[Maik]

Today, while driving on RT 95 in Foxboro, MA (major highway) in a driving rain/sleet storm, the navi kept getting lost. It kept recalculating and finally saying that I was on a non digitized road. This was the first time I have encountered this problem and I would attribute it to the thick cloud cover and precipitation.

Has anyone else encountered this?

 

[ifeldman]

I was using my Nav in downtown Los Angeles tonight and the Nav was recalculating for 10 minutes continuously. I wanted to take a different route home but the Nav was so confused, I gave up on it and took my normal way home. It wasnt raining or thick clouds. It thought I kept driving off the road and actually had me in a lake off the road. It was more than 200 meters away.

The satellite indicator in the upper left of the screen should indicate if rain or sky conditions or anything is blocking the satellites. In my case, all was green. Unfortunately, I was driving where multiple freeways meet and the Nav was more confused than I was. I would think that if there was any place in the whole Nav database that should have been correct, it should be downtown Los Angeles.

 

[Pauls MDX]

Today, while driving on RT 95 in Foxboro, MA (major highway) in a driving rain/sleet storm, the navi kept getting lost. It kept recalculating and finally saying that I was on a non digitized road. This was the first time I have encountered this problem and I would attribute it to the thick cloud cover and precipitation.

Has anyone else encountered this?

There is a signal meter on the upper left hand side. This can happen if the computer looses touch with the different satelites it uses. Wheather will definitely affect it. Usually if it gets a good connection then looses it the computer can still go forward a while without a connection to the satelite again. Remember it's a computer and they sometimes have quirks. It is normal and nothing to worry about as long as you are not having the problem in clear wheather also. Atmospheric conditions can also come into play, just like your satellite television jams once in a while so does the navagation unit.

 

[megabuck2]

Hi All,
Just came back from South Lake Tahoe and believe it or not it was snowing pretty hard at the summit on Monday. Nav system never lost touch with the sat. Gotta remind you that at the summit, the road is in a "valley" and with storm clouds and snow, I thought the nav will get really confused...but nope, it worked marvelously.

Mike

 

[dmyles]

There have been a couple of times where in very cloudy conditions, the Nav thought I wasn't on the digitized road and kept recalculating. I didn't check the satellite indicator but just assumed the satellites lost me because of the dense cloud cover.

However yesterday in driving to Syracuse, at one point the system totally lost track of where I was and thought I was on a side road instead of the highway. It was perfectly clear out. It straightened itself out after about 1/2 mile. I chalked it up to a quirk. But then on the way home, in the exact same spot, it did the same thing. I was wondering if there are specific areas where there are just "black-outs" or something due to the placement of the satellites. Kinda how there are specific areas where you can predict your cellular call will be dropped due to where the towers are.

 

[mcclendons]

GPS uses a fairly low level "L Band" frequency to communicate. No different that any radio, it can have interference or jamming. Also, GPS can be affected by atmospherics---some rain and the like but even more so an effect called "scintillation". Quite possible you are getting a localized “jamming” in that area, but could be an atmospheric effect. I have not seen allot of atmospheric variances myself, but they are clearly there---and even happen on the brightest sunny days.

Not much a normal user can do to rid themselves of these issues. Some high end and military receivers are capable of resolving the issue (as the Taliban can attest!)

 

[roadrunner]

GPS Error

The error in GPS position is relatively small but finite. According to the USAF people who run the system- it SHOULD be within 5.87 METERS 95% of the time. That is certainly large enough to make errors common in closely located streets such as in a city, intersections or service roads. In fact the ONLY reason that the system usually shows you on a road rather than in the grass is that the system has a logic function to ASSUME you are on a road. Drive on the shoulders some time and you will see that it well keep you on the road.
I have found a few particular spots where the error is constant which probably means there is an error in the map since GPS error should be random. There are two places in my town where the NAV always gets it wrong. In one case the road has been physically moved during widening and since the current data release. This puts me off far enough that the system usually jumps me over to the service road. The other is where there is a long exit ramp parallel to the main road. NAV ALWAYS assumes that I'm taking the exit so that is probably a map error since the GPS should guess right at least half the time.
I found a great site with a LOT of information on GPS ERROR . It gives a simple method to measure a system's error.
It also gives a list of the things that contribute to the error:
Ionosphere error (- dual freqency correction - IGS ionosphere model correction - broadcast (Klobuchar) model correction
- no correction)
Satellite clock error (- IGS clock corrections - broadcast clock corrections - broadcast group delay correction )
Orbit error (- IGS/NGS precise (post-processing) orbits - IGS/NGS precise predicted orbits - broadcast orbits )
Troposphere error (- FSL/MAPS troposphere models - measured surface data - generic seasonal model (Herring) - no correction)
Multipath error (- L1 - L2 - antenna and site characteristics )
Receiver errors (- C/A and L1 code range - codeless L2 pseudorange (e.g. cross correlation) - interchannel bias )
Geometric effects (- DOP's -- PDOP, HDOP, VDOP, TDOP - positional effects (high vs. low latitudes) - accuracy + horizontal position + ellipsoidal height + time )
Robust processing effects (adjustment) (- outlier detection - weighting strategies - alternative norm processing )
Now I'm surprised it EVER gets it right

