Harry's GPS Suite Forum

HI,

I would like to figure out if there is something wrong with my setup, or with exporting the data from the lap timer, or with google earth or a combination of them. When I export a lap out of the lap timer and see it on google earth, the lines are off the track. Can anyone help? I can mail you the google earth file if that helps.


For reference, I run a XGP150 with an iPhone. Also, this is Thunderbolt Track in NJMP, USA.

Hi,

That's a combination of GPS accuracy limits and inaccuracy of the satellite pictures. The perspective adds some misplacement in addition as all the dots 'fly' above or below surface (vertical inaccuracy like horizontal above). So looking from the side instead of top down adds an additional error. To show plots from consumer level GPS "on track", the left and right limits of the track need to be known and a special (complex) "fit" transformation needs to be applied to the raw data.

- Harry

Is the GPS simply not accurate enough? I am also not seeing any acceleration or lean angle data on the video overlay. Is that related or am I doing something wrong with the GPS?

To get a proper lean angle for motorbikes, lateral acceleration needs to be calculated first. You should actually have been prompted when starting the overlay but probably skipped this step? Anyway, to repeat that step, enter the lap's details, revert your video back to the raw / original one, press the "Calculate" button, and select Lateral Acceleration. Now, smooth the lateral forces as much as necessary using the slider. Once this is done, repeat the overlay. Btw. to get valid lineal acceleration for a motorbike, you need to have the phone mounted in a somewhat upright position, not completely flat.

- Harry

Got it - thanks Harry.