My First Track Day....Video Link Inside

[Boxster586]

MikenOH,

That is SUPER advice. I will do that for my August 6 track day.

Thank you.

[MikenOH]

The data logger setup was a cheap investment:
1 MOT Q9c that I no longer used as a phone
1 Qstarz 818xt gps receiver--$70
1 Race Chrono software----free


The GPS receiver and phone communicate via a bluetooth connection; supposedly there are OBDII readers out there that will work with the Porsche ECM to pull in engine data to this mix.

To do the data overlay on the video I bought a program on line for $25--race render--which is a simple plug and play setup to match your video with the track data; very simple to synchronize and I highly recommend it.

Putting all that technical stuff aside, it's critical to remember that we're all out there for fun, not making our living at this so we need to be courteous drivers--giving and taking point overs when needed and not letting our egos get in the way of having of having a good time.

[Boxster586]

Originally Posted by MikenOH

The data logger setup was a cheap investment:
1 MOT Q9c that I no longer used as a phone
1 Qstarz 818xt gps receiver--$70
1 Race Chrono software----free


The GPS receiver and phone communicate via a bluetooth connection; supposedly there are OBDII readers out there that will work with the Porsche ECM to pull in engine data to this mix.

To do the data overlay on the video I bought a program on line for $25--race render--which is a simple plug and play setup to match your video with the track data; very simple to synchronize and I highly recommend it.

Putting all that technical stuff aside, it's critical to remember that we're all out there for fun, not making our living at this so we need to be courteous drivers--giving and taking point overs when needed and not letting our egos get in the way of having of having a good time.

Thanks again Mike. I'll likely have more questions for you when I begin this process but why is the Qstarz 818xt gps receiver needed? If my Android phone already has navigation, do I still need the receiver?

[MikenOH]

Originally Posted by Boxster586

Thanks again Mike. I'll likely have more questions for you when I begin this process but why is the Qstarz 818xt gps receiver needed? If my Android phone already has navigation, do I still need the receiver?

To get an accurate position on where you are on the track at a given point in time, you need to get numerous position reports/second because of the speeds involved.

818xt is capable of providing position reports at 10Hz--10 reports/ second. I usually have mine locked at 5hz--5 reports/second because of limitations on my phone. Your generic android phone GPS usually runs at 1Hz--1 position report/second.

At 60mph, you're covering 88 feet/second; with a GPS running 1 position report/second going down the interstate this is no big deal--accurate enough for your purposes. On a race track at twice that speed--say 180'/second--your position reports can be off by nearly 60 yards at those speeds, which will compromise your track data as far as how fast you were going at what point on the track.
If you look at some youtube posters using an iPhone/harry's lap timer--assuming they are just using the phone's internal gps--this lag in speed vs. the video is very apparent; you know the guy is accelerating but the indicated speed seems to move slowly--then boom, it's +20mph faster than it was a second ago.

So, to put it simply, because of the speeds on the track, you need something faster than 1hz reporting if you want accurate speeds at a given location. 10 Hz would be great but a 5hz gps device seems to work fine for me.

Hope this helps; BTW Qstarz also sells a complete data logger--does the function of the RC software--besides records position reports-- for about $170.
Here's a link to Qstarz:
Shop QSTARZ | QSTARZ Q1000eX GPS Lap Timer

[Topless]

Originally Posted by MikenOH

To get an accurate position on where you are on the track at a given point in time, you need to get numerous position reports/second because of the speeds involved.

818xt is capable of providing position reports at 10Hz--10 reports/ second. I usually have mine locked at 5hz--5 reports/second because of limitations on my phone. Your generic android phone GPS usually runs at 1Hz--1 position report/second.

