Although the older models of the SRM PC training computer used a speed sensor, the PC8 is outfitted with GPS. Overall, it works really well, is precise and reliable, hover it does take 2-3 minutes to acquire a signal. On top of the GPs, everything you would expect to be in a bicycle computer is there. Data like, power, heart rate, speed etc. are all included, but metrics like Training Peaks TSS® (Training Stress Score®), NP (Normalized Power®), IF® (Intensity Factor®) are also packed in.