Topographical Maps and Map Reading — Page 233, Lesson 215

I want to walk you through a critical safety topic in visual navigation: the illusions and traps that can fool even an experienced pilot when reading the terrain below. Let's start with a dangerous situation called 'the hill in front of the hill'. Imagine you're flying toward a ridge or a hill, but there's another, lower hill in front of it that you can't see clearly. You plan your clearance based on what you think is the main terrain ahead, but that hidden lower hill is actually much closer and higher than you expect. Your actual clearance may be considerably less than planned. This is particularly dangerous when flying at lower altitudes, because you don't get the warning until you're right on top of it. Now, let's talk about judging height over different surfaces. Flying over a smooth water surface, snow, or a smooth desert surface makes it extremely difficult to judge height. Why? Because your eyes need texture and features to gauge distance and altitude. In an overland situation, the difficulty can be exacerbated if there are no features with vertical extent — for example, no trees. In a desert or tundra landscape, it's easy to see bushes and scrub trees and imagine they are full-size trees when they may actually be only a few metres high. That misjudgement can lead you to fly lower than you think. Now consider night flying. When you're flying over dark areas of sea or land where there are scattered pinpoints of light — from ships, oil rigs, small settlements, or isolated buildings — it is possible to become disorientated. You can confuse the scattered lights below with the scattered stars above. This situation may be exacerbated after or during aircraft manoeuvres, when your spatial orientation is already challenged. Let's move to Navigation Techniques. The book tells me that pilot navigation techniques and chart preparation requirements appropriate to visual navigation — including the 1:60 rule — are discussed in relevant flight exercise briefings. That's a separate topic we'll cover when we get there, but for now, know that the 1:60 rule is a standard tool for correcting off-track errors. The key principle here is: a disciplined approach is always the most successful. Let me walk you through the checklist that should be automatic at every phase: When setting heading from a start point or when altering heading at a turning point, always check that you are flying the correct heading and that the compass is synchronized. Always check that you have the appropriate altimeter setting and are flying at a safe altitude. Always check that you have started or restarted your stopwatch, or you know how much you are running early or late on planned time. Finally, the most important piece of advice: even the best navigators become occasionally uncertain of position. It is very tempting in this situation to carry on regardless. DON'T! Start immediately — meaning, begin your position-fixing procedure right away. Don't wait, don't hope it'll sort itself out. That hesitation is what turns a minor uncertainty into a major navigation error.