Harry's GPS Suite Forum

Using HLT on an iPhone 3GS, windscreen mounted, with internal GPS.

After exporting a video tonight and overlaying just GPS data, I noticed that the speedo would sometimes be slow to update to the current speed, or remain fixed on one speed before very quickly catching up with the actual speed.

It's not out of sync, it's like it's having a GPS read problem.

This drive was outside of the cities. How can I check if it's a GPS problem, or could it be a video overlay issue?

Hi,

Assuming you are not using an OBD in parallel (which is used for speed display as long as connected), it is about GPS quality. The 3GS GPS is not very sensible and most probably loses the fix from time to time. Please check the update rate in the GPS View, it should be around 1Hz. In case it is below, this is the issue.

You may either check if you find a better place to mount or go for one of the external GPS options listed here: www.gps-laptimer.de/Compatibility.html

- Harry