For those with the Navigation systems, have you noticed that
the red arrow seems to fall behind a little?

Perfect example is at an intersection. Once I drive thought the
intersection and quickly look at my screen, I can clearly see the arrow
approaching the intersection, even though I have passed it.

Even On turns on local streets. I have already completed the turn and then the arrow follows along... but is two (2) seconds behind.

Is this normal?

 

it's normal. Normally it's more pronounced at larger areas (so the closest zoom view isn't as bad as 5-mile, etc.).

you can manually adjust it forward if you wish, but I've found making a couple of turns helps with positioning.

 

The lag time is about 50 meters. So its normal. It should tell you when to turn or when you've reached your destination. There also exist the possibility, very slight possibility, that at the very time you are suppose to get a warning like "destination ahead," the satellites becomes "overextended" causing lag time. The 24 (am i correct?) satellites that Acura uses for their GPS is also shared by other companies (not necessarily for NAVI).

 

how do you position it? i see that you can make it so that if the car isnt facing the exact way, then you can turn the arrow, but not adjust it to go forward

 

Hi mastertl -- The simultaneous usage by many different receivers does not have any effect on the GPS constellation or the satellite output. The sats send a specific sequence of of data that the receiver correlates on and then determines the distance from the sats. The GPS sats have no idea how many, if any, receivers are listening.

I've been thinking about the lag some myself. I used to work on aircraft navigation systems that blended GPS, INS, nav radio, airspeed, etc. to get an optimal postion. At first I found it odd that when you sit at an intersection that you don't seem to eventually creep up to the intersection point. I assumed the filters in the nav system would take the long term stable GPS position and move you to the intersection. Now, I'm thinking that they may have given more bias to the velocity input from whatever other sensor is used (accelerometer, or perhaps just from the transmission/computer/speedo). It might give more comfort to the driver to see the map fixed when the car stops moving, instead of seeing it creep and move a little. I haven't sat in one spot too long to test this theory -- it's more fun to drive!

 

I park in a 5 story garage (which I think is off GPS coverage). What puzzles me is that after going up 4*360 degrees and then down 4*(-360) degrees, the Navi ends up in a completely wrong orientation and it takes a few minutes for it to correct itself. It must not be using a compass for the orientation, otherwise it shouldn't get accumulation error like this. I wonder why they aren't using a compass; it would have been perfect in this case.

Also, I wonder what affects GPS triangulation frequency that eventually corrects the position. Is there a way to increase the frequency or anything I can do to make it correct itself sooner?

 

loko,
It's not that the garage is "off GPS coverage" it's that the receiver in the car cannot get the signal from the sattelites to properly locate and orient the vehicle. This is common inside structures such as garages and tunnels. Once back in open air the receiver will be able to figure out its location, but this may take a moment.

I wouldn't worry about trying to "correct" it until the Navi system is smart enough to locate and direct you to open parking spaces. Now that would be a nice feature!

 

That's what I meant by "off GPS coverage" - insufficient number of satellites are detected (probably none) inside the garage.

But my complaints are:

1. Why is it getting severely disoriented after a few rotations? If a compass is used, it wouldn't matter if one makes one rotation or a hundred; north is north and there is no accumulation error; Apparently they are not using a compass (why?) or my compass is not working.

2. Why does it take minutes to correct itself? If it notices that I am not following the road but going across, that's a good indication that its idea of where I am is wrong and it should inquire the GPS coordinates ASAP. Instead, its behavior is consistent with it tracing my path and trying to fit it somewhere onto the local map, which requires sufficiently long trace. Either the GPS information it gets is way too imprecise (unlikely) or it inquires very infrequently. If it inquired every 5 seconds instead of every minute or so we wouldn't have this problem in the first place.

 

I find my navi TL on the map position is off by almost a 100 feet. How do I adjust the navi (auto) position? Has anyone tackled that process here? Thanks.

 

maybe you can screw around with it in diagnostics mode. There must be a way. There is something in the programming(must be adjustable) that tells it how often to update. Has anyone called the dealer, they may know how to do it. There must be some effieceincy reason that it updates at that rate too. I dont think its possible to overload the sattalites so I doubt thats why there is a limit. They simply broadcast a constant signal of atomically set time, using this vehicles can triangulate there position. Anyway, I would be interested to know, we are getting an Acura in the next 6 months with navi, and having it be more accurate would be great. The in popmec they said that military is acurate to within 10 feet, and at the time the article was published lexus had the most accurate nav.