zzyzx

The other day I ran a test day at Willow Springs using both my AiM EVO4 datalogger mounted in my car, and my AiM Solo.
You can see that there are big differences between the two. This is the same lap.
At its worst, there is an 8 mph difference in speed, and a 0.4 difference in time.
So, if there is this much disparity between AiM datalogger systems, that would make it useless to compare data with another driver.
Is there something wrong with either my EVO4 or my Solo?

Matt Romanowski

Try doing a GPS lap insert on both sessions to make sure they are using the same start/finish coordinates and see if that changes anything.

ProCoach

Having sold 140+ EVO4's and over 500 Solo DL's, and often used them on the same car at the same time WITHOUT difficulty, there's something off.

Either what Matt says or an issue with the unit itself.

I can't tell from your export. Can't see overlaid lines.

zzyzx

I just checked the GPS positional accuracy. With the EVO4, it's consistently less than 1 meter. With the Solo, it's several meters.

I think I know what the problem may be. I have the Solo mounted on my fire extinguisher on the floor. (That was the only metal that was easily accessible.) It may be moving around, or it may not be getting a good satellite signal. Next time, I will try mounting it on the windshield with a suction cup.

I'll update what I find out next week. Thanks for the suggestions so far.

Matt Romanowski

That could certainly be the cause.

Spyerx

FWIW when I run a transponder the AIM SOLO DL is w/I a couple 100's of the MyLaps system. so I've found it to be very accurate for lap times. GPS at the tracks I go to is good, but big willow you definitely want it on the dash as the hillside topography can mess with the reception a bit (you can see this in the log files on the Solo, the number of GPS tracked).

Matt Romanowski

His situation is a bit different. It will get the satellites, but the signal bounces around in the car diluting the accuracy. Since GPS is based on time and position, the extra bounces throw of the accuracy.

jwasilko

One of the channels logged is the number of visible satellites. Is it the same for both units?

ProCoach

Matt Romanowski

Where he had it mounted, it will show a good sat count but have poor accuracy.

zzyzx

So I went back to Willow and this time I mounted the Solo with a windshield suction-cup mount.

The print out attached shows a comparison of the same lap driven in my '03 Z06. Although the lap time seems like it's dead on (1:30.285 and 1:30.280), when you look at the data, there are huge differences--as much as 10 mph and a half a second. This would of course make data comparison useless.

Any ideas? I see this as a big issue if we can't rely on AiM data to be consistent between data loggers.

mglobe

It looks lie the two devices are using different start/finish coordinates. It's not a speed difference, it's a distance difference.

Matt Romanowski

Agree with Mike. Shift one lap or do a gps lap insert to align start finish and check again.

zzyzx

With the Solo data, I tried using the "Use Start/Finish from GPS Track Database," but I get an error message saying "Sorry, irrecuperable GPS data. Impossible to execute operation. Error in Master Clock for lap N170078"

On one part of the EVO files (I had downloaded and then cleared my first session, then downloaded and cleared all the other sessions later, so I have two files), it allows me to do this operation. But on the other file, when I try to do this, it does not show the GPS map (just some squigly lines).

Thundermoose

Send your two files to Matt or Peter and see what they discern.

I usually use the other file as reference when doing GPS lap insert as opposed to what you did.