Date in logs, accelerometer sensitivity

CoreForce

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I'm looking into the raw data of my 805, and after playing a while with it, I stumble on two things.
- the dates in the log are sometimes starting at 1980 but come to current date after a while
- the sensitivity of the accelerometer appears to be "cheap"

First thing probably is due to an empty battery after long rest (weeks)? If one checks the excerpt from a recent log, this is starting in a garage, no GPS reception at the beginning. But still without a lock the date changes first from 060180 to 090180, only some seconds later to the correct date 140916. I would assume this is aligning with GPS date information from first satellites received? Only issue is that this makes alignment of GPS data with video footage a bit complicated. The video file has correct timestamps for create and modified date, interestingly enough (video file create date is 140916,074140, a timestamp that is never seen in the logs).

Second thing is the G-Force sensor readings. Though the car is in total stand still, the readings are not quite aligned to zero or gravity, are they? Also the values appear to shift a bit. What I see later when driving is the readings are not very solid, values are kind of swinging significantly between left and right when driving on a straight line. Seems to me the accelerometer is really just good for crash detection (huge spike detection) but not for general purpose readout?

Any experience to share would gladly be appreciated.

Log from first seconds of startup from inside a garage
V,050180,235949.003,,,,,0.00,-04.29,-34.30,-03.68;
V,050180,235950.003,,,,,0.00,-03.68,-34.30,-03.06;
V,050180,235951.003,,,,,0.00,-04.29,-34.30,-03.06;
V,050180,235952.003,,,,,0.00,-04.29,-34.30,-03.06;
V,050180,235953.003,,,,,0.00,-04.29,-34.30,-03.68;
V,050180,235954.003,,,,,0.00,-04.29,-34.30,-04.29;
V,050180,235955.003,,,,,0.00,-04.29,-34.30,-03.68;
V,050180,235956.003,,,,,0.00,-04.29,-34.30,-03.06;
V,050180,235957.003,,,,,0.00,-04.29,-34.30,-03.68;
V,050180,235958.003,,,,,0.00,-04.29,-34.30,-03.68;
V,050180,235959.003,,,,,0.00,-06.74,-34.91,-03.68;
V,060180,000000.003,,,,,0.00,-03.68,-34.30,-03.68;
V,060180,000001.003,,,,,0.00,-04.90,-33.69,-03.68;
V,060180,000002.003,,,,,0.00,-04.90,-34.30,-03.06;
V,060180,000003.003,,,,,0.00,-03.06,-33.08,-04.29;
V,060180,000004.003,,,,,0.00,-06.12,-33.69,-04.29;
V,060180,000005.003,,,,,0.00,-04.29,-34.30,-03.68;
V,060180,000006.003,,,,,0.00,-04.90,-34.30,-04.29;
V,060180,000007.003,,,,,0.00,-02.45,-34.91,-03.68;
V,060180,000008.003,,,,,0.00,-03.06,-33.69,-05.51;
V,060180,000009.003,,,,,0.00,-01.23,-36.14,-04.90;
V,060180,000010.003,,,,,0.00,-03.68,-33.69,-02.45;
V,060180,000011.003,,,,,0.00,-04.29,-33.69,-01.84;
V,060180,000012.003,,,,,0.00,-04.90,-35.53,-04.29;
V,060180,000013.003,,,,,0.00,-03.68,-33.08,-05.51;
V,060180,000014.003,,,,,0.00,-03.68,-34.30,-03.06;
V,060180,000015.003,,,,,0.00,-03.68,-33.69,-04.29;
V,060180,000016.003,,,,,0.00,-06.12,-34.30,-04.29;
V,060180,000017.003,,,,,0.00,-06.12,-34.30,-01.84;
V,060180,000018.003,,,,,0.00,-04.29,-39.20,-06.12;
V,060180,000019.003,,,,,0.00,+00.00,-33.08,-01.84;
V,060180,000020.003,,,,,0.00,-04.29,-33.08,-06.12;
V,060180,000021.003,,,,,0.00,-04.90,-30.63,-09.80;
V,060180,000022.003,,,,,0.00,-06.12,-34.30,-00.61;
V,060180,000023.003,,,,,0.00,-04.29,-36.14,-05.51;
V,060180,000024.003,,,,,0.00,-04.90,-34.91,-04.90;
V,060180,000025.003,,,,,0.00,-03.06,-34.30,-06.12;
