has anybody calibrated/verified the GoPro speedometer/GPS data? Is it accurate? Seems like I see a lot of high speeds from GoPro overlays. Was thinking of getting a GoPro w/ GPS just for this feature

The GoPro won't do fractions of a mph, knt, etc. If you want 35 mph to have to hit 35 or greater. Other GPS units will give you 34.89 for example. The GoPro won't give an average speed over a set distance like other GPS brands. I found the GoPro desktop software had higher resolution than their mobile software for capturing peak speeds. You would need to have a Gopro and another GPS brand onboard and located in the same spot roughly and run some tests. Under the boom mount might cause some satellite blockage. You could ask the same question for a GPS brand against another GPS brand too. There's also phone apps. Somebody needs to wear 4 different kinds and take'em for a spin.

It feels like you're going 40 mph, but my GoPro said nope you're doing 34 mph.

Get one and join the fun.

Here's Ady testing it with his car from another thread.

Ady wrote:

good to know! thanks!