Car in Wrong Location on my PCM Nav
08-27-2016, 01:09 AM
#16
Three Wheelin'
Calibration is only used for an electronic compass, typically in a figure 8 or at least a 360. There is no calibration for GPS.
OP. The only reason a GPS produces poor readings is when it isn't receiving signals from enough satellites, typically due to interference from tall structures, too many trees, shielding from a human body (aka a bag of water), being indoors, or... a poorly performing antenna. I am certain this is the problem in your case unless you live in the midst of skyscrapers.
NYC is still at a low enough latitude that it should be able to pick up enough satellites for an error radius of about 3 meters... again, unless you are amongst skyscrapers. It is true that the GPS satellites are all equatorial, but at geosynchronous orbit at more than 22000 miles they are easily in the line of sight of New York. The high latitude problem is just an excuse if they try to use that one. The only reasonable argument is if you live in the land of skyscrapers. Downtown LA is a known problem spot for example.
(I've worked on tracking apps for the military and transit systems and am familiar with a lot of the gotchas here.)
OP. The only reason a GPS produces poor readings is when it isn't receiving signals from enough satellites, typically due to interference from tall structures, too many trees, shielding from a human body (aka a bag of water), being indoors, or... a poorly performing antenna. I am certain this is the problem in your case unless you live in the midst of skyscrapers.
NYC is still at a low enough latitude that it should be able to pick up enough satellites for an error radius of about 3 meters... again, unless you are amongst skyscrapers. It is true that the GPS satellites are all equatorial, but at geosynchronous orbit at more than 22000 miles they are easily in the line of sight of New York. The high latitude problem is just an excuse if they try to use that one. The only reasonable argument is if you live in the land of skyscrapers. Downtown LA is a known problem spot for example.
(I've worked on tracking apps for the military and transit systems and am familiar with a lot of the gotchas here.)
WHAT?
Hope I never need to use one of the transit systems you worked on!
Please see attached map of the positions for 25/08/16. If they all were on an equatorial orbit, you'd never be able to get a 3-way fix. And that's a good thing since I'm currently 300km. off the coast of the Philippines.
08-27-2016, 09:04 AM
#17
Rennlist Member
It is true that the GPS satellites are all equatorial
WHAT?
Hope I never need to use one of the transit systems you worked on!
Please see attached map of the positions for 25/08/16. If they all were on an equatorial orbit, you'd never be able to get a 3-way fix. And that's a good thing since I'm currently 300km. off the coast of the Philippines.
WHAT?
Hope I never need to use one of the transit systems you worked on!
Please see attached map of the positions for 25/08/16. If they all were on an equatorial orbit, you'd never be able to get a 3-way fix. And that's a good thing since I'm currently 300km. off the coast of the Philippines.
And by the way, your mention of a "3-way fix" is incorrect too. You are thinking of triangulation, but GPS uses a form of trilateration. With three satellites your location is still considered to be of poor quality; not good enough for figuring out what street you are on. A minimum of four is needed for good enough accuracy to begin to locate your position on a road, five or six are preferred and is the reason the constellation is designed so that six are visible at any one time. But yes, I certainly blew it when I got too nerdy in my attempted post earlier.
For OP, all that matters is that his GPS is not picking up enough good signals. Have they tried replacing the GPS antenna? Any argument that the error is just the way it is falls short if you can get in any other Porsche on their lot and get more accurate positioning.
08-27-2016, 10:04 AM
#18
Pro
Thread Starter
Wow. Thanks for the in depth information and help. I really appreciate it.
The dealer states:
It has to do with satellite signals or PCM settings and they need to see the car.
As you stated above it is likely a faulty antenna.
Out of curiosity I just wonder if the antenna is defective out of nowhere or it became defective or momentarily unplugged after installing a simple wire from the fuse box to my radar which hangs above the mirror.
They did run the wire along the A pillar which is noted in the diagram above. Could a wire or antenna booster have come loose???
