B4J Question Calculate distance between two latitude-longitude points?

[suciwulans]

How do I calculate the distance between two points specified by latitude and longitude?
For clarification, I'd like the distance in kilometers; the points use the WGS84 system and I'd like to understand the relative accuracies of the approaches available.

 

[Erel]

You can use the Geodesic class to convert to UTM and then calculate the distance: https://www.b4x.com/android/forum/t...onvert-lat-lon-utm-coordinates.30702/#content

Another option: http://www.movable-type.co.uk/scripts/latlong.html

 

[Philip Prins]

Hello Erel,

Can you give an example to calculate distance between to Lat Lng points in B4J , i use 51.4000 and 4.32432 As Lat and Lon

Tnx
Philip

 

[Jmu5667]

You can covert the java code to b4j, it just the formula you need.

/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*:: :*/
/*:: This routine calculates the distance between two points (given the :*/
/*:: latitude/longitude of those points). It is being used to calculate :*/
/*:: the distance between two locations using GeoDataSource (TM) prodducts :*/
/*:: :*/
/*:: Definitions: :*/
/*:: South latitudes are negative, east longitudes are positive :*/
/*:: :*/
/*:: Passed to function: :*/
/*:: lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees) :*/
/*:: lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees) :*/
/*:: unit = the unit you desire for results :*/
/*:: where: 'M' is statute miles (default) :*/
/*:: 'K' is kilometers :*/
/*:: 'N' is nautical miles :*/
/*:: Worldwide cities and other features databases with latitude longitude :*/
/*:: are available at http://www.geodatasource.com :*/
/*:: :*/
/*:: For enquiries, please contact [email protected] :*/
/*:: :*/
/*:: Official Web site: http://www.geodatasource.com :*/
/*:: :*/
/*:: GeoDataSource.com (C) All Rights Reserved 2015 :*/
/*:: :*/
/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/

import java.util.*;
import java.lang.*;
import java.io.*;

class DistanceCalculator
{
public static void main (String[] args) throws java.lang.Exception
{
System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "M") + " Miles\n");
System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "K") + " Kilometers\n");
System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "N") + " Nautical Miles\n");
}

private static double distance(double lat1, double lon1, double lat2, double lon2, String unit) {
double theta = lon1 - lon2;
double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
dist = Math.acos(dist);
dist = rad2deg(dist);
dist = dist * 60 * 1.1515;
if (unit == "K") {
dist = dist * 1.609344;
} else if (unit == "N") {
dist = dist * 0.8684;
}

return (dist);
}

/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*:: This function converts decimal degrees to radians :*/
/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
private static double deg2rad(double deg) {
return (deg * Math.PI / 180.0);
}

/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*:: This function converts radians to decimal degrees :*/
/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
private static double rad2deg(double rad) {
return (rad * 180 / Math.PI);
}
}

 

[klaus]

In B4x:

Dim Lat1 As Double, Long1 As Double, Lat2 As Double, Long2 As Double
Dim EarthRadius, Angle, Distance As Double
EarthRadius = 6378.137 ' WGS -84 kilometers?

lat1 = txtlatdeg.Text
lat2 = txtlatdeg2.Text
long1 = txtlondeg.Text
long2 = txtlondeg2.Text

Angle = ACos(SinD(Lat1) * SinD(Lat2) + CosD(Lat1) * CosD(Lat2) * CosD(Long2 - Long1))
Distance = EarthRadius * Angle
txtdistance = Distance

It's not as accurate as the DistanceTo method in the GPS libraries. But, depending on your needs, it may be OK.
You may have look HERE, I copied the equations from there.

 

[Philip Prins]

Tnx Klaus