4.4 Calculations and Calibrations

Time, geographical position, altitude, and means of propulsion are flight performance data which must be either recorded or measured for some or all types of flights. Using this data, calculations of distance, speed, duration, gain of height, altitude difference, height penalties and start height may be done.

4.4.1 Calculations for distance and speed

For world records, distances between two points in excess of 1000 kilometres, and in any case of dispute over a distance, the distance flown is deemed to be the length of the geodesic line joining the start point and the finish point or, if there are turn points, the sum of the geodesic lines for each leg of the course, corrected as in 1.2.11. See Annex C, Appendices 2 and 3.

a. EARTH MODEL TO BE USED

For the purpose of the calculation of FAI geodesic distances, the WGS 84 earth model shall be used. See also Annex C, Appendix 2.

When calculation of the exact distance is not critical, less accurate methods may be used. See Annex C , para 1.6b.

b. GEOGRAPHICAL COORDINATES OF WAY POINTS

NACs are to specify procedures for recording the geographical coordinates of way points from maps of their national territory using geographical co-ordinates such as Latitude and Longitude, map grid, or national grid (if such a grid exists for the area
concerned).

c. MAP SCALES

Measurement of coordinates of way points should be from a map with a scale at least as detailed as 1:250,000, and preferably 1:50,000 (if such a map exists which includes the way point concerned). For
records, if a scale less detailed than 1:50,000 was used, the NAC should be able to show that co-ordinates were taken from the most accurate map available for the way point concerned.

4.4.2 Loss of height and application of the height penalty

a. For distance flights of more than 100 kilometres, where the loss of height (1.2.7) exceeds 1000 metres, a height penalty (1.2.12) must be subtracted from the length of the course to give the official distance.

b. For distance flights of 100 kilometres or less, a loss of height exceeding 1% of the length of the course will invalidate the soaring performance.

c. For speed and duration flights, a loss of height exceeding 1000 metres will invalidate the soaring performance.

4.4.3 Flight data requirements

The minimum flight data required for each type of soaring performance is given in Table 2.

Table 2 Minimum data requirements

4.4.4 Accuracy of measurement

The minimum accuracy of measurement and calculation required for each type of flight data is given in Table 3. Any inaccuracy in ameasurement or calculation is to be interpreted to the maximum
disadvantage of the pilot.

Table 3 Minimum accuracy requirements

Precision of measurement
Care should be taken to correctly assess the precision of measurement devices so that an invalid level of accuracy is not introduced into calculations. See
Annex C for more information.

4.4.5 Combinations of measurement methods

Any combination of the measuring methods is acceptable for the various types of flights, provided the minimum requirements for accuracy of equipment in paragraphs 4.4.3 and 4.4.4 are fulfilled.

Each method used must comply with this Code as if it were the only means of proof employed.

4.4.6 Timing device calibration

When used, clocks and other time recording equipment shall be checked against official time signals both immediately before and again after the flight, covering a period of at least three hours. Any error found shall be taken into account and rounded up in the calculations. The GNSS time recording from a flight recorder may be used as an official time signal.

4.4.7 Barograph calibration
period

Barograph calibrations are required to ensure that the measurement of barometric pressure and time are checked against, and corrected as necessary, to official standards. For altitude and gain of height
records, both (a) AND (b) calibrations below are required, and the least favourable calibration of the two shall be used making the calculations for the record. For badges, start height verification,
and altitude difference calculation, either (a) OR (b) are required.

a. PRIOR TO THE FLIGHT

The calibration used must have been performed within 12 months prior to the flight or, for IGC-approved electronic barographs and FRs, 24
months.

b. AFTER THE FLIGHT

The calibration used must have been performed within one month after the flight or, for IGC-approved electronic barographs and FRs, two months.

4.4.8 Calibration correction

When absolute altitude (not altitude difference) is to be determined, the altitudes reached during a flight from the barograph evidence must be corrected for a height error arising from the actual atmospheric pressure of the day compared to the standard atmosphere.

The method of arriving at a corrected altitude is given in Annex C.