Dog Tail Analogy

Let me 'splain. If you want to know exactly where your dog is, you could put at GPS sensor in the middle of it's body, perhaps near the pancreas. It would give you an average position for your dog, and would be most accurate most of the time. If you put the GPS sensor on the tip of the dog's tail, and used that to estimate where your dog is, you would be nearly wrong much of the time, even if over the long term this would be a good estimate for where your dog has been. More importantly, if you wanted to measure the movement of your dog, the GPS sensor in the middle of the dog's body would…