public Target ()
{
Title = "Target";
var paris = new Location {
Latitude = 48.8567,
Longitude = 2.3508
};
pointer = new Pointer (paris);
var updateButton = new Button {
Text = "Update"
};
updateButton.Clicked += UpdateHeading;
arrow = new Image {
Source = ImageSource.FromFile ("Arrow")
};
Content = new StackLayout {
Children = {
arrow,
updateButton
}
};
}
public double BearingTo (Location destination)
{
double p1 = ToRadians (this.Latitude);
double p2 = ToRadians (destination.Latitude);
double l1 = ToRadians (this.Longitude);
double l2 = ToRadians (destination.Longitude);
double y = Math.Sin (l2 - l1) * Math.Cos (p2);
double x = Math.Cos (p1) * Math.Sin (p2)
- Math.Sin (p1) * Math.Cos (p2) * Math.Cos (l2 - l1);
return ToDegrees (Math.Atan2 (y, x));
}
public double DistanceTo (Location destination)
{
// Using "haversine" formula
double R = 6371000.0; // meters, earth's radius
double p1 = ToRadians (this.Latitude);
double p2 = ToRadians (destination.Latitude);
double dp = ToRadians (destination.Latitude - this.Latitude);
double dl = ToRadians (destination.Longitude - this.Longitude);
/*
* var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
* Math.cos(φ1) * Math.cos(φ2) *
* Math.sin(Δλ/2) * Math.sin(Δλ/2);
* var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
* var d = R * c;
*/
double a = Math.Sin (dp / 2) * Math.Sin (dp / 2)
+ Math.Cos (p1) * Math.Cos (p2)
* Math.Sin (dl / 2) * Math.Sin (dl / 2);
double c = 2 * Math.Atan2 (Math.Sqrt (a), Math.Sqrt (1 - a));
return R * c;
}
public void UpdateDeviceLocation (Location deviceLocation)
{
bearingToLocation = deviceLocation.BearingTo (Target);
Distance = deviceLocation.DistanceTo (Target);
}
public Pointer (Location target)
{
Target = target;
lastSunUpdate = DateTime.Now;
}
