Poor resolution of OBD2 data

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orthojoe
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Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 12:39 am

Harry,

I recently switched from RaceChrono pro to your laptimer and I am still trying to figure out a few issues.
In terms of my 'hardware', I am using emprum ultimate GPS receiver and Kiwi Wifi OBD2 on a Porsche Boxster Spyder (3.0Hz OBD2)

1) The rpm gauges on the laptimer appear to have a slight delay from what is going on real-time. Can this be improved with a certain setting?
2) Exporting the data to .csv format for Trackvision: throttle position is in hundredths (0.1,0.5,1) instead of full integers (10,50,100). In future updates, can the exports have an option to be specific for trackvision use?
3) The displayed data on trackvision is jagged/juddery/not smooth. It seems the resolution is not fine enough for a good video. I'm not sure why this would be since the hardware between RaceChrono Pro and what I am using with your laptimer is not significantly different in terms of resolution. Is there something I can do to improve this?

Thanks again, Harry.
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Harry
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Re: Poor resolution of OBD2 data

Post by Harry » Sat Jan 14, 2012 12:57 am

Hi,

Update rates strongly depend on the car's bus. It is getting fun when the rate is going beyond 8Hz. Below, the realtime display always looks a bit deferred. I'm aware of several optimizations I could apply to LapTimer's OBD communication resulting in better rates. I will most probably implement this in a future version.

I'm not an expert on TrackVision. From what you write, it does not interpolate values per frame. For LapTimer, I introduced this early as video quality is greatly improved. As TrackVision is a pretty specialized product, I would expect them to have this too. Maybe you contact them, there is probably a setting somewhere.

Finally, with LapTimer v15, you will not use any external overlaying tool any more ;-)

- Harry
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orthojoe
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 1:36 am

The confusing thing is the datalogging I achieved with RCpro did not result in poor resolution. The RCpro used wireless OBD data as well. Here is a sample of my old videos on using RCpro data:
http://youtu.be/3Itd5TVyaX8
http://youtu.be/_dE1jMcmmOc

The resolution should be same unless RCpro does interpolation prior to exporting to .csv?

It is exciting to hear that v15 will have a great video overlay tool, but the iphone camera is not ideal for recording video. A gopro or something similar is better. External software like trackvision allow for different positioning and gauges to be laid over gopro video. I like overlaying data on gopro video rather than the iphone video.
orthojoe
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 1:56 am

Harry,

I am examining the .csv output file from your software. Why is there a space in between each row? It's interesting because it seems like the empty spaces are meant for interpolated data?

I examined the .csv out from my racechrono and there are no spaces between rows and there is data every .1 second vs the data output from your software is every .2 seconds

Can I email you the .csv files for you to compare and take a look at?
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 2:24 am

For reference, the gps receiver in my old RCpro unit ran at 5hz as well
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 5:31 am

Harry, I downloaded dashware and the data does not appear smooth on dashware either. I did a close comparison between the .csv data on HLT vs RCpro, and I believe the main difference is that HLT provides data every 0.2 seconds, whereas RCpro provides data every 0.1 seconds. As a result, there is only 1/2 as many data points, hence the poorer resolution.

Is this a limitation of the hardware, or could a future update provide data every .1 seconds?
Why is there an empty row between every data point on the .csv file? It seems like the empty row is the lost 0.1 second of data?

It is also interesting that video generated off of the iphone with your software does not seem to skip every other 0.1 seconds. Perhaps there is an issue with the exporting of data to .csv format and we are missing one out of every 2 data points somehow?

I've attached a screen print of my .csv. Notice the space between each line

***One more issue: I can only export a trackvision/dashware .csv one lap at a time. Is there a way to export an entire session? If I select an entire day, the option for trackvision/dashware .csv export fades out and is no longer an option...
Attachments
screencsv.jpg
screen shot of my .csv trackvision export. Note the space between each line. Data points are only every 0.2 seconds, not every 0.1
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Re: Poor resolution of OBD2 data

Post by Harry » Sat Jan 14, 2012 10:33 am

Hi Joe,

Starting with the skipped line - this is about different line breaks on different operating systems. Older LapTimer versions added a CR and a LF character to the end of each line. I believe starting with 14.4 (didn't check, need to search the history) only a LF is added. Good editors are able to handle all kinds of line break combinations, your Excel import obviously converted the CR and the LF in a line break each resulting in the empty lines. For Track vision import, either it is able handle different line breaks, or you need to convert it to your platform's (Windows, I assume) standard first. Please check your LapTimer version too, 14.4 has just been released. As long as values are not falling down to 0 every seconds data set, I assume this is not an issue at all and TrackVision skips this.

The main difference seems to be the 'update rate' of the export. As your GPS delivers 5Hz, LapTimer delivers a dataset every 0.2 seconds. For 1Hz devices (or the internal GPS), it will have one line each seconds. You said the RCPro delivers a row every 0.1s - this simply means it does 'a little bit' of interpolation during export already. Looking into the sample videos, it is obvious for me TrackVision does not apply interpolation. Although the overlays look o.k., they are bumpy compared to what LapTimer generates. Reason is that LapTimer calculates an interpolation for every frame - which is 30Hz for iPhone videos. So even adding a seconds line per data set is actually not really good, it would be best to have a lot more.

To work around this, you may consider the following: simply import data from LapTimer into excel. Interpolate the rows using some Excel macros yourself. For 0.1s is it pretty easy as you can use the empty rows and add "=AVERAGE(cell above; cell below)". This will work for numeric fields at least. In case you want a really great video, add 5 interpolation lines for each row (which is a little more tricky - send an email if you need assistance here). Finally, export the Excel to CSV again.

Hope that helps.

- Harry
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orthojoe
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 3:49 pm

Thank you for the quick responses, Harry. It is very much appreciated. I do have version 14.4. As you predicted, trackvision skips the empty rows of data and is able to utilize the .csv files. I had a feeling RCPro did 'a little bit' of interpolation during export already. Is there anyway that future updates can include your interpolation into the exports? This would be of ENORMOUS value to me.

I would be interested in learning how to interpolated the rows using excel macros. However, to copy/paste "=AVERAGE(cell above; cell below)" into every single empty row individually would be impossible to do with the shear amount of data. Is there an easier way to do this? I would very much like to learn more about how to do this. Where can I find your email?

Lastly, what are your thoughts on this issue:
I can only export a trackvision/dashware .csv one lap at a time. Is there a way to export an entire session? If I select an entire day, the option for trackvision/dashware .csv export fades out and is no longer an option...

Thank you so much for your time, Harry
-Joe
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Re: Poor resolution of OBD2 data

Post by Harry » Sat Jan 14, 2012 5:19 pm

Hi,

Thinking about interpolation based on the the LapTimer CSV it is probably better to do it using a AWK script. I'm sure there is someone around who can do this. Indeed, in Excel, it would require you to add some automation to add the macros in. Please understand that I cannot spend too much time on adding functions that should actually be in specialized programs like TrackVision and DashWare. I happily provide the basics, everything else needs to be done by someone else. Thanks for your understanding.

- Harry
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orthojoe
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Re: Poor resolution of OBD2 data

Post by orthojoe » Sat Jan 14, 2012 8:07 pm

Harry, I understand your point of view. However, please consider that the value of your software is significantly increased when it can be used with programs such as trackvision. Since your program already interpolates data to perform it's own video overlay, is there no way to export this?

one last issue:
I can only export a trackvision/dashware .csv one lap at a time. Is there a way to export all laps to .csv? If I select all or entire day, the option for trackvision/dashware .csv export fades out and is no longer an option...
Attachments
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trackvision/dashware export is unable to be activated
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