Originally Posted by
Riveting
Speed (avg. and instantaneous) is unimportant anyway, there's too many variables involved that change from ride-to-ride, or hour-to-hour (wind, hill gradient, tire rolling resistance, bike weight, rider weight, clothing aero drag, riding position aero drag, drafting other riders) to make it useful for analysis, except maybe to avoid breaking the speed limit, if that's your thing. Once you come to grips with that, the GPS inaccuracy won't matter to you. If you really care to monitor your performance, I'd recommend getting a torque based power meter, and you'll never look at speed again.
i do use average speed to determine improvement and fitness level. At the beginning of the season, after taking winter off, my average speed for the first week was about 14 MPH. Today riding the same route with an additional 300’ climb thrown is, my average was 19.3. I enjoy competing against others and myself. I know that is not for everyone but I get a certain level of satisfaction by increasing my speed, endurance and distance. But even at 65 I still have a defective gene that is achievement and goal oriented. I do stop and enjoy views and wildlife and to admire the wonder at it all.