V,060180,000026.003,,,,,0.00,-02.45,-34.30,-06.12;
V,060180,000027.003,,,,,0.00,-03.06,-34.91,-03.68;
V,060180,000028.003,,,,,0.00,-03.06,-34.91,-03.68;
V,060180,000029.003,,,,,0.00,-06.74,-36.14,-04.90;
V,060180,000030.003,,,,,0.00,-04.90,-35.53,-03.68;
V,060180,000031.003,,,,,0.00,-04.29,-34.30,-03.68;
V,060180,000032.003,,,,,0.00,-05.51,-36.75,-04.29;
V,060180,000033.003,,,,,0.00,-06.74,-34.30,-03.06;
V,060180,000034.003,,,,,0.00,-06.74,-35.53,-03.06;
V,060180,000035.003,,,,,0.00,-06.74,-34.91,-05.51;
V,060180,000036.003,,,,,0.00,-06.74,-33.08,-05.51;
V,060180,000037.003,,,,,0.00,-06.12,-35.53,-05.51;
V,060180,000038.003,,,,,0.00,-04.29,-34.91,-06.12;
V,060180,000039.003,,,,,0.00,-04.29,-34.91,-06.74;
V,060180,000040.003,,,,,0.00,-03.06,-35.53,-06.12;
V,060180,000041.003,,,,,0.00,+01.23,-34.91,-06.12;
V,060180,000042.003,,,,,0.00,-01.23,-34.91,-04.29;
V,060180,000043.003,,,,,0.00,-05.51,-34.91,-04.90;
V,060180,000044.003,,,,,0.00,+03.68,-33.69,-03.06;
V,060180,000045.003,,,,,0.00,-00.61,-35.53,-03.06;
V,060180,000046.003,,,,,0.00,-03.06,-34.91,-01.23;
V,060180,000047.003,,,,,0.00,-04.29,-33.08,+00.00;
V,060180,000048.003,,,,,0.00,-11.03,-35.53,-01.84;
V,060180,000049.003,,,,,0.00,-16.54,-39.20,-01.84;
V,060180,000050.003,,,,,0.00,+01.84,-34.30,-04.29;
V,060180,000051.003,,,,,0.00,-03.68,-35.53,-06.74;
V,060180,000052.003,,,,,0.00,-02.45,-34.91,-07.35;
V,060180,000053.003,,,,,0.00,+00.00,-36.75,-12.25;
V,060180,000054.003,,,,,0.00,+00.00,-34.30,-02.45;
V,060180,000055.003,,,,,0.00,+01.84,-33.08,+07.35;
V,060180,000056.003,,,,,0.00,-01.84,-37.36,+03.68;
V,060180,000057.003,,,,,0.00,-05.51,-33.69,+01.84;
V,060180,000058.003,,,,,0.00,-07.96,-34.30,+00.00;
V,060180,000059.003,,,,,0.00,-00.61,-36.14,-04.90;
V,060180,000100.218,,,,,0.00,+01.23,-34.91,-04.29;
V,060180,000101.218,,,,,0.00,+03.68,-36.14,+00.00;
V,060180,000102.218,,,,,0.00,+05.51,-34.91,-01.84;
V,060180,000103.218,,,,,0.00,+04.90,-33.08,-01.23;
V,060180,000104.218,,,,,0.00,-07.35,-33.08,+07.35;
V,060180,000105.218,,,,,0.00,-03.68,-34.91,+00.00;
V,060180,000106.218,,,,,0.00,-05.51,-35.53,-06.74;
V,060180,000107.218,,,,,0.00,-06.12,-33.69,-01.84;
V,090180,074216.092,,,,,0.00,+01.23,-36.75,+01.84;
V,090180,074217.092,,,,,0.00,-07.96,-35.53,-02.45;
V,090180,074218.092,,,,,0.00,-03.68,-34.91,-03.06;
V,090180,074219.092,,,,,0.00,-09.19,-32.46,-05.51;
V,090180,074220.092,,,,,0.00,-11.64,-34.91,-04.90;
V,090180,074221.092,,,,,0.00,-14.70,-37.98,-02.45;
V,090180,074222.092,,,,,0.00,-03.68,-36.75,-03.68;
V,090180,074223.092,,,,,0.00,-03.06,-34.91,-03.68;
V,090180,074224.092,,,,,0.00,-09.80,-33.69,-03.06;
V,090180,074225.092,,,,,0.00,-06.12,-33.69,-04.29;
V,090180,074226.092,,,,,0.00,-09.19,-37.36,-04.29;
V,090180,074227.092,,,,,0.00,+01.23,-32.46,-03.06;
V,090180,074228.092,,,,,0.00,-01.23,-34.30,-02.45;
V,090180,074229.092,,,,,0.00,-07.96,-34.91,-04.29;
V,090180,074230.092,,,,,0.00,-06.12,-36.75,-04.29;
V,090180,074231.092,,,,,0.00,-04.29,-36.14,-03.68;
V,140916,074232.092,,,,,0.00,-02.45,-36.75,-03.06;
V,140916,074233.092,,,,,0.00,-02.45,-35.53,-01.84;
V,140916,074234.092,,,,,0.00,-07.96,-35.53,-03.06;
V,140916,074235.092,,,,,0.00,-05.51,-36.14,-02.45;
V,140916,074236.092,,,,,0.00,-03.68,-36.14,-04.29;
V,140916,074237.092,,,,,0.00,-00.61,-34.91,-03.68;
V,140916,074238.092,,,,,0.00,-01.84,-34.91,-04.90;
V,140916,074239.092,,,,,0.00,-02.45,-35.53,-03.68;
V,140916,074240.092,,,,,0.00,-08.58,-35.53,-02.45;
V,140916,074241.092,,,,,0.00,-01.84,-35.53,-02.45;
 

