What exactly do these do?
It's kind of like a really kick-ass odometer, but that's underplaying them.
They can be calibrated, and can receive signals from various probes. You can zero them easily, with each manufacturer offering a number of accessories such as foot pedals or hand controls.
They can provide performance data, as well, but are mainly useful in environments where a driver and co-driver must keep track of precise time and distance data in difficult and quickly changing conditions in order to win a race against a clock, rather than directly against competitors. A number of features are present to help accomplish that goal.
The things are damned useful in "dead reckoning" navigation because of their precision and simplicity.
Very nice to have.
You'd need at least two stop-watches, two odometers, a Scangauge, a clock, and a number of calibration tools to match the capabilities of even the most basic rally computer.
Cheers,
Kennith
