My Terrova is only accurate to within about 6-8' of target if there isn't at least a 5 mph wind blowing steady from the same direction. I think MK designed it to be used in steady wind.
After about 15 minutes, the Terrova loses its satellite and has to search for about 30 seconds to find the new one overhead. Not ideal, but still better than pulling an anchor every time you move.
Maybe the new versions of Spotlock are more accurate in mild winds. My next one will be an Ulterra. Pulling up the Terrova is getting harder and harder!