Chart reading: relief, symbols and airspace

Navigation · Chapter 9 · DGCA CPL and ATPL

How a flat chart shows hills, what the numbers and colours mean, how to pick checkpoints and find yourself again, and the symbols for navaids and airspace.

Remember

Contours join equal heights above MSL; close together = steep.
MEF = higher of hill + 300 or mast, rounded up, in hundreds; it is not a safe altitude.
Good checkpoints are large, unique, high and contrasting, every 5-10 min; lines give track and GS checks.
Poor contrast hides the hill in front of the hill: less clearance than planned.
Lost: check, climb, DR circle of 10 %, head for a line feature, 121.5.
FIR boundary: heavy line with ticks. A level on an airway is its MEA.

What does a piece of real country look like on a chart?

The real world as a chart

What you see from the air • Hills, a river and a lake, a town, a motorway and a railway, a wood, an airfield, a radio mast • 40 km across: about 10 minutes of flying
Look straight down • A chart is the ground seen from directly above • From up here the hills are hard to see: height needs its own symbols
Flatten it into a chart • Heights become contour lines and layer colours (higher = browner) • The town turns yellow, roads red, the airfield magenta, water blue
Heights are written in • The top of the hill becomes a spot height (4 200 ft) • The mast becomes a symbol with its height (1 510 ft above the sea)
Back to the world • Every symbol stands for something real • Map-reading is turning the symbols back into this picture in your head

How does a flat chart show a hill?

From a hill to a chart

Why a paper chart still matters • Navigation sets can fail, and many light aircraft have few • Map, compass, stopwatch and eyes always work • A chart shows three things: relief, other features, and scale
Slice the hill • Cut it with flat sheets every 500 ft above mean sea level
Mark the cuts • Each cut leaves a ring round the hill at one height • That ring is a contour
Squash it flat • Press the hill onto paper: the rings stay • Close rings: steep. Far apart: gentle
Colour the layers • Fill each band with its own colour: layer tints • Darker brown = higher