User manual

6 Atmosphere and Instruments
XCSoar maintains an internal model of the atmosphere based on
statistics gathered from the flight path and other instruments con-
nected to the Pocket PC device. These statistics and measurements
are approximate and the weather can on some days change rapidly.
The pilot should at all times keep observing the weather. In partic-
ular, when out-landing in fields, the pilot should look for indicators
on the ground to confirm wind strength and direction.
6.1 Variometer
(Landscape display mode only)
A needle-dial style display shows the variometer measurements.
The gross variometer reading drives the main arrow on the dial,
and in the center of the dial the instantaneous measurement is
shown as text. Additionally, speed command arrows (chevrons)
appear above or below the gross variometer measurement. Chevrons
pointing up indicate slowing down is recommended. Chevrons
pointing down indicates that speeding up is recommended.
The vario gauge is customisable as to what is displayed along with
the gross value, see the Configuration section for more details.
When the averager is displayed, the value shown is the average
gross climb rate over the previous 30 seconds when in circling
mode, and the netto (airmass) vertical speed over the previous 30
seconds when in cruise mode.
When an intelligent variometer is connected to XCSoar, the nee-
dle displays data from the instrument; otherwise it produces vari-
ometer estimates based on GPS vertical speed, which is slow and
uncompensated for aircraft total energy.
The MacCready value, bugs and ballast, optimum speed to fly and
wind data are transferred between XCSoar and supported external
intelligent variometers. In the ideal setup, both XCSoar and the
variometer have a consistent perspective on the flight at all times;
and that by adjusting the MacCready setting on one device should
be kept in sync with the other, by the software and to not require
additional input from the pilot.
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