Either way your info makes me confident that they will investigate and get it fixed.
Once again thanks everyone for the input from everyone.
Great Forum. Great Support.
I'll keep you posted. Hopefully I can get the car to the dealer within 2 weeks.
The dealer states:
It has to do with satellite signals or PCM settings and they need to see the car.
As you stated above it is likely a faulty antenna.
Out of curiosity I just wonder if the antenna is defective out of nowhere or it became defective or momentarily unplugged after installing a simple wire from the fuse box to my radar which hangs above the mirror.
They did run the wire along the A pillar which is noted in the diagram above. Could a wire or antenna booster have come loose???
Either way your info makes me confident that they will investigate and get it fixed.
Once again thanks everyone for the input from everyone.
Great Forum. Great Support.
I'll keep you posted. Hopefully I can get the car to the dealer within 2 weeks.
08-27-2016, 07:14 PM
#19
Three Wheelin'
Well duh. Thank you for the correction. Embarrassingly enough I got my thoughts on GPS satellites and DirectTV satellites confused. I must be getting old (I just checked that, yep). Fortunately for our apps, I don't really have to know where the heck the satellites are, just what the GPS interface reports. I've changed that post so as not to confuse those unfortunate enough to read my misleading thoughts!
And by the way, your mention of a "3-way fix" is incorrect too. You are thinking of triangulation, but GPS uses a form of trilateration. With three satellites your location is still considered to be of poor quality; not good enough for figuring out what street you are on. A minimum of four is needed for good enough accuracy to begin to locate your position on a road, five or six are preferred and is the reason the constellation is designed so that six are visible at any one time. But yes, I certainly blew it when I got too nerdy in my attempted post earlier.
For OP, all that matters is that his GPS is not picking up enough good signals. Have they tried replacing the GPS antenna? Any argument that the error is just the way it is falls short if you can get in any other Porsche on their lot and get more accurate positioning.
And by the way, your mention of a "3-way fix" is incorrect too. You are thinking of triangulation, but GPS uses a form of trilateration. With three satellites your location is still considered to be of poor quality; not good enough for figuring out what street you are on. A minimum of four is needed for good enough accuracy to begin to locate your position on a road, five or six are preferred and is the reason the constellation is designed so that six are visible at any one time. But yes, I certainly blew it when I got too nerdy in my attempted post earlier.
For OP, all that matters is that his GPS is not picking up enough good signals. Have they tried replacing the GPS antenna? Any argument that the error is just the way it is falls short if you can get in any other Porsche on their lot and get more accurate positioning.
08-28-2016, 03:32 PM
#20
Rennlist Member
FiveRiversGTS: I was just out and thought to check something. On the PCM buttons, press Info then press Location Info on the display that comes up on the screen. This will lead to another screen that gives a more raw GPS report. While it does not directly tell you what the currently calculated error radius is, it does tell you how many satellites it is currently receiving at the far right of the screen. If this number is less than 6 then that is a problem for getting enough accuracy to properly place you on a street... or as stated earlier, below the minimum of 4 then no reasonable reading can be observed.
I checked my readout at various times in the drive. Out in the open it showed as many as 10 satellites. In my heavily treed neighborhood it dropped to 7. It would be interesting to see how many your PCM is reporting.
I checked my readout at various times in the drive. Out in the open it showed as many as 10 satellites. In my heavily treed neighborhood it dropped to 7. It would be interesting to see how many your PCM is reporting.
08-28-2016, 05:38 PM
#22
Pro
Thread Starter
Originally Posted by R_Rated
typically a GPS tracking device is hidden and the primary driver has no idea it's there. Have any reason someone would hire a PI?
The following users liked this post:
RichardA (06-12-2021)
08-28-2016, 11:02 PM
#25
Rennlist Member
I just went out and took some shots of mine. While sitting in the garage, the PCM still picked up 4 satellites within 30-45 seconds. Backing out of the garage but still under tree cover, it went up to 6 and an altitude reading appeared. Moving out into the street it went up to 8.
