Keep in mind the GPS position information has lag. So at 40mph I wouldn't expect the position to be 100% accurate. It's not like a car GPS where the display and receiver are at the same spot. The drone location has to be transmitted to the receiver and then on to the phone/tablet. I've read the telemetry arriving at the controller is lagging about one half second. This can be made worse when recording 1080p video on the local device.
ps: My
SC has lag, so it's probably also what the user's expectations are.