Navigation
Position and direction
Navigation questions mix geometry, magnetism and radio aids. Learn the triangle of velocities: true heading, true airspeed, wind direction and speed, and the resulting true track and groundspeed. Convert true to magnetic with variation (east is least, west is best - subtract easterly variation), then magnetic to compass with deviation. Know the isogonal and the agonic line. Map projections: Mercator gives a constant rhumb-line track with scale distortion away from the equator; Lambert conformal conic shows great circles approximately straight; polar stereographic suits high latitudes.
Radio navigation
VOR gives a radial from the station; DME gives slant range; NDB gives relative bearing and suffers night effect, coastal refraction and thunderstorm interference. ILS has a localizer, glideslope, markers and a decision altitude or height. GNSS and RNAV bring waypoints, RNP, RAIM and integrity monitoring. Be clear on the difference between a radial and a bearing, and between track and heading.
Traps
Watch 'from' versus 'to' on the OBI, magnetic versus true, and track versus heading. The 1-in-60 rule solves most drift questions quickly.
Worked example
After 60 nm you are 6 nm off track, so track error is 6 degrees. If the next waypoint is 60 nm ahead, the closing angle is another 6 degrees and the total correction is 12 degrees. If only 30 nm remained, the correction would be 12 degrees for the closing angle alone.