Has anyone compared the speed channels from their AIM dash and noticed a substantial difference between the GPS and the ECU speeds?

On my car (AIM MXS 1.2, SADEV trans), the "SRF SPEED" channel consistently reads about 2% higher than the "GPS Speed" channel. I'm wondering why that might be and I'm looking for advice on what configuration I might need to do.

I'd prefer to leverage the SRF SPEED, as it's less noisy and I expect more precise (although not necessarily more accurate) than what comes from the GPS. For comparing my own laps to each other, accuracy isn't important, as long as the data is repeatable. However, comparing my data to other drivers (as in, "Hey Craig, what's your minimum speed through turns 1 and 2?"), accuracy is at least somewhat important. I suspect that my GPS is giving me a more accurate value, at least relative to the other cars that I tend to lap with -- I'm not running 2MPH faster than they are, in spite of what my ECU is reporting to the dash logger.

Anyone else have this in their car, or have any thoughts on what setup/config step I might need to do?

Craig,
I would suggest you contact Robbie at AIM, Lake Elsinore,CA. He is very knowledgeable. (951)674-9090.

I have seen similar difference in GPS Speed & SRF3 SRF Speed. However, I am seeing , usually,only 1-2 MPH difference. Then when I view other track locations, the speed is exact.

Now with the new SADEV, I am sure we will have another set of figures coming from the SADEV to SRF ECU to AIM.

all you can really do is optimize your GPS setup (good view down to horizons, use a small 6-8" ground plane to minimize multipath reflections, etc.). Also GPS-09 is a good upgrade from the GPS-08 (better GPS reception section and also records at 25Hz rather than 10Hz). Monitor the number of satellites in view and GPS position accuracy (in your recorded AIM data).

You may also consider adding two front wheel speed sensors, as your dash can handle that. Then you can fine-tune the indicated speed using the tire diameter in your AIM configuration, and also see incipient lockups under braking.

I have a front and rear AIM smarty cam set up. I would like to be able to sync the videos and have the "rear" cam video play in overlay on the front video (pic in a pic so to speak) as though it was a rear view mirror. Can any of you high tech people direct me to a intuitive software program/video editing program that I can use to do this?
I had a STACK system prior to 2014 that did this easily, so I can't understand why AIM hasn't adopted this old technology.