I've had the same thing happen. I've even had it think that I was on a road adjacent to the one I was actually driving on. After driving a short distance, it figures out that it got it wrong, and the pointer snaps to the right place. It's not a nav hack thing, as I haven't performed the nav hack on my car.

Does anyone know whether the government is still intentionally degrading civilian GPS signals (i.e, making them intentionally inaccurate by a few hundred feet so that they are less likely to be used for bomb targetting)?

 

I'm often suffering the same problem even here, in Italy (and still not done the nav hack).
It's strange that a car with such a new and powerful NAV unit doesn't catch the right position so many times.
I'd be curious to know if it uses the new SIRF III GPS chipset to get the position: on my new Asus pda the SIRF III chipset is VERY sensitive and even gets the right position inside the house, 1.5m distant from the window (!), while my old one had to stay absolutely outside to catch the minimal 3 satellites and figure out the position.

More: does anybody know if it's possible to re-calibrate the nav so that Lexy doesn't think to be always about 20 meters behind the correct position? I've lost the turn more than a couple of times because the NAV unit is always a bit late! I tried (but only one time) the re-calibrate option on the nav menu, but it didn't work. Many tks

 

The reason why your NAV sometimes sometimes does not place your position directly on
a roadway is because you need to calibrate it's position. This procedure is explained in
the manual. The software running in the unit will only place your displayed
current position directly onto a road if it's actual GPS calculations are
within a certain distance of the raster map's location of the roadway. There is a
correction factor that you can apply by following the manual.

The NAV unit will NOT be jumpy if you do the hack properly. Yes, the
speed signal still goes to the NAV unit after the hack. It just bypasses
the Multi display unit and fools that part of the system only.

I have hacked my NAV since the second day I had the car without any
problems. Even when I am in a 5 story parking garage on the first floor,
my NAV unit is smooth and follows my movements precicely on
every floor, and you know it is not receiving a GPS signal through all
that concrete and steel.

 

I am interested in doing this hack, but I am not sure if it's going to work the same way as it does without the hack.

 

I mentioned this a few days ago. Clinton officially turned this OFF. When it was ON, I was using Nav in another car and it wasn't really affected because the Nav would snap into position and make up for the deficiency. But my handheld Garmin GPS would definitely be off.

I am seeing some "snapping" going on here in Kansas where the roads are all straight and not even close together. I didn't see this late last year. Reminds me of when SA (selective availability) was turned ON. With the situation in DPRK and all, you never know. I will check it out see if there's any talk.....

 

THE WHITE HOUSE
Office of the Press Secretary
For Immediate Release May 1, 2000
STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY

Today, I am pleased to announce that the United States will stop the intentional degradation of the Global Positioning System (GPS) signals available to the public beginning at midnight tonight. We call this degradation feature Selective Availability (SA). This will mean that civilian users of GPS will be able to pinpoint locations up to ten times more accurately than they do now. GPS is a dual-use, satellite-based system that provides accurate location and timing data to users worldwide. My March 1996 Presidential Decision Directive included in the goals for GPS to: "encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide; and to encourage private sector investment in and use of U.S. GPS technologies and services." To meet these goals, I committed the U.S. to discontinuing the use of SA by 2006 with an annual assessment of its continued use beginning this year.

The decision to discontinue SA is the latest measure in an on-going effort to make GPS more responsive to civil and commercial users worldwide. Last year, Vice President Gore announced our plans to modernize GPS by adding two new civilian signals to enhance the civil and commercial service. This initiative is on-track and the budget further advances modernization by incorporating some of the new features on up to 18 additional satellites that are already awaiting launch or are in production. We will continue to provide all of these capabilities to worldwide users free of charge.

My decision to discontinue SA was based upon a recommendation by the Secretary of Defense in coordination with the Departments of State, Transportation, Commerce, the Director of Central Intelligence, and other Executive Branch Departments and Agencies. They realized that worldwide transportation safety, scientific, and commercial interests could best be served by discontinuation of SA. Along with our commitment to enhance GPS for peaceful applications, my administration is committed to preserving fully the military utility of GPS. The decision to discontinue SA is coupled with our continuing efforts to upgrade the military utility of our systems that use GPS, and is supported by threat assessments which conclude that setting SA to zero at this time would have minimal impact on national security. Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened. This regional approach to denying navigation services is consistent with the 1996 plan to discontinue the degradation of civil and commercial GPS service globally through the SA technique.

Originally developed by the Department of Defense as a military system, GPS has become a global utility. It benefits users around the world in many different applications, including air, road, marine, and rail navigation, telecommunications, emergency response, oil exploration, mining, and many more. Civilian users will realize a dramatic improvement in GPS accuracy with the discontinuation of SA. For example, emergency teams responding to a cry for help can now determine what side of the highway they must respond to, thereby saving precious minutes. This increase in accuracy will allow new GPS applications to emerge and continue to enhance the lives of people around the world.

source: http://www.ngs.noaa.gov/FGCS/info/sa...statement.html

 

Ah...this is what I was trying to describe in my last post and it looks as if others (who haven't performed the hack) are experiencing it, too. I figured it was something that was inherent to the GPS system, overall...

 

I'm convinced the dead reconing still works after the hack.

In this case, I'm quite happy to be proved wrong.

Cheers

 

Thanks, please do. I've also noticed that mine seems less accurate than it was when I first got the car last year. I'm curious to know whether Bush has turned SA back on.

 

Thanks Tuxlex! I'll check better the manual tomorrow and try to recalibrate...

 

I can't find anything at the moment so who knows. It wouldn't surprise me if they turn it off and on from time to time.....

 

Some variances are caused simply by incorrect lat/long data on the DVD itself, particularly in extremely condensed cities where there has been a lot of road construction/rerouting in the last couple of years. Before I bought my IS I had a TomTom 300 in my Audi and it started going a bit off track in downtown Boston (especially around the Dig), in precisely the same areas my IS's nav gets off track.

 

We've noticed similar things happen but not very often. We were on a trip down to NC and notice while we were going down one of the interstates, the gps showed we were about 10 miles into the woods but still running parallel with the interstate. It corrected itself after about 15 mins and was otherwise dead on for the trip. I've had it happen a few other times but like I said...it's normally right on.