Speed - This is a calculated GPS value Magnetic compass heading - A solid-state geomagnetic (compass) sensor provides magnetic heading Course over ground - Magnetic Heading can be changed to show Course over Ground Heel angle - Simple visual indicator of heel angle which is logged with the other boat data and provides excellent post-race analysis V2 Prostart - Key Improvements: High visibility in all conditions A bonded Gorilla® Glass display with sharp white on black digits shows up crystal clear, even using polarised sunglasses. A user selectable white / red LED backlight takes care of night sailing or other low light situations.