GPS Positioning problem
09-25-06, 04:04 PM
#61
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150*F should be well within spec of the receiver and shouldn't cause an issue. However, that being said, there is a GPS xtal (crystal oscillator or Xtal) either internal to the chipset or externally on the module (or both). Xtals are very hard to manfacture and production lots can vary widely. This is mitigated through process control at the xtal manufacturer, the GPS mfg and the OEM (Toyota). It is quite possible this is a oscillator issue. If so, it would easily cause the unit to lose lock at high (or low) temps. It would not explain position jumps.
It's also just as likely that another component on the board is having heat related issues. An LDO could be acting up causing the supply voltage to the GPS receiver to fluctuate and hence, degrade performance.
It's also just as likely that another component on the board is having heat related issues. An LDO could be acting up causing the supply voltage to the GPS receiver to fluctuate and hence, degrade performance.
Last edited by Operation; 09-25-06 at 04:09 PM.
09-25-06, 05:12 PM
#62
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On a different point, is there a variation in signal strength from the satellites at various times during the day? I've noticed that I rarely (if ever) lose lock at night, sometimes lose it in the morning or evening, but frequently lose it midday. I've seen this happen even on cold rainy days when the dashboard was cold to the touch.
09-25-06, 05:53 PM
#63
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Generally speaking, with Dead Reckoning, when there is good GPS signal, the sensor inputs (speed pulse/wheel tick) and gyroscope are not used. In times of bad GPS (low signal levels) the nav systems takes a 'blended' approach using both the GPS and sensor-based inputs. In times of zero GPS coverage (parking garage) then it's all sensors.
A position jump is likely noise related interference somewhere in the Nav unit. The GPS receiver may see 'ghost satellites' and use them in the position solution. This can impare the quality of the position data significantly.
Also, as the GPS birds are always in motion throughout the sky, you will get different signal quality constantly. You will never see the same signal levels throughout the day. Sometimes they are stronger, other times weaker depending on how many Satellites are in view and their location in the sky. As the Birds leave the visible sky, new ones come into view and so forth.
Nighttime shouldn't give any stronger levels than any other time of day. However, weather, atmospheric conditions (mostly in the ionosphere) and solar conditions (flares, etc) can degrade GPS precision.
A position jump is likely noise related interference somewhere in the Nav unit. The GPS receiver may see 'ghost satellites' and use them in the position solution. This can impare the quality of the position data significantly.
Also, as the GPS birds are always in motion throughout the sky, you will get different signal quality constantly. You will never see the same signal levels throughout the day. Sometimes they are stronger, other times weaker depending on how many Satellites are in view and their location in the sky. As the Birds leave the visible sky, new ones come into view and so forth.
Nighttime shouldn't give any stronger levels than any other time of day. However, weather, atmospheric conditions (mostly in the ionosphere) and solar conditions (flares, etc) can degrade GPS precision.
09-25-06, 07:06 PM
#64
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This has happened to me. As I think I previously reported, I was driving down a very straight highway in perfectly clear weather, when the nav suddenly jumped my position into the center of a city! I assume it was the city the highway runs adjacent to, but the street names weren't immediately familiar to me.
09-26-06, 12:05 AM
#65
Hi Guys,
Just posting my .02. As an employee of a GPS chipset manufacturer, I can tell you anything you need to know about GPS.
I'd be willing to wager this is a jamming issue from some electronics close to the GPS antenna/module. A car is a very noisy place especially one jam-packed with electronics like the Lexus. It's also possible the antenna is sub-optimal or the connector is loose or the GPS receiver isn't properly shielded. In-band jamming, would explain a lot of the issues you guys are seeing (long cold-starts, position jumps, etc). Radar detectors, metalic tint and even cell-phone modems can cause interference issues. LCDs are also a notorious source for GPS jamming.
I can say with strong confidence this isn't a heat issue. Unless, I am wrong here, most of the Japanese auto mfg's use a Nippon company called Furuno (you might be familiar with their fish-finder consumer products). In any case, the Furuno receiver is spec'd to the automotive temp. operating range of -40 to +85C. That's right celsius. I doubt any of you operating your vehicles anywhere close to the maximum ratings.
