Calculating Speed for a navigation app without getSpeed() method

Question

I am developing an app which is more of a time-shift racing between your friends.

I need to calculate speed of a moving vehicle, and I don\'t want to use Locat

Answer 1

I develop MyTrails, an Android mapping and tracking app, and like you I struggled at first with the very crude location APIs Google has seen fit to include in Android.

hasSpeed() is false when the GPS chip doesn't have a good enough fix to compute speed based on dopler effect. Even when it does, I usually don't trust the speed if it's less than 5km/h or thereabouts.

The way I handle speed calculations is by using a crude low-pass filter: I record a trackpoint every second (and a minimum of 5m apart, based on LocationManager.requestLocationUpdates(), and to calculate the recent speed, I go back a few samples to get one that is a sufficient distance apart (but no more than 30s prior), and perform the averaging you're doing.

I'm using Location.distanceBetween() for the actual distance calculation. Beware that it fails on a very small (but unfortunate) number of devices, so the haversine method you have may be a better bet. You may want to check it though, what I have is

/**
 * Gets distance in meters, coordinates in RADIAN
 */
private static double getDistance(double lat1, double lon1, double lat2, double lon2) {
    double R = 6371000; // for haversine use R = 6372.8 km instead of 6371 km
    double dLat = lat2 - lat1;
    double dLon = lon2 - lon1;
    double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
            Math.cos(lat1) * Math.cos(lat2) *
                    Math.sin(dLon / 2) * Math.sin(dLon / 2);
    //double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    return 2 * R * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    // simplify haversine:
    //return 2 * R * 1000 * Math.asin(Math.sqrt(a));
}

(note the 1000 factor)