What some new GPS users will discover after a period of lots of use is that different GPS manufacturers have tweaked many of the small details of operation. The basic position fixing operation is cut and dried, but lots of the small details are not. An example is how the receiver treats a fixed position. If you are in a fixed position, how does the receiver really know that it is in a fixed position? If the velocity gets extremely close to 0.0 mph, then that is one indicator. However, even a fixed position will give a "snail crawl" track display due to the small errors of the system. How many feet is it allowed to seemingly crawl before it determines that it is not in a fixed position? Is it one foot, ten feet, or fifty feet? For years I used a receiver that had a Position Averaging Mode. Run it for four hours in one spot, and then it knew precisely where it was (not just about where it was).
Further, few manufacturers specify these kinds of small details for user operation. Those are considered to be trade secrets. Lots of these small techy details fall into the category of "heuristics." That means guesswork or maybe common sense. It would really help some users if the heuristics were spelled out. That way, they could know what the GPS receiver is thinking and guessing, and that could help the user to know when a GPS blunder is happening, and then what to do about it.
If the receiver is a so-called mapping receiver, should the display be forced to be North Up, or should it be Destination Up? What if there is no destination? There are just all kinds of techy details hidden in there, and it becomes great fun to try to unravel the secrets.