Speedo and avg speed via OBD

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PitrsRS
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Speedo and avg speed via OBD

Post by PitrsRS » Thu Nov 28, 2019 10:31 am

Hi Harry,

I want to ask about one thing. Sometimes I´m using speedo because it can measure avg speed. It´s usefull on roads in radar controled sections (point to point measuring). But I found a little "bug". App can´t measure avg speed with only OBD speed (in tunels). It needs GPS for it.

It´s a normal behavior?
2010 Škoda Octavia II RS TDI DSG 200HP/400Nm

HLT Grand Prix (Android) + OBDLink LX BT + XGPS160 + GoPro 7 Black
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Harry
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Re: Speedo and avg speed via OBD

Post by Harry » Thu Nov 28, 2019 10:57 am

Avg speed is derived from distance driven and time required, not some integration of actual speed values. Something like this could be done, although it requires some numeric tweaking due to the influence of data and calculation inaccuracies. Not trivial.

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Re: Speedo and avg speed via OBD

Post by Harry » Thu Nov 28, 2019 10:58 am

PS As long as the tunnel is straight, you should see proper values after leaving the tunnel again.
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Re: Speedo and avg speed via OBD

Post by PitrsRS » Thu Nov 28, 2019 12:49 pm

Ah, thanks for explanation. The tunel, where I needed most, is complicated, there are changes in elevation, corners etc. We have there 5-6 measured sections and sometimes speed limit is changed from 70 to 50 or 50 to 70 during passing (it depends on how heavy actual traffic is at the moment)

But. Distance could be calculated from speed and time, and these 2 values we have.
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2010 Škoda Octavia II RS TDI DSG 200HP/400Nm

HLT Grand Prix (Android) + OBDLink LX BT + XGPS160 + GoPro 7 Black
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