[Mellow_Labs] was asked to create a GPS speedometer. It seems simple, but of course, the devil is in the details. You can see the process and the result in the video below.

We have to admit that he does things step-by-step. The first step was to test the GPS module’s interface. Then, he tried computing the speed from it and putting the result on a display. However, testing in the field showed that the display was not suitable for outdoor use.

That prompted another version with an OLED screen. Picking the right components is critical. It struck us that you probably need a fast update rate from the GPS, too, but that doesn’t seem to be a problem.

The other issue is, of course, that you have to have a GPS lock for this to work. Inside the urban canyon, you might be better served with a different method. You might think about an accelerometer, but while that’s easy in theory (velocity is the integration of acceleration), in practice, errors and other issues make that a tough way to do it.

The project wraps up with a nice case and some special display modes. We were sorry that the code and STLs were available “on request,” but you’d probably do it differently anyway. This isn’t the first GPS speedometer we’ve seen. Ever wonder how fast your dog is going?