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RaceChrono accuracy over Google Earth maps

r1hellmanr1hellman
edited August 2008 in Older versions of RaceChrono
Hi all, I've tried the race chrono a few times now at motorcycle ride days in Australia at Oran Park and Oran South Circuit and I am loving it! Excellent work and thankyou :-) I have compared the times only with a stopwatch and they appear to be very accurate as expected. I am using a Nokia 6110 navigator with the QSTARZ extreme receiver.

I downoaded the laps onto google earth and it isn't very accurate with my position on the track. Several laps it shows me in the dirt or really wide on corners which didn't happen. The satellite signals looked good when I checked it on the day and the excel data I exported shows I was locked to between 6 and 8 satellites. I have the phone set to use the QSTARZ and not the internal receiver. I mount the receiver on the top of the triple clamp with some electrical tape which doesn't move all day. The batteries were charged fully before each day. I have also set the QSTARZ to 5Hz. Have I missed something? I would like to be able to analyse my lines on the best laps to help me to improve, but at the moment the data isn't accurate enough for that. Any ideas? Thankyou. Geoffro

Comments

  • aol_of_RaceChronoaol_of_RaceChrono
    edited August 2008
    The tail section of your bike is better place for the GPS receiver than the triple clamp, but it's probably not the explanation there. I think it's mainly is due to the inaccuracy of the GPS receivers. Oran Park is so narrow that with just a slight inaccuracy the route is on sand. In normal race track situations, the current receivers are just not accurate enough for analyzing the driving lines.

    So I think your data is all right, but you can send me the *-nmea.txt file for the session from \RaceChrono\Sessions\ on your memory card to tracks(at)racechrono.com, if you want me to take a look at the data.

    Also Google Maps areal photo overlays are not accurately positioned to the real location, and height difference on cause distortion on the photo since they are not photographed direct from above.
  • r1hellmanr1hellman
    Thanks aol. No need to analyse the data, your explaination is perfect. Oran Park does go up and down some hills and this could explain a bit of the problem. Also the inaccuracy of the GPS would explan the rest. I'm never shown too far off the track, only 1 or 2 metres. I also didn't realise the google earth map photo's might be taken on an angle. Thankyou for the excellent product. I have shown dozens of people so far and wil continue to do so.

    Geoffro
  • aol_of_RaceChronoaol_of_RaceChrono
    Thanks Geoffro for advertising, I'm glad you enjoy the product!
  • IcemanIceman
    edited December 2008
    Hi aol,

    First, kudos to you & team for making such a useful tool available to us. Will show appreciation via Paypal. :)

    I have tried RaceChrono for the 1st time over the weekend and exported the data to be viewed via Google Earth. The inaccuracy (in my test) is closer to 50m. How can I possibly reduce the margin of inaccuracy as I am interested in using this feature to study my 'lines'?

    Equipment used:
    Phone: Nokia E71,
    GPS Recv: Internal.

    Cheers!
  • aol_of_RaceChronoaol_of_RaceChrono
    edited December 2008
    You can probably increase the accuracy by purchasing an external receiver (try some 5 Hz model maybe), if your lines seem too choppy and inaccurate in corners. But the Google Earth photo overlays are not always accurately aligned, so your driving line could be 50 meters off anyway. On some tracks this might work though...
  • IcemanIceman
    Noted. Thanks for your quick response. Cheers!
  • MrSourMrSour
    I have also seen the same results slightly out of the track in one orientation, I suspect the google earth images are slightly out. (HTC Touch HD with Qstarz 818x @ 5mhz)

    If you want the data from an English track (Mallory) email myself a contact addy..

    Thank you for a top well produced product.
  • WestinghouseWestinghouse
    Hi
    I know this one is a bit old but I've only jsut started using Race Chrono with my mini motard today and so far I love it!! It's so easy to use and can get so much good data, even on a small 25sec lap go-kart track!
    I've just imported the track data from my phone into google earth and found an inaccuracy in the overlay to the track, is there any way you know of to edit either the google earth map or the track data to allow for the altitude difference? I'm pretty sure it's just a slight difference in scale between the two.
    Thanks
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