lepoch

Hi--was looking at the GPS screen in the hidden menu and noted that my lattitude is correct but the longitude was over a degree off. The HDOP was 2.3, was 3D and was getting tracking from 6 satellites. The location on the map is accurate. Is there anyway to force a cold boot on the GPS to fix this? The error has been constant for a week now.

Tanks.

TACOMAN23

Hi there! I am going to assume that you managed to enter the secret diagostic screen on the GEN4 NAVI, through the CRA-NAVI volume screen. I have seen many people enter this screen and touch things that they are no supposed to touch. Buddy, my recommendation is that if your driver's icon is position correctly, based on your geographical location, DO NOT TOUCH or RESET NOTHING ON THAT SCREEN!! The NAVI (receiver) in in 3D mode, which indicates that you have more than 4 GPS satellites tracking and positioning your vehicle. This is a good indication. If you have indicated that you are 1 degree off on your longitude, it probably is okay. I am also going to assume that you are comparing your results with another hand held device. Most likely, the CAR-NAVI receiver reading is more correct, than your hand held device. If you have another friend with a Lexus NAVI, try to park the vehicles side by side and compare the latitude and longitude results. If both vehicles are relatively the same, leave the NAVI alone and try not to enter the secret menu often.

lepoch

Um, in a word, no. I know the geocords of my house. The GPS in the GX is wrong. Thanks.

BobsGX

I have the same problem with my 06 GX. My 05 GX had the same problem also. I was hoping when I got the 06 that Navteq would have fixed the discrepency because the 06 GX has the latest nav DVD disc that just got released earlier this month. But, no they didn't. I had an 05 Dodge Magnum RT prior to the 06 GX and when I got the car in 10/04, it had the older nav disc and my street wasn't even on the nav disc. About a month after I boght the Magnum, Dodge released a new version of the nav disc andmy dealer gave me the disc. Sure enough, it had my street on it and had me correctly at my house. The current as well as the older version of the nav disc in the GX has me at house #143 when in fact my house # is121.
Since both D/C (Daimler/Chrysler) and Toyota/Lexus has the mapping software done by Navteq, I just don't understand why the Toyota/Lexus version is off. I emailed Navteq, and they gave me a long song and dance excuse which didn't make any sense. Oh well, what can you expect from a $50,000 vehicle anyway. Shame on Lexus for letting this error continue.

lepoch

I guess I could pull the fuse for the GPS unit to force a cold start?

loflin

BobsGX, I think we are discussing two different things.

Lepoch is talking about the Lat/Lon co-ords being off. This is set by the GPS receiver, receiving signals from the Sats.

You are talking about errors in the Map. Errors in the map are due to the map maker and their database.

A GPS error is caused by some real h/w error in the GPS receiver.

Lepoch is looking for someway to do a hard reset on the GPS receiver to see if it will correct itself.

Lepoch, I don't know how to do that. But in reality whenever a GPS turns on, it is a cold start. It searches for Sats and then begins the calculations.

I know you say you know the exact Lat/Lon for your house, but are you 110% sure that is correct?

I would try what Taco said, and sample with some other GPS devices (handheld or cars with Nav). Or if you know where a US Geo Survey marker is near you, you could verify with that.

lepoch

I am 700% certain. I live near an airport and the geocords reported by the GPS are about a degree off in longitude. Additionally I have looked at the survey plats for my house, as well as two commercial mapping programs, google earth, and two handheld GPS units.

SilverLady

Bob - If I remember some of the reading I did on the Nav unit, the maps are street level, not house number level (other than possibly the set addresses for POIs). The read the road, then calculate the approximate location of house numbers.

My house number is particularly weird - I wound up correcting the location by hand and just leaving the incorrect number. I am at the end of a cul de sac, and one house number next door is totally off from mine - a house all the way down the block has the odd number right before my even number. Not only does the GX nav put me there, but so does most of the online mapping software (Mapquest, etc.).

Not a big deal as I know how do get down my block, but our own community ambulance once took at least an extra five minutes to get to our house for an emergency because they kept wandering around the corners at the other end looking for my house.

Tin Star

The distance relative to a degree of latitude is fairly consistent the world over except for polar flattening. Longitude however varys according to latitude. I really doubt that your longitude is off by a degree. I did the calculation for Va and 1 degree error = 55.2407 statute miles.

Tin Star

To continue with my previous post. A GPS unit is just a radio receiver with a mathematical formula plugged in to calculate time/distance. The variables between manufacturers is: at what point do I round off my answer ?

SilverLady

Since you piqued my curiousity, I went out and checked mine.

I checked my lat/long using the terraserver site from Microsoft - typed in my address, clicked on the button to show coordinates, and then picked out the square with the location of my house from the overhead satellite photo. This gave me a "box" around my house to nearest fraction of a second.

I couldn't find a way to show realtime lat/longatude with the GX Nav controls, but I went to the home memory point and clicked info. The degrees and minutes matched exactly, and the seconds were pretty close if I approximated between the points. I realize this isn't as good as a direct real time reading, but the location icon did show me as "home" - it matched up on the map to where I was.

Tin Star is correct about a degree meaning a lot - if it was actually reading one degree off you would have wildly different real time location points.

Kash

if you want to find gps chords there is a way to get it with out going to the menu.. just go to the emergency screen and it'll tell you your cords

SilverLady

Thanks, Kash! I guess that makes some kind of sense, but not exactly intuitive...

I tried it and the coordinates from inside my gargage still seem right on. Perhaps the initial poster will check that screen to see if his still appear incorrect.

BobsGX

Thanks SilverLady,

This explanation does make the most sense since the numbers on my street while they do increase accordingly, I don't know who came up with the house numbers since some go 117,119,121 and then jumps to 135, 141. But what gets me is I has a 2005 Dodge Magnum RT with factory navigation and it had me at my correct house number which is 121. The 05 and now my 06 GX has me at 141. I just don't understand how the 2 numbers can be different since the mapping software is made for Lexus and Chrysler by the same mapping company which is Navteq.

Tin Star

There are at least two possible explanations for this:

1. As I stated earlier some units round off the computations at different points.

2. The placement of the antenna can make a difference from vehicle to vehicle in whether or not it can still see the sats as you approach your house. For instance lets say the Dodge has an antenna that can track the sats all the way from the time you enter your street and right into your garage. Now suppose the GX looses the lock on the sats as you turn onto your street. The vehicle is still moving and the speedo input is still causing it to update your position (just not as accurately).

I don't particularly like the idea of the speedometer input but I guess it might be necessary in some parts of the country. I have been running GPS tracking units in my vehicle for years and have never found the need for anything but a good antenna. I don't however, drive in NY city or in the Rockies.