Just posting my .02. As an employee of a GPS chipset manufacturer, I can tell you anything you need to know about GPS.
I'd be willing to wager this is a jamming issue from some electronics close to the GPS antenna/module. A car is a very noisy place especially one jam-packed with electronics like the Lexus. It's also possible the antenna is sub-optimal or the connector is loose or the GPS receiver isn't properly shielded. In-band jamming, would explain a lot of the issues you guys are seeing (long cold-starts, position jumps, etc). Radar detectors, metalic tint and even cell-phone modems can cause interference issues. LCDs are also a notorious source for GPS jamming.
I can say with strong confidence this isn't a heat issue. Unless, I am wrong here, most of the Japanese auto mfg's use a Nippon company called Furuno (you might be familiar with their fish-finder consumer products). In any case, the Furuno receiver is spec'd to the automotive temp. operating range of -40 to +85C. That's right celsius. I doubt any of you operating your vehicles anywhere close to the maximum ratings.
Perhaps it's my radar detector that's playing a role in my misguidance, but why then wouldn't the radar detector ALWAYS pose problems? Or more consistantly pose problems? The tracking errors only seem to happen once every couple weeks or so...
09-26-06, 08:47 AM
#66
Super Moderator
In my case, the only external electronic device in the car is my iPod, located far away in the armrest. And on the day (about two weeks ago) that the nav system thought I was driving in the ocean, the iPod was at home. Oh, and my cell phone too. (Keeping my fingers crossed, but the system hasn't glitched in over two weeks)
09-26-06, 09:21 AM
#67
I don't think he necessarily means external electronics. My read is that he was talking about the other built-in gadgets like the bluetooth hands-free phone interface, which would be located in physical proximity to the GPS unit and antenna.
In my case, the only external electronic device in the car is my iPod, located far away in the armrest. And on the day (about two weeks ago) that the nav system thought I was driving in the ocean, the iPod was at home. Oh, and my cell phone too. (Keeping my fingers crossed, but the system hasn't glitched in over two weeks)
In my case, the only external electronic device in the car is my iPod, located far away in the armrest. And on the day (about two weeks ago) that the nav system thought I was driving in the ocean, the iPod was at home. Oh, and my cell phone too. (Keeping my fingers crossed, but the system hasn't glitched in over two weeks)
Good luck with yours, let's hope you never have to reset!
09-26-06, 10:46 AM
#68
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I frequently run with a V1 and I've never had a position jump with or without the detector, and I put it low on the windshield, not high, to better detect laser events. The Valentine is better shielded than most though.
09-26-06, 01:27 PM
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quick update...
dealer gave me a headfake last weds claiming it was fixed but when i arrived and took the mechanic for a drive. the nav failed again but with a witness this time. anyways the guys took it back for more work and today i received some good news when i called them. supposedly there is some sort of plastic cable the connects to the nav from the receiver that was broken. so im assuming that the connection from the satellite was not being relayed at all or intermittently. anyway, they replaced this "connection". seems to be a manufacturing defect from the mothership.
dealer gave me a headfake last weds claiming it was fixed but when i arrived and took the mechanic for a drive. the nav failed again but with a witness this time. anyways the guys took it back for more work and today i received some good news when i called them. supposedly there is some sort of plastic cable the connects to the nav from the receiver that was broken. so im assuming that the connection from the satellite was not being relayed at all or intermittently. anyway, they replaced this "connection". seems to be a manufacturing defect from the mothership.
09-26-06, 03:22 PM
#70
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When you get it back, can you post the information from your repair order, including the part numbers and descriptions of the part(s) they replaced? Especially if the repair actually worked. 
09-28-06, 06:19 AM
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GOT My IS BACK!!!
and as of now it is working fine...well at least for the past 3 days. I just hope to never go back in for this problem again considering into 2 months of attempted repair. IF those guys at the dealership just listened to me the 2nd time i took the car in the problem would have been resolved faster.
