It could be because of satellite position. GPS [I believe it still does] relies on signal from 3 satellites to establish it's coordinates. It could have been a situation where one or more of the needed signals were over the horizon and your Dash GPS was not getting coordinate information to do it's internal calculations. Temporary triangulation loss.
On Thu, Jan 9, 2020 at 8:45 PM Craig via Mercedes <mercedes@okiebenz.com> wrote: > Since the BRV's speedometer is recessed in the dash and since it reads > high when it is cold, I have been using our GPS as a speedometer for some > time now. > > Shirley had a dental appointment today so we were in northwest > Albuquerque. After her appointment, I programmed the GPS to find the > quickest way to the Fleet Pride store in downtown Albuquerque and we > were off (you have to be off to do this kind of thing! :-) ). > > As we were driving east on Paseo del Norte, I heard the GPS saying, > "Recalculating!" several times. Then I noticed I was going slower than > the speed limit of 60 mph -- the GPS said 52. I accelerated and noticed > the GPS said 48. I then looked down at the speedometer (it was after > sunset and I had the lights on so the speedometer needle was easy to > see). It said we were going 65! > > I slowed down and push the button on the GPS to return to the map > display. It showed the vehicle about 500' north of the roadway and going > on neighborhood roads instead of on the freeway! When we crossed the Rio > Grande (where there are no neighborhood roads parallel to the freeway!) > it decided we were on the freeway afterall. > > We got off on the left side of the freeway, turned right, and went under > the eastbound lanes and stopped at a stoplight with a clear view of the > sky. I looked at the GPS's map and saw it said we were about 500' west of > our actual location. This continued as we headed south on 2nd street. > > I thought this was rather odd, having never seen anything like this > before. > > It could have been caused by someone transmitting locally on GPS > frequencies, but those are predominantly line-of-sight and we had > travelled a few miles and were on the other side of a freeway > overpass's earth berm. In addition, after a while it started working > correctly again. > > It occurred to me it could have been due to the Department of Defense > turning on Selective Availabilty (which has been off for several years). > > Anyway, I first noticed the wierdness about 1640 MST (2340Z). > > > Craig > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
