Version 1. - May 2006
Navigation in practice
In flight most balloon pilots navigate accurately enough using approximate ‘rule of thumb’ measurements and calculations. For example, you fix your position on the map at take-off and again after ten minutes, hold your thumb and forefinger against the two fixes on the map, and then hold them against the scale at the edge of the map, or against the grid, to check the distance. Multiply this by 6 to get the distance you are likely to cover in an hour, or simply count off multiples of the same distance ahead with thumb and forefinger to plot your estimated position after 20 or 30 minutes.
In flight navigation checklist: Topographic map, compass and clock are mandatory Aviation chart need not be carried provided the essential information from the chart has been marked on your topographic map Pencil and eraser are useful to fix your position on the map Binoculars, GPS and spare GPS batteries also useful.
Units of measurement
Horizontal distance for navigation purposes is in nautical miles (NM). 1 NM = 6080ft or 1852m, about 12% longer than a statute mile. 'Miles' in aviation always means nautical miles, unless stated otherwise.
Horizontal speed is in knots (KT). 1 knot = 1 nautical mile per hour. There is no such thing as a knot per hour! Watch out - wind speed is usually given in knots, but sometimes in km per hour.
Horizontal distance for other purposes (eg, for visibility or clearance from cloud) is in kilometres (km) or metres (m).
Direction is shown in degrees, always as a 3 figure group. East is 090 , North is 360 . Direction is usually measured towards the object or direction of flight. However, wind direction is always expressed as where the wind is coming from. 12 knots of wind from the south (180 ) is abbreviated in forecasts as 180/12 or 18012.
Height or altitude (vertical distances) in aviation are always in feet. Altitude is the vertical distance of a level, a point, or an object considered as a point, measured from mean sea level, eg 2,000ft AMSL (above mean sea level). Height is the vertical distance of a level, a point, or an object considered as a point measured from a specified datum such as ground level, eg 1200ft AGL (above ground level)
It is a common mistake to omit the datum. Note: a maximum allowed (or practical) altitude is called a ceiling.
© Australian Ballooning Federation Inc
ABF Pilot Training Manual Part 8