Ok for those of you experiencing the problem still i will try to attempt to explain how they fixed it. I am not a technical person but i hope the manner in which i describe the process is helpful.
here goes... so satellites sends signal to our cars and our antennas receive them. once the data is received, it is then transfered to the nav computer which is located beneath the LCD screen and inaccessable unless you remove the cover. the problem they found is that the data jack connecting the antenna to the back of the nav unit was not plugged in properly. i guess another way to describe it is when you connect an ethernet cable to your laptop. but in this case there is a spring loaded jack that spreads open upon insertion into the slot. it appears that when the car was manufactured, when the jack was inserted (by robots?) , it was jammed into place with the springs failing to open thus causing a faulty connection.
this is why the "rebooting" or erase and reinstall are pointless because the signal transfer to the nav computer was intermittent.
hope this helps.
-mike
and as of now it is working fine...well at least for the past 3 days. I just hope to never go back in for this problem again considering into 2 months of attempted repair. IF those guys at the dealership just listened to me the 2nd time i took the car in the problem would have been resolved faster.
Ok for those of you experiencing the problem still i will try to attempt to explain how they fixed it. I am not a technical person but i hope the manner in which i describe the process is helpful.
here goes... so satellites sends signal to our cars and our antennas receive them. once the data is received, it is then transfered to the nav computer which is located beneath the LCD screen and inaccessable unless you remove the cover. the problem they found is that the data jack connecting the antenna to the back of the nav unit was not plugged in properly. i guess another way to describe it is when you connect an ethernet cable to your laptop. but in this case there is a spring loaded jack that spreads open upon insertion into the slot. it appears that when the car was manufactured, when the jack was inserted (by robots?) , it was jammed into place with the springs failing to open thus causing a faulty connection.
this is why the "rebooting" or erase and reinstall are pointless because the signal transfer to the nav computer was intermittent.
hope this helps.
-mike
09-28-06, 10:21 AM
#72
GOT My IS BACK!!!
and as of now it is working fine...well at least for the past 3 days. I just hope to never go back in for this problem again considering into 2 months of attempted repair. IF those guys at the dealership just listened to me the 2nd time i took the car in the problem would have been resolved faster.
Ok for those of you experiencing the problem still i will try to attempt to explain how they fixed it. I am not a technical person but i hope the manner in which i describe the process is helpful.
here goes... so satellites sends signal to our cars and our antennas receive them. once the data is received, it is then transfered to the nav computer which is located beneath the LCD screen and inaccessable unless you remove the cover. the problem they found is that the data jack connecting the antenna to the back of the nav unit was not plugged in properly. i guess another way to describe it is when you connect an ethernet cable to your laptop. but in this case there is a spring loaded jack that spreads open upon insertion into the slot. it appears that when the car was manufactured, when the jack was inserted (by robots?) , it was jammed into place with the springs failing to open thus causing a faulty connection.
this is why the "rebooting" or erase and reinstall are pointless because the signal transfer to the nav computer was intermittent.
hope this helps.
-mike
and as of now it is working fine...well at least for the past 3 days. I just hope to never go back in for this problem again considering into 2 months of attempted repair. IF those guys at the dealership just listened to me the 2nd time i took the car in the problem would have been resolved faster.
Ok for those of you experiencing the problem still i will try to attempt to explain how they fixed it. I am not a technical person but i hope the manner in which i describe the process is helpful.
here goes... so satellites sends signal to our cars and our antennas receive them. once the data is received, it is then transfered to the nav computer which is located beneath the LCD screen and inaccessable unless you remove the cover. the problem they found is that the data jack connecting the antenna to the back of the nav unit was not plugged in properly. i guess another way to describe it is when you connect an ethernet cable to your laptop. but in this case there is a spring loaded jack that spreads open upon insertion into the slot. it appears that when the car was manufactured, when the jack was inserted (by robots?) , it was jammed into place with the springs failing to open thus causing a faulty connection.
this is why the "rebooting" or erase and reinstall are pointless because the signal transfer to the nav computer was intermittent.
hope this helps.
-mike
09-28-06, 11:11 AM
#73
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This is interesting information considering Lexus just told me that they are working on a software fix for the navigation system on all the IS's!