At 60mph, you're covering 88 feet/second; with a GPS running 1 position report/second going down the interstate this is no big deal--accurate enough for your purposes. On a race track at twice that speed--say 180'/second--your position reports can be off by nearly 60 yards at those speeds, which will compromise your track data as far as how fast you were going at what point on the track.
If you look at some youtube posters using an iPhone/harry's lap timer--assuming they are just using the phone's internal gps--this lag in speed vs. the video is very apparent; you know the guy is accelerating but the indicated speed seems to move slowly--then boom, it's +20mph faster than it was a second ago.

So, to put it simply, because of the speeds on the track, you need something faster than 1hz reporting if you want accurate speeds at a given location. 10 Hz would be great but a 5hz gps device seems to work fine for me.

Hope this helps; BTW Qstarz also sells a complete data logger--does the function of the RC software--besides records position reports-- for about $170.
Here's a link to Qstarz:
Shop QSTARZ | QSTARZ Q1000eX GPS Lap Timer

A quick clarification on this...
I am a fan of RaceChrono software and use a 5hz Qstarz GPS receiver with it but... You can still get very high positional accuracy and lap times within 5/100s of a second using a 1hz external receiver and Harry's software (internal phone GPS receivers are very low resolution). We run a pair of matched Spec Boxsters and I use RC while my brother runs Harry's Laptimer. Harry's uses interpolation to give highly accurate sector times and positional data. The timing and data results are very close between the two GPS products. I still prefer RaceChrono for lap analysis but both systems work very well and both are within 5/100ths of our transponder lap times. It's not quite as simple as just comparing GPS sample rate in Hz.

[MikenOH]

Originally Posted by Topless

A quick clarification on this...
I am a fan of RaceChrono software and use a 5hz Qstarz GPS receiver with it but... You can still get very high positional accuracy and lap times within 5/100s of a second using a 1hz external receiver and Harry's software (internal phone GPS receivers are very low resolution). We run a pair of matched Spec Boxsters and I use RC while my brother runs Harry's Laptimer. Harry's uses interpolation to give highly accurate sector times and positional data. The timing and data results are very close between the two GPS products. I still prefer RaceChrono for lap analysis but both systems work very well and both are within 5/100ths of our transponder lap times. It's not quite as simple as just comparing GPS sample rate in Hz.

Topless
Thanks for the clarification; a question or two:

With Harry's, you use an external 1 hz GPS receiver and the software interpolation capability gives it the accuracy of a 5hz receiver? Which receiver was your brother running?

I guess my views on Harry's was colored by the guys I knew that used it running their iPhones for GPS data--good to know!

Just out of curiosity, what kind of analysis for harry's offer relative to RC?
Also, have they fixed that every other lap issue?

[Topless]

Originally Posted by MikenOH

Topless
Thanks for the clarification; a question or two:

With Harry's, you use an external 1 hz GPS receiver and the software interpolation capability gives it the accuracy of a 5hz receiver? Which receiver was your brother running?

I guess my views on Harry's was colored by the guys I knew that used it running their iPhones for GPS data--good to know!

Just out of curiosity, what kind of analysis for harry's offer relative to RC?
Also, have they fixed that every other lap issue?

My brother uses the Tom Tom mount with his iphone/Harry's which supplies a solid mount, power and a hi-res 1hz GPS receiver. Our cars run nearly identical lap times and we often compare between data loggers and our official posted transponder times. Harry's lap time/sector time accuracy is every bit as good as my 5hz w/RaceChrono. Positional accuracy mid corner is still a little better with the 5hz RC. There are now a few 5hz & 10hz receivers available for Harry's but I think they are $170ish.

The lap analysis feature with RC is a very intuitive tool where you can look at two laps running slightly different setups or strategies and compare corner entry/exit speeds with a graph and track overlay. I use this feature a lot and last I looked Harry's was not as good. HLT did just come out with a major software revision so it might be better now. Both apps are excellent learning tools once you get beyond the basics of performance driving and start chasing 1/10ths and TT championships.

More on GPS laptimer accuracy using Harry's. This is pretty consistent with what we see doing data comparisons:
http://gps-laptimer.de/GPS_and_Accuracy.html