I have the RVND 7710. Only used it about three times. First trip from Tennessee to the Gulf Coast of FL., I programed it for three very well known RV park destinations that I know by heart anyway. Really just wanted to test the accuracy. Two of the three the RVND 7710 would have taken us either past the destination or down a wrong road. I reported the two incorrect points to "Tell Rand", with the EXACT coordinates of the two locations, six months later they still haven't updated the map. I would not trust it as far as I could throw it.
My Verizon cell phone with GPS is much more accurate.