jokiin

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Too many ¯\_(ツ)_/¯
the initial date reset is likely a low or failing RTC cell in the GPS, will still work but will be a bit slower initially if it has been sitting around

if the G-Sensor starts reading all zeros suggest grabbing onto something solid before you float off into deep space ;)
 

DT MI

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More than my wife thinks I need.
...if the G-Sensor starts reading all zeros suggest grabbing onto something solid before you float off into deep space ;)
:D
 

lacibaci

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The GPS behaves exactly the same way on my 0903. Not surprising given Meg is using the same module.
How long does it usually take for the initial lock? Last time I checked there was actually a small capacitor used instead of a button cell battery. This makes it more resistant to heat but slower to get the initial fix since after couple of hours the module must do a cold start.
I don't think there is much you can do about that.
Don't know much about the sensors...
 

jokiin

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Too many ¯\_(ツ)_/¯
The GPS behaves exactly the same way on my 0903. Not surprising given Meg is using the same module.
How long does it usually take for the initial lock? Last time I checked there was actually a small capacitor used instead of a button cell battery. This makes it more resistant to heat but slower to get the initial fix since after couple of hours the module must do a cold start.
I don't think there is much you can do about that.
Don't know much about the sensors...
warm start is normally about 20 minutes and can realistically only be used up to about 4 hours max as the Ephemris data becomes invalid after a while anyway so depending on the type of GPS used there may not be a need to have anything saved longer than this for warm start purposes, Almanac data though can be up to 6 months worth of info so ability to hold this detail longer can still be useful for cold start purposes
 
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CoreForce

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Thanks, it takes me around 4 minutes until I get the GPS fix, would assume this is normal.

G-Force reading are last three values of a row. For a car parking on even ground I would appreciate on 2 axis to read zeros or something close at least, right?
 

jokiin

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Too many ¯\_(ツ)_/¯
4 minutes is a bit slow but windscreen type can make a difference

G-Sensor will always detect some movement in each direction, that's normal
 
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CoreForce

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I've rendered a short video with some extra gauges to illustrate my problem with the variance in readings I get.

 

thancam

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I've rendered a short video with some extra gauges to illustrate my problem with the variance in readings I get.

what software did you use to make this video ? :)
 
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CoreForce

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what software did you use to make this video ? :)
I'm on a Mac so I can't use the Mini's Video app.
Therefore I wrote myself a software to convert the log data into GPX format and then use the Garmin VIRB app to render it with the video files.
 
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CoreForce

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Wanted to provide a quick update on the topic. I'm doing some averaging and weighting on the accelerometer
to get them smooth and now I'm happy with the results. Maybe it will need some fine tuning but so far it's ok for me.
See a sample how it looks like right now, on the same position as with the last video and also some curves further down the road.


Also the metering on height is working now on a level that looks somewhat acceptable to me and I managed to integrate a track-animated map along with the video footage.
 

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