I didn't call you either of those things! I just didn't see the point of showing what you did as evidence. So if you were offended, then I apologize. Now on to why the times may not be the same- GPS is only accurate to about 5 meters or worse depending on the signal and many other variables. So it's approximating the end of the quarter and the speed. I don't own a dragy, but I assume it's triggered from an accelerometer when you take off. That introduces perhaps some triggering error. Given those variables, it would be very unlikely that it would produce the exact same results you'd get from breaking the lights at the beginning and end of the strip- other variables include roll-out (distance to beams on launch). I'm amazed it's actually as accurate as it seems to be from other's anecdotal observations.
Edit for the math-
So, we could theoretically be off a maximum of 32 ft in measuring the 1/4 mile. That would result in a 2.42% change. Using a 12 second quarter mile run, we could potentially be off by .24 * 12 or .29 seconds in measuring the distance. Adding in the vagaries of when the timing starts would easily explain the differences you see.
No worries, just trying to figure out why it's so far off.
I've used it in previous vehicle at milan, US131, kentucky dragway, summit, dragway 42, marion, national trails and a few other I'm forgetting. The only place it was consistently off was marion, but that is pretty far out and my phone rarely even got reception there. Every other track it was almost always within 6 hundredths. I always attributed the 6 hundredths difference to dragy starting as soon as the vehicle moves vs timing at track starting when the wheels leave the beams. The rare times I would deep stage, it would be more like 2 or 3 hundredths within the time slip.
Before I went to the track in the ST, I felt like my street runs weren't accurate but didn't know for sure. A lot of times I would be brake boosting and the rears would start spinning, so I thought maybe that was throwing it off.
At the track I've tried launching from idle just to try to rule out vehicle movement.
Three years I've had my dragy and they are typically consistent with ET's on the slips. Really just curious if anyone else had seen the same thing with their ST or maybe I should try buying a new dragy or if it is just something with their satellites?
I hate throwing money at a problem if I don't know it will fix it....but it's hard to trust my street run results when they are so far off at the track.