No idea if this would suit you, or if it's technically what you need, but some of the DOD cameras (I only had the LS430W onhand) mention 5X GPS speed (not satellite acquiring, but ongoing refresh rate). If I were to guess, the iTronics cameras I had updated the GPS tracking at about 1Hz (once a second). The LS430W seemed to do it several times per second. So it might just be at 5Hz (times per second).
I doubt you'll get a better GPS unit on a dashcam, as of today. Perhaps with military grade equipment you can go up to 10Hz or 15Hz, but certainly not with $200, and not on a dashcam.
Also bare in mind that GPS has a margin of about 7-8 meters. The highest grade civilian GPS systems go up to about 3m. The military can go to millimetres.
Source: Used to own an airsoft shop/store. We carried different military equipment replicas as well as genuine equipment used by military forces around the world. Including GPS units, communication gear and night vision scopes and goggles.