navigator.geolocation.getAccuratePosition

navigator.geolocation.getAccuratePosition

// Sligntly modified to return the best position out of those generated. The original script (https://gist.github.com/510278/)
// only returned the last one. tmpAccuracy was added to check against the current position and set the bestPosition if indeed it is the best.
// 
// navigator.geolocation.getAccuratePosition() is an improved version of navigator.geolocation.getCurrentPosition()
// 
// getAccuratePosition() is designed and tested for iOS.
//
// The problem with getCurrentPosition() is that it returns an inaccurate position even with "enableHighAccuracy" enabled.
// The problem with watchPosition() is that it calls the success handler every second, and it is resource-intensive.
// 
// getAccuratePosition() calls the callback only once, but uses watchLocation() internally to obtain a position that meets your accuracy needs.
// If the timeout is exceeded before a position meeting your accuracy is needed, the best position is returned to the
// success callback, and the error callback does not fire. If you really care about accuracy, you should check it
// yourself in your success callback.
//
// getAccuratePosition() has the same signature as getCurrentPosition() and watchPosition()
//   (see http://dev.w3.org/geo/api/spec-source.html#get-current-position)
// BUT allows specification of opts.accuracy, which is treated as a minium required accuracy (in meters)
// If no accuracy is specified, it defaults to 1000m if enableHighAccuracy=false, else 50m.

navigator.geolocation.getAccuratePosition = function(successF, errorF, opts)
{  
    opts.accuracy = opts.accuracy || (opts.enableHighAccuracy ? 50 : 1000);
    opts.timeout = opts.timeout || 10;
    

    var watcher;
    var bestPosition = {};
    var initialTimeMS = (new Date()).getTime();
    var tmpAccuracy = 99999;
   	
    var mySuccessF = function(position) {
        //console.log('watchPosition update: ' + $.toJSON(position));
        console.log('watchPosition update: ' + JSON.stringify(position));
        
		// Get the best position out of any of those generated
    	if (position.coords.accuracy <= tmpAccuracy)
    	{
    		tmpAccuracy = position.coords.accuracy;
    		bestPosition = position;
    	}
    	
        if (position.coords.accuracy <= opts.accuracy || ((new Date()).getTime() - initialTimeMS) > opts.timeout)
        {
        	
            navigator.geolocation.clearWatch(watcher);
            successF(bestPosition);
        }
    };
    var myErrorF = function(error) {
        navigator.geolocation.clearWatch(watcher);     
        errorF(error);
    };
    watcher = navigator.geolocation.watchPosition(mySuccessF, myErrorF, opts);
    
};