Optrix VideoPro is good but where it lets itself down is in laptime recording (I just time off the video anyway). If you want a dedicated lap time recorder that also gives video as well try Harry's Lap Timer. Its more expensive and will only output one lap at a time Vs a continual video from Optrix VideoPro. They are both made by the same guy.
I would imagine you new Internet but surely the better your signal the more accurate it is? Sort of like crapnav when you lose gps and it guesses where you are