My map function in my 14C4S starts out to be right on for position when I first get going and then within a few minuts it starts drifiting showing my position to be off by as much as 0.05 miles from actual. Shutting the car off until PCM resets fixes it momentarily and then randomly it starts drifiting again.
Has anyone experienced similar issues? Is there a way to do a hard reset? Is my antenna mulfunctioning?

 

I'd take it. Something is definitely off there.

 

Have you been carrying anything different in the car lately? Either an item you keep in your pocket like a cell phone, or anything else? Sounds like something may be interfering with it, but most likely your software needs a reset.

 

i have recently noticed the same issue which has only happened a few times but usually happens when i come out of an underground parking lot. position corrects itself if i start a route calc. car is in with the dealer today so will let you what they say though i suspect they will just do a reset .

 

GPS doesn't "drift" like other internal position generating devices like INS or Doppler. GPS takes external signals (Satellite transmissions) and applies a formula to arrive at your position. It needs at least four satellites to generate position and altitude. More satellites are better as it can choose more diversely separated satellites to arrive at a better solution. If you are noticing inaccurate positions some of the biggies causing the issue are:

1. Lack of a high number of satellites it is tracking due to obstructions like mountains or buildings. Narrow valleys can cause this as can high-rises in town.

2. hardware issue like a problem with the antenna

3. software issue

The second two should be easily corrected by the dealer.

My only complaint is that our GPS doesn't tell you when it has lost lock with enough satellites to determine position. I notice this going through long tunnels in Europe. It takes its best guess based on your velocity and continues to present position/altitude information without letting you know its degraded. Any cheap Garmin and even Waze will tell you when they have lost lock and to disregard the information. Aircraft I've flown will tell you number of satellites it's tracking and give estimated position errors due to satellite geometry. I think I have seen on a page on the PCM the number of satellites it's tracking but nothing about position error or reliability. For having to acknowledge that Porsche isn't responsible for anything when you use the GPS on startup with the "Confirm" button, I can't see why their lawyers don't make them flash a warning message when the GPS is unreliable.

 

I had the exact same issues on my DD (not a P-car) and the dealership reloaded and updated the Navi software and that solved the problem.