Many people get hung up on the number of satellites the gps is receiving. In truth all you need is three to provide a location (four for altitude). Time, very accurate time (thus the need for atomic clocks) is needed to insure that when a measurement is taken from the three satellites it is at the exact same time. This creates a triangulation that can now calculate your location.
The fact that all of the GPS Satellites are in constant motion means that the triangle on which the accuracy depends is constantly changing.
The ideal configuration for the three satellites being used is 20° above the horizon and spaced 120° apart, although this rarely happens and if so only for a short period of time. Many hand held GPS receivers will show you the position of all the satellites the receiver is collecting data from and on a separate page it will show the strength of the satellites (it will also give the # of the individual satellites). Some units will give you estimated accuracy in feet.
This is where the movement you are seeing comes in. As the satellites orbit the earth the shape and size of that triangle is constantly changing and further from the ideal spacing mentioned above the less accurate the calculation.
This is a layman's explanation of GPS positioning and it much more complicated than this as I'm sure Alan and others will point out.
Bottom line if it bothers you don't zoom in so close and you won't even notice it. If it still bothers you get a new hobbie because all the calibration in the world on your Mavic (or any other GPS device) is not going to change it.