 

[roadrunner]

PS - Solar Activity

You may also note a somewhat greater than normal GPS error as we are currently in a very active time for solar activity which does impact satellite communications including GPS
Meep Meep

 

[weth]

That is real interesting and hopefully explains the problems I had yesterday. The Navi would not/ could not lock onto even 1 satellite. This was for a 1/2 drive home. Clear blue sky in San Diego. I was getting ready to take it into the dealer, drove about 2 hours later, and it worked perfectly and has since then.

Interesting when it doesn't lock, the internal gyro and speed sensors try to guess where you are. As you can imagine, it gets its bearings off. I wish I had my digital camera with me, as the Navi showed me driving right down the runway at San Diego's Lindburgh field.

Thanks for the satellite info, I feel better about the Navi again.


2002 Mahoganny Touring with Navi

 

[DaleB]

Good thing YOU knew were you were, hate to have it think you are on Pacific Highway as a 747 was taxing towards you.

 

[weth]

If the 747 is coming toward me on PCH - should I give him the right of way? I am looking in my DMV book now, can't find the rule on that one????

 

[DaleB]

I think that falls under 'Survival' and where to take your laundry afterwards

 

[ghost]

For those of you experiencing techical difficulty, we're in the midst of a pretty decent magnetic shock wave that started May 23. Check out http://www.spaceweather.com for details.

Pretty good reason why a lot of you have suddenly gone "off-road" the past couple days!

(Post-post edit - oops, see Roadrunner already out-geeked me on this one! My bad...)

 

[vicpai]

Errors in the database will cause this.....

However yesterday in driving to Syracuse, at one point the system totally lost track of where I was and thought I was on a side road instead of the highway. It was perfectly clear out. It straightened itself out after about 1/2 mile. I chalked it up to a quirk. But then on the way home, in the exact same spot, it did the same thing

The Kenwood KNA-DV2100 DVD Navigation system (exact same thing - made by Denso - as the Lexus units) I've installed in my 2003 Corolla has exceptional accuracy in terms of locating me on the globe.....however there are a lot of inaccuracies in the database. The fact that the satellite indicator shows reception of a very strong signal while this is happening as well as these errors seem to always happen in the EXACT SAME LOCATIONS lead me to this conclusion. Another factor I observed helped reinforce this observation: I was driving from Los Angeles to Lompoc (168 mile journey each way) and when I reached hwy 1 (SR-1) for about a couple of miles IN BOTH DIRECTIONS (when going to and coming back from) in the EXACT SAME LOCATION the Nav put me on a parallel highway......now the interesting thing is the parallel highway (major road) was a good distance from the one I was travelling on (certainly not in visual range and therefore certainly not CLOSE ENOUGH for satellite error AND DEFINITELY NOT WITH 7 satellites being received!!!!!!!!!!).......after this episode, I've noticed several more such database "mess-ups"

No matter how accurate the GPS/Inertial reference system of the Navi unit is, it only locates by means of Latitude/Longitude coordinates. Now if mistakes are made while assigning coordinates to streets, by either NAVTECH or possibly by the software guys at Acura/Alpine or Lexus/Denso while formatting the Navtech data to their systems, it will result in an "erroneous representation" on the map!!!

 

[tigmd99]

Hey all,

Does tinting the front windows affect the navigation system???? I have heard this but i am not sure. If it is true, then that just plain stinks! :3:

Thanks.

 

[Pauls MDX]

Hey all,

Does tinting the front windows affect the navigation system???? I have heard this but i am not sure. If it is true, then that just plain stinks! :3:

Thanks.

No not at all, I couldn't see how it would affect the navi because the antenna is on the outside of vehicle. If anything it will give your navi screen a longer life due to less direct sunlight on the screen, cooler interior, and less UV light which is always bad for screens and leather seats and dash boards!

 

[DaleB]

I thought the antenna was between the dash and the front winshield, but still works just fine.

 

[Pauls MDX]

I thought the antenna was between the dash and the front winshield, but still works just fine.

I've never heard of that but it could be true I will try to get some more info on the antenna for the nav from acura directly.

 

[mcclendons]

In an MDX, tinting windows will NOT affect GPS. The antenna on an MDX is on the roof, in the radio antenna.

On other cars, it depends on where th GPS antenna is placed and what type of tint. If the tint has any metal, which some do, it will cause signal loss

 

[DaleB]

The antenna is just above the Navigation unit, up under the center dash.
Reference : page 22-354, of the shop manual. Surprised me too.