You can see by the clock timestamps at the bottom these shots were within 2 minutes of each other. Interestingly, you can see that even at 6 satellites it couldn't identify the street I was on (maybe because I was in the long driveway though?). Although I missed a photo of 7 before it turned to 8, at 7 the street was correctly identified. I've blurred out the street name and some lat/lon digits for privacy reasons. Here the PCM screen shots.
09-09-2016, 11:13 PM
#26
Pro
Thread Starter
Finally got it fixed. Took it into the dealer on Tuesday afternoon with a last minute same day appointment. (Not the same dealer that installed radar wire, took it to the dealer where it was purchased)
The dealer did the basic initial testing on the antenna, wires, connections, etc. Everything was okay in regards to the external connections and parts. Within a few hours they decided they would have to contact Porsche for the next step.
Gave me a loaner 2017 Macan Base with 425 miles. Nice ride!
The next day I was notified that the next step was to replace the PCM unit. The Porsche Field Tech Manager(FTM) was onsite on that Wednesday working with the tech to determine this.
The part came in within two days and the car was ready today Friday morning.
Got the car back and it works just fine. I see up-to 10 satellites while driving. It's version 4.76 and the previous was 4.75
It was mysterious how just the navigation portion only was affected. They explained it was like a computer and things can happen.
Thank you everyone for your help.
Much appreciated.
Just wanted to get back to you with my results.
The dealer did the basic initial testing on the antenna, wires, connections, etc. Everything was okay in regards to the external connections and parts. Within a few hours they decided they would have to contact Porsche for the next step.
Gave me a loaner 2017 Macan Base with 425 miles. Nice ride!
The next day I was notified that the next step was to replace the PCM unit. The Porsche Field Tech Manager(FTM) was onsite on that Wednesday working with the tech to determine this.
The part came in within two days and the car was ready today Friday morning.
Got the car back and it works just fine. I see up-to 10 satellites while driving. It's version 4.76 and the previous was 4.75
It was mysterious how just the navigation portion only was affected. They explained it was like a computer and things can happen.
Thank you everyone for your help.
Much appreciated.
Just wanted to get back to you with my results.
09-11-2016, 01:22 PM
#27
Rennlist Member
Great news! Thanks for letting us know how it all turned out.
10-27-2016, 02:55 AM
#28
2nd Gear
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I have the same problem. I took it to my shop and they plugged into cars system and it showed there was a antenna problem.
I had the windshield replaced and that was the beginning of my GPS problems, radio works fine.
I'm having the windshield installer return to check to see if the antenna was not reconnected.
I'm still trying to confirm the location of the GPS antenna.
If anyone can confirm it's location (997 GT3) please let me know.
I had the windshield replaced and that was the beginning of my GPS problems, radio works fine.
I'm having the windshield installer return to check to see if the antenna was not reconnected.
I'm still trying to confirm the location of the GPS antenna.
If anyone can confirm it's location (997 GT3) please let me know.
10-27-2016, 10:46 AM
#29
Pro
Thread Starter
Hello, sorry to hear about this problem.
When I first researched this with the help of the posts above, I believe that the GPS antenna is under the plastic cowling on the passenger side just above the cabin air filter when you open the frunk.
See this old post:
https://rennlist.com/forums/997-foru...atellites.html
Also from StormRune's diagrams, I believe there are antenna boosters in the pillar.
Good Luck and let us know what turns up.
When I first researched this with the help of the posts above, I believe that the GPS antenna is under the plastic cowling on the passenger side just above the cabin air filter when you open the frunk.
See this old post:
https://rennlist.com/forums/997-foru...atellites.html
Also from StormRune's diagrams, I believe there are antenna boosters in the pillar.
Good Luck and let us know what turns up.
