Charts and Position Fixing
Reading the chart at night
The 1:500,000 chart is the normal planning chart. Know the symbols for controlled airspace, prohibited and restricted areas, spot heights, obstacles, radio navigation aids and airfield data. At night the minimum safe altitude must clear terrain plus obstacles plus a margin; unlit masts and hills are easy to miss visually, so the chart is the primary terrain warning. Study the route before flight and mark every obstacle within 5 nm of track.
Position fixing methods
A fix can be a VOR radial crossed with DME, two radials, a bearing and distance, a GNSS position, or a visual fix from a lit town or airfield. Plot each fix with a time mark so track and groundspeed can be calculated. A single line of position is not a fix - it only tells you that you are somewhere on that line. Use at least two independent sources where possible.
Worked example
You are on VOR radial 090 at 25 DME. The chart shows a town 12 nm east of the beacon on the same radial. Reasoning: the DME gives distance from the beacon and the radial gives the line; the town confirms the fix. That is a valid two-parameter fix. If only the radial were available, you would know the line but not the position along it.
Traps
Treating one radial as a fix; using a magnetic bearing without variation; plotting with a thick pen; forgetting whether a chart spot height is in metres or feet; and assuming a lit area is the expected town.