Get Latitude and longitude center of Google Map

You are doing it right to get the center of the map by using the google maps's func mapView(_ mapView: GMSMapView, didChange position: GMSCameraPosition) delegate.

Take a variable for center coordinates

var centerMapCoordinate:CLLocationCoordinate2D!

Implement this delegate to know the center position.

func mapView(_ mapView: GMSMapView, didChange position: GMSCameraPosition) {    let latitude = mapView.camera.target.latitude    let longitude = mapView.camera.target.longitude    centerMapCoordinate = CLLocationCoordinate2D(latitude: latitude, longitude: longitude)    self.placeMarkerOnCenter(centerMapCoordinate:centerMapCoordinate)}

Function to place a marker on center point

func placeMarkerOnCenter(centerMapCoordinate:CLLocationCoordinate2D) {    let marker = GMSMarker()    marker.position = centerMapCoordinate    marker.map = self.mapView}

In this case you will get a lot of markers. So keep a global hold of marker and check if it is already present, just change the position

var marker:GMSMarker!func placeMarkerOnCenter(centerMapCoordinate:CLLocationCoordinate2D) {    if marker == nil {        marker = GMSMarker()    }    marker.position = centerMapCoordinate    marker.map = self.mapView}