GPS Distance Calculation - gps

Question

I want to calculate the distance between two GPS locations, each with a latitute value and a longitude value. The calculations should be accurate for short-distance results. eg. < 300m. If I use Google Earth (see coord in my code) , the distance is ~136m.
If I use the solution provided by article: http://www.movable-type.co.uk/scripts/latlong.html (the haversine formula) the result is nothing near that.
used code:
public void GpsCalc(){
double d = getDistance(51.342299,4.371359, 51.342490,4.371997);
Log.e("GpsCalc", String.valueOf(d));
}
public static double getDistance(double lat1, double lng1, double lat2, double lng2){
double R = 6371; // earth’s radius (mean radius = 6,371km)
double dLat = Math.toRadians(lat2-lat1);
double dLon = Math.toRadians(lng2-lng1);
double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
Math.sin(dLon/2) * Math.sin(dLon/2);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
double dr1 = R * c;//in radians
Log.e("getDistance-dr1", String.valueOf(dr1));
return dr1;
}
I'm sure it should be some minor change, but i can't see it.

Answer 1

I have also had trouble with the haversine formula on that page. I know it's not precisely an answer to your question, but I had more success with the law of cosines formula, which gives the same results as Google Earth. In case it helps, it looked like this:
public double getDistance(double lat1, double lon1, double lat2, double lon2) {
double latA = Math.toRadians(lat1);
double lonA = Math.toRadians(lon1);
double latB = Math.toRadians(lat2);
double lonB = Math.toRadians(lon2);
double cosAng = (Math.cos(latA) * Math.cos(latB) * Math.cos(lonB-lonA)) +
(Math.sin(latA) * Math.sin(latB));
double ang = Math.acos(cosAng);
double dist = ang * EARTH_RADIUS;
return dist;
}
EDIT:
I tried your coordinates in Google Maps and Google Earth and in my code, and I'm getting 49m for all of them. Maybe there was never a problem?

Answer 2

A bit late, but two more options
Using Apple Corelocation (49.2733 meters)
CLLocation *currentLocation = [[CLLocation alloc] initWithLatitude:_posGPSCurrent.latitude longitude:_posGPSCurrent.longitude];
CLLocation *location = [[CLLocation alloc] initWithLatitude:_posGPSTarget.latitude longitude:_posGPSTarget.longitude];
// in kilometers
CLLocationDistance distance =[currentLocation distanceFromLocation:location]/1000;
Manual calculation (49.1393 meters)
Include Math library
#include <math.h>
// distance in Kilometers (Haversine)
-(double)distanceFromGPSlat1:(double)tlat1 lon2:(double)tlon1 lat2:(double)tlat2 lon2:(double)tlon2
{
double distance = ((acos(sin(tlat1*M_PI/180)*sin(tlat2*M_PI/180)+cos(tlat1*M_PI/180)*cos(tlat2*M_PI/180)*cos((tlon1-tlon2)*M_PI/180))*180/M_PI)*60*1.1515*1.609344);
return distance;
}
Perhaps I prefer the second method (Manual calculation).