The utility of quack is greatly enhanced since the cancellation of the artifical error generation (Selective Availability).
| New! Prototype quack-generated MPEG of 50 laps of the Nordschleife, with a variety of drivers, vehicles and conditions. |
In our first installation on the ZXR750, we had a
Garmin GPS III
under the rear seat, with the standard antenna mounted externally
on the left sidepanel. You can see the antenna in the
big version of this
picture.
Housing the GPS under the rear seat proved to be quite
inconvenient, so in the second version, we mount it on the
fairing stay, where the rider can see and manipulate it.
The external antenna is not required as the GPS can
easily see through the bike's screen, althought it does benefit
from the active antenna.
(See GPS fitment to the new GSX-R on
Adam's GSX-R GPS Bracket)
(big picture 120kb).
Now SA is turned off, the vastness of the Nordschleife
makes for excellent track logs with quack.
Quack works best with data at this scale.
Under SA, The fixed size of the errors meant that the bigger you go, the
smaller the significance of the error.
Some of these laps had comparatively coarse track log configurations in the GPS-III with a standard antenna, yet at this scale they look pretty good.
In the examples below, the overlay of the raw track logs on circuit maps shows the effect of the uncorrected position errors.
The errors caused by GPS selective availability
are clearly visible in these laps.
These laps of Donington show even more variation.