Harry's GPS Suite Forum

Hey gents,

I purchased this app for autocross. I am only using my phone currently with no external devices. I went out to a few parking lots today to try to test the app. I only tried the “new track” feature as I would pick a point and then drive a few loops around the parking lot. I made certain the phone was aiming the direction I would pass (held as if I was taking a video of the “finish line.”) I tried both vertical and horizontal positions during the finish line marking. I did manage to get the app to trigger a few times, (3/20 or more) but it would usually only start or catch one lap before starting to miss the trigger. I checked and I had no red flags in the health check.

-I see there are a lot of predesigned maps for this app. Because they are predesigned are they more accurate than using the create track feature?
-Would an externally linked GPS device help me resolve this issue or is that unlikely the source of the problem?
-Does the orientation of the phone (vertical or horizontal) have any impact on marking the starting point of your track/autocross?

Thanks for any help.

Orientation does not have a direct effect in trigger detection. The GPS antenna will work better in one direction, but this depends on the smartphone model and cannot be answered in general. From what you describe, I assume there is either a problem with low GPS precision, or the direction set for passing the s/f is off or not set. To get good GPS accuracy, please use a mount like shown in illustration #3 of LapTimer's Quick Reference. To verify the trigger setting, select one of the laps that worked from Lap List and scroll down to Data Recordings. Select the row "Preview" and habe a look into the line driven and the trigger position and direction.

- Harry

Elemento1991,

I purchased this app for autocross.

You can't do autocross at all well without at least a 5Hz GPS. The 1Hz, heavily filtered, phone GPS is not good enough. It also tends to drift. That's usually OK for a race track where you can use a wide detection corridor, not so much for autocross.

I use a Dual XGPS160, which works reasonably well most of the time. The GPS calculates direction, but only when moving. I don't think the magnetometer in the iPhone is good enough either, even if Harry's were able to use it. There are no predesigned maps for autocross. If there is someone else using Harry's at the event, you can share a map by email but you have to set a start and finish each time. If you use the same venue, you will need to purge the POI's for previous events, as they're stored by location.

I also recommend setting the accelerometer update rate to 100Hz for autocross. The default setting of 30Hz is meant for a 1Hz GPS, I think. Also, you need to be careful about POI's not overlapping. Setting a direction helps with that, but that also sets a wide corridor detection. That's probably too wide for autocross, so that may need to be modified as well.