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Thread: Speedometer data not matching input data

  1. #1
    Tuner in Training
    Join Date
    Feb 2022
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    17

    Speedometer data not matching input data

    I have on the screen both speedometer and peak+base speed gauges and noticed, that their data not always match.
    Quite often peak speed is 1 kph higher than speedometer shows. In one example speedometer shows no more than 104 kph, but peak speed is shown 105 kph. To see, if it is rounding problem, I allowed showing two decimal digits by both gauges. Speedometer shows maximally 104.20 kph, peak+base speed gauge 104.51 kph. Both are rounding correctly (to 104 and 105) but why are they showing different maximum speed number? In my understanding they shoult use the same data.
    I exportred RR data to .csv, maximum speed there is 29.042 m/s = 104.5512 kph. So peak+base speed gauge is showing correct data. But why speedometer shows maximum only 104.20 kph?
    I even exported .csv file from DashWare, maximum speed there was 104.5368 kph. I used tthis .csv with RR and connected both gauges to the same KPH field (to avoid using different input data by gauges). I got the same result as RR iself shows - speedometer shows 104.22 kph, speed gauage 104.52 kph.

    In other words, peak+base speed gauge is showing correct result, just as in data file, but speedometer is showing result whch is not matching input data. What can be reason and how can be speedometer data?

  2. #2
    Tuner in Training
    Join Date
    Feb 2022
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    17
    More cloose look to the problem.
    Here are input data around maximum speed point, extracted from RR (latitude, longitude, altitude columns omitted). They look like GPS data, read from Hero 5 camera with 18Hz frequency. Video frame rate in my case is 50Hz, but can be 100Hz or eve more. That means, that for speedomeeter these data must be interpolated anyway. But for peak speed there is no real need for interpolation, with 18 Hz data frequency it's enough precise to just pick up maximum value from input data in peak area.

    Code:
    RR input data
    
    Time			Speed (m/s)
    1694506432.894000	28.867000
    1694506432.949556	28.911000
    1694506433.005111	28.951000
    1694506433.060667	29.042000
    1694506433.116222	28.940000
    1694506433.171778	28.825000
    1694506433.227333	28.776000
    Maximum speed 29.042000 m/s is 104.5512 KPH at time 1694506433.060667, which means Tuesday, September 12, 2023 11:13:53.060 AM GMT+03:00 DST. Fast control shws, that speedomeeter shows maximum speed 104.24 KPH (speedometer allows only use of integer or two decimal digits), but the peak speed gauge shows 104.512. So, here is quite a big difference by 0.3 KPH and peak speed gauge data is much closer to to initial data.

    Using these data for deeper manual check is quite inconvenient, due to need to manually synchronise 18Hz Unix timestamps with 50Hz video timestamps and do additional speed units conversion. Therefore I did the same thing with data .csv extracted from DashWare.

    Code:
    DashWare input data
    
    Timestamp	Speed (KPH)
    317.600000	103.773600
    317.650000	103.989600
    317.700000	104.162400
    317.750000	104.508000
    317.800000	104.536800
    317.850000	104.328000
    317.900000	104.025600
    317.950000	103.752000
    318.000000	103.608000
    These data are synchronised with wideo with 20Hz frequency and therefore are already interpolated, maximum speed is there 104.5368, difference with raw GPS data is less than 0.02 KPH. Peak speed gauge just picks up maximum value for time 317.800 sec and shows 104.537 KPH whch is clearly correct number.
    Speedometer output for the same time interval shows different speed values.

    Code:
    Speedomeeter indication
    
    Timestamp	Speed (KPH)
    317.600		104.19
    317.620		104.23
    317.640		104.21
    317.660		104.22
    317.680		104.21
    317.700		104.19
    317.720		104.20
    317.740		104.21
    317.760		104.20
    317.780		104.14
    317.800		104.12
    317.820		104.05
    317.840		103.98
    Highest speed shown is 104.22 KPH at time 317.620 (vs input data 104.5368 at 317.800). So speed value is different from input data, even in points 317.600, 317.700, 317.800 sec, where input data are present and where is no need for interplation. For timestamp 317.600 the difference between input data and speedomeeter indication is over 0.5 KPH. In addition the position of maximum speed point is shifted by almost 0.2 sec from 317.80 to 317.62 sec.

    That all shows, that there is something wrong with speedometer indication - these values do not match input data. I used Trans 135 speedomeeter, but with couple of other speedometers I got the same result.

    How can it be fixed?

  3. #3
    Tuner in Training
    Join Date
    Feb 2022
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    17
    The problem solved!

    Finally I got impression, that speedometer data are used with some kind of smoothing algorithm and checked again all possible settings. And Under Gauge Designer I found setting "Smooth Needle Movement" which was by default active. Switching it off solved the problem - speedometer is showing input data!

  4. #4
    Advanced Tuner
    Join Date
    Apr 2018
    Posts
    298
    Good find. I've found with certain mismatches like that, that RaceRender may have automatically chosen my GPS speed as the speed column instead of my OBD speed. So I'll change the config on the data file to choose my OBD Speed column explicitly.

    The peak speed Display Object also only sees the value that occurs during that frame at the millisecond that the frame happens to land on (even if there are 17-33 possible milliseconds that it could fall on). So if your max speed only happens for a brief instant, then it might not fall exactly where the Display Object can see it. Turning off smoothing likely helps it see the absolute value rather than an interpolation between rows.

  5. #5
    Tuner in Training
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    Feb 2022
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    Actually I was more interested in real values of speed than in exact position of maximum, therefore I noticed this mismatch between speedometer and input data. Yes, smoothing will distort mainly maximum values, but in case of asymmetric speed curve in time (like heavy brake after slow increase of speed) will also slightly shift the maximum speed point earlyer. But generally precision of GPS data interval (around 50ms) is good enough.