Google Maps SDK, iOS, how to calculate difference in camera movement - ios

Question

I am using Google maps for iOS. Everytime the user pans left or right I reload some data based on new position using this method
- (void)mapView:(GMSMapView *)mapView idleAtCameraPosition:(GMSCameraPosition *)position {
Now I am trying to find a way to calculate that if the user moved a little bit in the same view, and the change was not drastic and it does not warrant another data load, then do not load it. To that End I created a variable called mostRecentCoord that I maintain on load that holds initial location
- (void)mapView:(GMSMapView *)mapView idleAtCameraPosition:(GMSCameraPosition *)position
{
//Here mostRecentCoord is self descriptive, latest entry before this move occured.
if(position.target.latitude == mostRecentCoord.latitude && position.target.longitude ==
mostRecentCoord.longitude) {
return;
}
I thought that I can put a limit on the change in lngtitude or latitude , and based on that decide whether to load new data or not, but then I have to take into account zoom level, scope of coverage.
Anyone has ideas on this? would appreciate it

Answer 1

Here's one idea:
When you do your data fetch, pad the bounds of the visible region on all sides by some amount (eg by 20%).
Then when the view moves, if the new visible region is wholly contained inside your padded region, you don't need to reload the data. If some of the new region is outside, you need to reload.

Answer 2

idleAtCameraPosition is called at every time the camera has ended it's view changes.
lat, and lng is your movement until the user stops to pan (..changing the camera). You can convert that to pixels and vice versa using: CGPoint point = [map.projection pointForCoordinate:coordinates];
GMSCameraPosition *lastCameraPosition;
- (void)mapView:(GMSMapView *)pMapView didChangeCameraPosition:(GMSCameraPosition *)position {
if (lastCameraPosition == nil) lastCameraPosition = position;
// Algebra :) substract coordinates with the difference of camera changes
double lat = position.target.latitude - lastCameraPosition.target.latitude;
double lng = position.target.longitude - lastCameraPosition.target.longitude;
}
dont forget to:
- (void)mapView:(GMSMapView *)mapView idleAtCameraPosition:(GMSCameraPosition *)position {
lastCameraPosition = nil;
}