DMZ

Age 2½ months, 1900 miles, VIN 435xx.

More and more often lately, the NAV system misrepresents my actual location.
You New Yawkiz out there in the audience will understand the streets in question.

Some Examples:

- Last week, I was heading west on East 72nd St. towards Central Park. Even within a block of 5th Ave, the system showed me to be on 2nd Ave heading south. Made a right onto 59th St. off of 5th....system showed me to be on 47th St.
- Yesterday, I was on E 79th St heading towards the FDR Drive and the system showed I was on E. 67th St. When I got onto the FDR south, the system showed me going south on 1st Ave! Physically impossible as 1st Ave runs north. It finally straightened itself out when I got off the 23rd St exit and onto 25th St.

This problem didn't start rearing its ugly head until a few weeks ago. Sometimes it'll straighten itself out after a while, and other times I have to shut the car off, restart, and then sometimes it will fix itself, and sometimes it won't.



I know, I know, time to take it in to be checked.
.
.
.

rets

Got some initial questions to you. Did you just get out of the basement garage around those neighborhoods? Were you doing the street-parking in front/north of the tall buildings?

You seemed to get Navi problems in latitudinal (west-east) streets, which means tons of tall consturction in your south.

Sometimes I will continuingly get some interference by crowded skyscrapers in Manhattan. If my Navi gets messed-up, it will take a few minutes or blocks to make itself adjust/correct after existing those areas of skyful concrete.

0.02



Edit: I seemed to put the wrong info here. GPS satellites isn't above the Equator. They ain't XM's. :o

NightRider

I have had this happen to me 2 or 3 times, and find that if you zoom in a couple steps and then back out, it usually fixes itself. Hopefully it works for you too!

DMZ

Yes of course. I don't have the guts to leave that car on the streets overnight in Manhattan, then wear and tear it by driving around looking for parking.

No

As of yesterday, I began getting them on the FDR, a north-south street with stretches NOT next to tall buildings, which thanks to the speed and performance of my TL, I now leap with a single bound.

These issues didn't exist AT ALL up until a few weeks ago. Now, the more time goes on, the more and more this is becoming persistent, even on streets where it didn't happen before. That's why Im getting concerned.

Jss1

Why not go into the GPS satellite position screen before you leave and see how many satellites you are picking up. I think you need at least 3 or 4 to get an accurate reading.

DMZ

What's the button pressing sequence ?

rets

Good one... I was thinking of checking this out, too... sorry, a belated advice.

That's the best way to know if those tall buildings have been blocking you.



Also, you often visited those areas in the past and you had no problems at all with your Navi, right?

Jss1

Map menu cancel all at the same time for 5 seconds I think. Then touch top right I think for satellite location.

DMZ

If you mean 'had' no problems with those spots in the past, you're right, not until recently, and not consistently.

mikekit

Problems with placing your location on the map are normally not caused by the GPS receiver but the base map. Ever since they turned off SA several years ago, most modern GPS units can position with 10 feet or so if they have adequate satellite reception. Creating an accurate street map of the whole United States and cramming it onto a single DVD is a daunting task which is why some parts of it are approximate. Road construction and route changes don’t help this problem.

The GPS position error combined with the map inaccuracies and the NAVI feature that “snaps” the cursor to the nearest road can make your GPS think you’re on the road next to the one your TL is actually on.

I don’t have the owner’s manual in front of me be I remember seeing a calibration feature with the TL NAVI that lets you index your location to the base map. This might help your situation.

My favorite is when the NAVI tells me to drive off an elevated road onto the crossing road below it. Again, inaccurate or out dated base maps must be causing this. There is an area near my office where it’s always on the wrong road and it takes a mile or two to correct itself when I get on the highway.

It’s not just the NAVI unit in the TL that has these problems. I’ve seen the Garmin and Delorme units behave the same way. I think all the GPS companies get their base maps from the same source.

These are wonderful devices and their software has come a long way over the past few years but they are not perfect.

SiGGy

SA (select availability) has been re-enabled since 9/11 I believe But after looking at those graphs looks like our accuracy is about 10'-36' /w a perfect signal.

A good read.
http://www.schriever.af.mil/GpsSupportCenter/

mikekit

I don’t think SA (Selective Availability) is back on. The chart show at http://www.schriever.af.mil/GpsSupportCenter/ shows a horizontal error less than four meters. When SA was turned on, the horizontal error was 100 meters or less which means you are within a circle 200 meters in diameter. This football field size error would be very noticeable if they had turned it back on. We would be several streets off in a city with SA turned on.

SA was turned off temporarily during the Desert Storm War of 1994 (reportedly, the Department of Defense won’t comment on this) then permanently on May 1st 2000. Before it was turned off, street level navigation by GPS was extremely difficult. I remember when it was turned off it was possible for emergency vehicles to determine which side of the interstate an accident was on before arriving. We’re still at that level of accuracy.

If you’re interested, take a look at http://www.ngs.noaa.gov/FGCS/info/sans_SA/ for more information about SA.

mikekit

I can’t seem to make this key sequence work to see the GPS satellite positions. I also cannot seem to find it in the owner’s manual. Am I missing the obvious? Do you know where this feature is documented?

rets

I don't know where it's written, but this was discovered by 04TLers... you could check out the thread of "Found new features...".

mikekit

It was obvious. Thank you Jss1. Thank you rets.

youngTL

DMZ, I'm 100% sure SA is not on because our GPS at work is accurate to less than 1m! I know for sure because I have the data in .sgy files, and I can plot them on a sitemap and find out where the line was run between boreholes. The first and most important thing to find out is how many satellites you're picking up. Anything less than 4 and you will have problems (unless they're positioned above you). That's antoher thing, the satellites have to be positioned around you, not all on one side or you'll get large error. Another thing that could have happened is the connection could be bad (the wires and antenna) or the GPS antenna damaged. It's unlikely though, but possible. It seems like it posted your basemap displaced by several hundred metres, so the most likely issue is that it's having trouble calibrating. What I would do is go onto a major road that's recognized by the system, with no tall buildings around (get out on the highway), and recalibrate the machine. I don't have an 04 TL so I don't know if you can reset them completely, but if you can, do it.

EggrollXpress61

It happens to me too so I guess its normal

DMZ

I've since discovered that this is much more frequent when I set the compass icon away FROM always pointing North, so which ever way you're going, it's always 'UP' on the Nav screen. Once I touch the compass icon to always point North, this problem rarely shows its head.

rets

I do point North after using "UP" in first 3 months, whatever you call.

I did drive 72/79 three times in past two weeks, and luckily have no issues yet.

fostercw

I've been through it all. Do you have metallic tint on the rear window. If you do, it's causing the problem. It doesn't affect all, but it did mine. Removed the metallic and install non-metallic, and its been fine for over 6 months.

DMZ

No added tint.