A barograph or device incorporating a barograph must operate throughout the flight. The barogram so produced must provide indisputable verification of flight continuity (see 4.3.4) and of all altitudes critical to the soaring performance. The device may record parameters in addition to barometric pressure and time if it is suitable for the purpose (see 4.4). If data is recorded at intervals, the sampling rate setting must be no slower than once per minute.
For flight recorders, timing and pressure altitude data will be taken at the boundary of the observation zone interpolated between the times of valid fixes; or for a start or finish, this data may be taken from the fix in the observation zone which is most favourable to the pilot. See Annex C para 9.2.
The landing location must be certified by one or more of the following:
a. By an OO arriving soon after the event and there is no doubt about the position of landing or,
b. By two witnesses (see 5.2.3d),
c. By position data from a flight recorder (but see also 4.6.4a(ii)).
Where the soaring performance is required to end at a declared finish point, the goal will be achieved if:
a. The landing point is within 1000 metres of the declared finish point or,
b. If the finish point is an airfield, the landing is within the boundaries of the airfield or,
c. Satisfactory evidence is produced showing that the glider was in the observation zone and within 1000 metres of the finish point,
d. A finish line at the goal is crossed.
e. For any type of closed course goal flight where a start other than release or a start line is used, the glider must exit the start point OZ within 1000 metres of the declared start point.
There must be evidence that the glider did not land or a means of propulsion was not used during the claimed soaring performance. An interruption in the barogram data will not compromise proof of flight continuity provided that the OO and NAC are convinced no critical data is missing and that the evidence for flight continuity remains indisputable.
a. The five hour duration flight (2.1.1b and 2.1.2b) does not require a barogram to prove flight continuity where the flight is made under the continual surveillance of an OO.
b. In the event of failure of the pressure altitude recording in a flight recorder, evidence of flight continuity may be assessed from a time plot of GNSS calculated altitudes provided the rule on the
setting of sampling rates is followed (4.3.1).
Absolute altitude, gain of height, and start altitude must normally be verified from atmospheric pressure data recorded by a barograph. External measurement (see 4.7.1) may be used only when the required accuracy can be verified.