Unfortunately, it won't be available for a month!!
Lex
Unfortunately, it won't be available for a month!!
Lex
09-28-06, 01:09 PM
#74
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For those of you that need a quick recap of the problems I had with my Nav/GPS unit please read before taking your car into the shop...
on a drive in the last week of july, my nav displayed my car traveling on the highway properly but 30 minutes into my drive i noticed the positioning on the screen was not on the road. in the past i had momentary glitches where it lagged for a few second but quickly corrected the positioning. on this occasion the "computer" made no attempt to correct my positioning. the car would "travel" on the screen but would not follow the roads...instead it would be cutting through the blocks...(i live in/around NYC)
I recalibrated the car myself but 20 minutes into the drive the same problem occurred. i also discovered that every time i turn on the car the gps readout had me positioned 10-30 miles from my current position and in many instances in the middle of the atlantic ocean.
The problem persisted despite recalibration performed by myself. Took the car in for the problem...dealer re-installed software. i took back car but issues remained. brought it in for 2nd time...delete re-install was attempted again despite my suggestion for checking connection. went to pick up car when called claiming it was fixed. car failed again going home. took it to dealer for 3rd time and told them to keep it for as long as they can...received call a week later claiming the car was fixed. took mechanic for ride and instantly failed. back to the garage... and finally to look at the connection. problem solved...for now.
If you turn on your car and the positioning shows that you are miles away or nav is not following roads for extended periods. you may need to replace the jack.
on a drive in the last week of july, my nav displayed my car traveling on the highway properly but 30 minutes into my drive i noticed the positioning on the screen was not on the road. in the past i had momentary glitches where it lagged for a few second but quickly corrected the positioning. on this occasion the "computer" made no attempt to correct my positioning. the car would "travel" on the screen but would not follow the roads...instead it would be cutting through the blocks...(i live in/around NYC)
I recalibrated the car myself but 20 minutes into the drive the same problem occurred. i also discovered that every time i turn on the car the gps readout had me positioned 10-30 miles from my current position and in many instances in the middle of the atlantic ocean.
The problem persisted despite recalibration performed by myself. Took the car in for the problem...dealer re-installed software. i took back car but issues remained. brought it in for 2nd time...delete re-install was attempted again despite my suggestion for checking connection. went to pick up car when called claiming it was fixed. car failed again going home. took it to dealer for 3rd time and told them to keep it for as long as they can...received call a week later claiming the car was fixed. took mechanic for ride and instantly failed. back to the garage... and finally to look at the connection. problem solved...for now.
If you turn on your car and the positioning shows that you are miles away or nav is not following roads for extended periods. you may need to replace the jack.
10-25-06, 09:35 PM
#75
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Positioning off when I hit a manhole
Hi,
I've recently started having positioning problems with the NAV and the other day as I was driving away from my home, I drove over a manhole and the NAV positioning jumped to another street. It took about 5 mins to find it way back to a major road.
Another time this happened was when I got pulled over by CHP and I had to pull over to the side of the road (somewhere near Merced, CA off of Hwy 99). When I got back on the road, the positioning was way off. It positioned itself some 100 miles away. This time, I manually calibrated the positioning and it still couldn't find its way. It took about 30 mins to get to an area where it automatically positioned itself on the right road.
Should droving over a small manhole or pulling to the side of the road mess up the NAV positioning?
Do you think I should take it in or just monitor it until it gets worst? Thanks!!
I've recently started having positioning problems with the NAV and the other day as I was driving away from my home, I drove over a manhole and the NAV positioning jumped to another street. It took about 5 mins to find it way back to a major road.
Another time this happened was when I got pulled over by CHP and I had to pull over to the side of the road (somewhere near Merced, CA off of Hwy 99). When I got back on the road, the positioning was way off. It positioned itself some 100 miles away. This time, I manually calibrated the positioning and it still couldn't find its way. It took about 30 mins to get to an area where it automatically positioned itself on the right road.
Should droving over a small manhole or pulling to the side of the road mess up the NAV positioning?
Do you think I should take it in or just monitor it until it gets worst? Thanks!!