.601803
12.916652 , 77.600092
12.916735 , 77.597653
12.916896 , 77.590946
12.916927 , 77.590242
12.916936 , 77.589467
12.917083 , 77.589466
12.917055 , 77.59038

According to the google map the value should be 2.8Km. Is there any other java library using which we achieve the same thing as the resource for spatial4j is very less.

Upvotes: 1

Views: 1480

Answers (3)

Rodrigo Rodrigues
Rodrigo Rodrigues

Reputation: 8576

Other responses I see here are good, @Luiz's is simple and straightforward, and @8bit's is more precise.

No matter which implementation of them you choose (or even the one you provide in the question itself ctx.getDistCalc().distance), I'd like to give an insight for the problem it seems you're struggling the most: how to apply and accumulate the results of your distance function over the whole list?

IntStream.range(0, path.length)
         .map(i -> i == 0 
                   ? 0.0d 
                   : ctx.getDistCalc().distance(path[i - 1], path[i]))
         .sum()
         * DistanceUtils.DEG_TO_KM;

This assumes path is an array with your points. More info on streams here.

Upvotes: 1

hobyte
hobyte

Reputation: 623

public static void main(String[] args) {
        ArrayList<Point> points = new ArrayList<>();
        points.add(new Point(1, 0));
        points.add(new Point(2, 0));
        points.add(new Point(3, 0));
        
        int distance = 0;
        
        for (int i = 1; i < points.size(); i++) {
            Point smaller = points.get(i-1);
            Point bigger = points.get(i);
            distance += Math.sqrt(Math.pow(bigger.x-smaller.x, 2)+Math.pow(bigger.y-smaller.y, 2));
        }
        System.out.println(distance);
    }

It can work like this. Use Pythagoras for the distance between Point 1 and 2, then Point 2 and 3. At the end add up all those calculated distances.

Upvotes: 2

Luiz Damy
Luiz Damy

Reputation: 234

If you want precision, then you should probably go to Haversine Formula, luckily enough, you can always find a useful solution browsing the web

public static Double getDistance(Double lat1, Double lon1, Double lat2, Double lon2) {
    final int R = 6371; // Earth Radius in km, use 3959 if you want in miles
    Double latDistance = toRad(lat2-lat1);
    Double lonDistance = toRad(lon2-lon1);
    Double a = Math.sin(latDistance / 2) * Math.sin(latDistance / 2) + 
    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * 
    Math.sin(lonDistance / 2) * Math.sin(lonDistance / 2);
    Double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    return R * c;
}

I've actually just adapted this to your use-case.

Upvotes: 2

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