I've faced the same problem and tried many ways. At last I've came up with a solution - to take angle between previous location point and present location point and I've used an UIImageView instead of GMSMarker.
//in location update method
CGPoint anglepoint = [myMapView.projection pointForCoordinate:currLocation.coordinate];
CGFloat angle = [self getAngle:anglepoint];
if(!isnan(angle)){
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.8f];
sampleImgView.transform = CGAffineTransformMakeRotation(angle);
[sampleImgView setCenter:[myMapView.projection pointForCoordinate:CLLocationCoordinate2DMake(currLocation.coordinate.latitude, currLocation.coordinate.longitude)]];
[UIView commitAnimations];
prevCurrLocation = currLocation;
}
-(CGFloat) getAngle: (CGPoint) touchedPoints
{
CGPoint previousLocationPoint = [myMapView.projection pointForCoordinate:prevCurrLocation.coordinate];
CGFloat x1 = previousLocationPoint.x;
CGFloat y1 = previousLocationPoint.y;
CGFloat x2 = touchedPoints.x;
CGFloat y2 = touchedPoints.y;
CGFloat x3 = x1;
CGFloat y3 = y2;
CGFloat oppSide = sqrtf(((x2-x3)*(x2-x3)) + ((y2-y3)*(y2-y3)));
CGFloat adjSide = sqrtf(((x1-x3)*(x1-x3)) + ((y1-y3)*(y1-y3)));
CGFloat angle = atanf(oppSide/adjSide);
// Quadrant Identifiaction
if(x2 < previousLocationPoint.x)
{
angle = 0-angle;
}
if(y2 > previousLocationPoint.y)
{
angle = M_PI/2 + (M_PI/2 -angle);
}
return angle;
}
Use this for animation:
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.5f];
sampleImgView.transform = CGAffineTransformMakeRotation(angle);
[sampleImgView setCenter:[myMapView.projection pointForCoordinate:CLLocationCoordinate2DMake(currLocation.coordinate.latitude, currLocation.coordinate.longitude)]];
[UIView commitAnimations];
Here is the sample Imageview:
sampleImgView = [[UIImageView alloc]init];
sampleImgView.center = myMapView.center;
sampleImgView.frame = CGRectMake(0,0, 25, 50);
sampleImgView.backgroundColor = [UIColor clearColor];
[myMapView addSubview:sampleImgView];
Hope this helps.