Harry's GPS Suite Forum

Over here the SCCA has an alternate form of autocross called "Pro Solo". This puts cars side by side on mirror image courses with a drag race start.

Normally i'll mark a start and finish line for an autocross course. Usually you cross the start line at some speed, so a normal trigger works well. I've never had any luck with the standing start trigger.

I tried to mark the start and finish lines for both courses. Usually the lap timer will complain when I add more than one trigger to a course. This time it just refused to set the second start line trigger. The two start lines are only about 6m apart.

To work around that I put in one trigger between the two start lines, a few metres in front of the line. This did work reliably to trigger the timer. I also marked the two finish lines. This worked relatively well to do data acquisition.

Next I wanted to compare runs, but I find that the lap timer will not compare runs from one course to the other. When I try that, the data shows up for comparison, but the time deficit shows up steadily rising. The time deficit is the most massively useful feature of the lap timer for working out where you gain or lose time, this makes it less useful. I was interested in comparing how I was doing on the different course. Comparing a 36.5s run with a 35.3s run on the other side, the time deficit just climes to about 33s.

I thought the lap timer did the comparison on a time vs distance traveled basis, so I can't work out why its behaving like this.

Hi,

Comparison works location based. This means for any current position, LapTimer calculated the matching position on the reference lap and compares the tim stamps. So in case the two tracks are parallel, it should work. In case the tracks are mirrored (i.e. #1 going to to the left when #2 is join to the right) it will not. The later would work for a distance based approach. As distance is not very accurate, that approach proved to be inferior (I had that initially).

- Harry

Btwyx,

When I did a ProSolo earlier this year, I would get a start on one course, but it didn't stop until I finished the second course. That wasn't terribly useful. Even though the courses are supposed to be mirror images, there are always going to be differences, the surface, if nothing else. Unless you used high precision surveying equipment to set the cone positions, it's unlikely that they would be true mirror images. As a result, I'm not sure that comparing data between the left and right courses is going to tell you much.

gplracerx wrote:Btwyx,

When I did a ProSolo earlier this year, I would get a start on one course, but it didn't stop until I finished the second course. That wasn't terribly useful. Even though the courses are supposed to be mirror images, there are always going to be differences, the surface, if nothing else. Unless you used high precision surveying equipment to set the cone positions, it's unlikely that they would be true mirror images. As a result, I'm not sure that comparing data between the left and right courses is going to tell you much.

I don't do many Pro Solo's but I agree, like comparing two different tracks, why would you?