Actually the app starts tracking when the GPS signal is received.
There is not any feature to remove the red tracking line (in our TODO list)
The only way is to quit and relaunch the application.
- double click the Home button, multitasking bar opens (displaying recently used apps)
- swipe left or right and locate the app you want use (for example Marine US)
- tap and hold icon in multitasking bar for a second or two until it starts to jiggle : you'll see a little minus badge in top left corner.
- now, you just click that "minus" and app is "really closed"
- double-click the Home button and try opening the app again