Need help trying to create radar for AR app

[mr3cho]

I'm trying to implement a small radar that plots targets based on latitude and longitude coordinates similar to the radar in the Layar AR iPhone app. I have the compass and locationManager working to get the lat/lon, heading and distance between two points. However I'm having trouble plotting the points onto the x-y plane. Could you point me in the right direction(so-to-speak)?

This is the method that I am using to get the heading between two sets of coordinates:

-(float) getHeadingFromCoordinate:(CLLocation*)fromLocation toCoordinate:(CLLocation*)toLocation
{
float flat = fromLocation.coordinate.latitude;
float flon = fromLocation.coordinate.longitude;
float tlat = toLocation.coordinate.latitude;
float tlon = toLocation.coordinate.longitude;

//convert to radians
flat = (M_PI * flat)/180;
flon = (M_PI * flon)/180;
tlat = (M_PI * tlat)/180;
tlon = (M_PI * tlon)/180;

float heading = atan2(sin(tlon-flon)* cos(tlat), cos(flat)*sin(tlat)-sin(flat)*cos(tlat)*cos(tlon-flon));

return heading;
}

This si the method I am using to plot but the results are not correct:

-(void) addTargetIndicatorWithHeading:(float)heading andDistance:(float)distance{
    //draw target indicators
    //need to convert radians and distance to cartesian coordinates
    float radius = 50;
    float x0 = 0.0; 
    float y0 = 0.0;

    //convert heading from radians to degrees
    float angle = heading * (180/M_PI);

    //x-y coordinates
    float x1 = (x0 + radius * sin(angle)); 
    float y1 = (y0 + radius * cos(angle)); 

    TargetIndicator *ti = [[TargetIndicator alloc] initWithFrame:CGRectMake(x1, y1, 5, 5)];
    [self addSubview:ti];
    [ti release];

}

[mr3cho]

Figured it out. Needed to leave the heading as radians and subtract 180 degrees from it. this is the new method:

-(void) addTargetIndicatorWithHeading:(float)heading andDistance:(float)distance{
    //draw target indicators
    //need to convert radians and distance to cartesian coordinates
    float radius = 50;
    float x0 = 50.0; 
    float y0 = 50.0;
    
    //leave in radians and subtract from PI to rotate 180
    float angle = M_PI - heading; 
        
    float x1 = (x0 + radius * sin(angle));   
    float y1 = (y0 + radius * cos(angle)); 
    
    TargetIndicator *ti = [[TargetIndicator alloc] initWithFrame:CGRectMake(x1-2.5, y1-2.5, 5, 5)];
    [self addSubview:ti];
    [ti release];
    
   
}