During Sprint Cup qualifying at Bristol, I noticed all the cars had GPS transponders on the windshield. Is NASCAR ready to switch off of scoring loops or is this another experiment?

mustang6172 - 22 August 2008 04:05 PM

During Sprint Cup qualifying at Bristol, I noticed all the cars had GPS transponders on the windshield. Is NASCAR ready to switch off of scoring loops or is this another experiment?

The transponders work with the scoring loops to determine position. They've been in use for quite a while.

No, that transponder is located on the fuel tank. NASCAR has been testing a GPS system to replace that one. It mounts to the windshield and is marked with a green dot.

http://www.motorsport.com/photos/nascar-cup/2008/br2/nascarcup-2008-br2-as-0044

mustang6172 - 22 August 2008 10:05 PM

No, that transponder is located on the fuel tank. NASCAR has been testing a GPS system to replace that one. It mounts to the windshield and is marked with a green dot.

http://www.motorsport.com/photos/nascar-cup/2008/br2/nascarcup-2008-br2-as-0044

Thanks, I didn't know that. I wonder if they've had problems with the loop system at some venues?

The advantage of GPS is that it would provide continuous real time positioning in the event of a caution, instead of positioning the field based on the last loop crossed. The downside is that it may not work at every track because of track or grandstand layout blocking satellite acquisition. Bristol would present a challange, I would think, with it's high grandstands.

I thought only the military system would be accurate enough, and fast enough, to mark positions at the speed they're traveling. Unless something has cahnged, the accuracy was only as good as within 3 feet.

Bill

What you see in the right side car window is a TIWI. It is a GPS receiver and transmitter that NASCAR is currently testing as a replacement for the manual scores who currently still score each car. NASCAR primarily uses transponders and loops to score the position of each car on the track. As Mustang6172 mentioned that transponder is actually mounted on the right side of the fuel cell containment well. If you go to page 3 of this forum you will find a post entitled NASCAR scoring system, in that post I posted a couple of pictures one is of a transponder mounted on a car. The post also explains how the system works. As a back up to the loop and transponder system each team supplies a person who sits in race control and they press a button each time their car crosses the start finish line. That button push is capture on the back up computer system so if all else fails they will at least know how many laps each car has completed. The TIWI system is a replacement for the manual scorers each car currently has to have. Basically it does the same thing as the loop system but it is a GPS version. Hobbymanbill expressed some concern that GPS may not be accurate enough, have no fear. Military encryption of GPS satellites has been removed for more that 8 years now, so everyone has the same accuracy, and that is one reason commercial airliners can now fly GPS approaches down to the inch with no outside ground based navigation assistance. WAAS or wide area augmentation system has made GPS very accurate. GPS is sometimes subject to some atmospheric interference and at times GPS satellites are taken out of service for maintenance and updates.

Currently you are more likely to see the system in use in a Truck or Nationwide race than you are on a Cup car. They are however using the system for practice in Cup and I think they have used in four races to date.

If TIWI sounds familiar to you it’s because it is also available for you to mount in your teen’s car so you can keep an eye on their driving habits. Go to TIWI.com. I hope this helped to answer the question.

hobbymanbill - 23 August 2008 09:03 AM

I thought only the military system would be accurate enough, and fast enough, to mark positions at the speed they're traveling. Unless something has cahnged, the accuracy was only as good as within 3 feet.

Bill

If you're referring to the intentional inaccuracy that was originally built into consumer GPS, that was turned off during the Clinton administration. High quality consumer GPS systems nowadays are just as accurate as what the Army uses.

We use GPS data acquisition on a team I work for and its accurate to about 6 inches and .01 seconds when combined with accelerometer data. Certainly there is a system than can provide the resolution (.001 or.0001) that NASCAR needs, but backup systems would still need to be in place.

kaveman12 - 24 August 2008 07:40 PM

We use GPS data acquisition on a team I work for and its accurate to about 6 inches and .01 seconds when combined with accelerometer data. Certainly there is a system than can provide the resolution (.001 or.0001) that NASCAR needs, but backup systems would still need to be in place.

Currently with all the "regular" data systems, the GPS accuracy of 6" (quoted by a few data companies and incorrectly so)is only possible with a GPS trianglation beacon located within the race track.
These gps systems function at 20hz and are highly expensive ($15k-20k) but are capable of within 6 inches of location.
The other ones, operating at 10hz or even 5hz, when mounted on a race car, are lucky to be within the military imposed spec of 3 feet over 1 lap. Add 10 laps to that and the error adds up further and muliplys. A driver cannot rely on being 3-6ft off of the apex when 6 inches is way, way off.
A lot of data companies continue to "claim" the accuracy level as good enough to pinpoint a drivers racing line, but fail to do so.
The only part of the lesser HZ GPS is the ability to judge speed and laptime (replacing a beacon)

A newer GPS technology, L2 is coming but all the satillites needed aren't up yet, but even this technology is triangulated. Though the accuracy is down to within inches, again with 20hz, the costs of the technology is yet to be determined.

Data companies that claim judgement of racing line with GPS anywhere below 3 ft and the system is 10hz or below and without a trianglation beacon, are lying to you.
Even the one using an accelerometer for "adjustment" of the location of the GPS, I know who you are talking about and have used the system, it doesn't do what they say it does. In five laps at Road Atlanta, the car I worked with was 22ft off line, yet he was the third fastest car in the session.
And the GPS systems horsepower and torque ratings weren't even close either.

@SPEEDSENSE:
I know what you're saying. Fortunately, in our case we're more interested in the analog inputs we have in place than the GPS data. All we use the GPS for is time and speed estimates, both of which we can get from other sources.