Topographical Maps and Map Reading — Page 229, Lesson 209

I want to walk you through the qualities that make a good visual checkpoint, and then we'll look at the typical features you'll actually use in flight. This is the heart of practical map reading, so let's take it step by step. First, the single most important attribute: contrast. A visual checkpoint should contrast in colour or texture with its surroundings. That's the whole game — you need something that stands out from the ground around it. But here's the catch, and it's a big one: contrast is not a fixed property. It changes with the seasons and with geographic location. A feature that stands out brilliantly in summer may be nearly invisible in winter, and the same logic applies between polar regions and desert regions. The rules are entirely different depending on where and when you fly. Now, remember you may have to map-read at night. At night, the rules of contrast are significantly different. Unless there's a good level of moonlight, your checkpoints must be lit. That's a hard requirement — no moonlight, no lit features, no reliable checkpoint. And I want to flag a serious safety point here: poor visual contrast in certain meteorological or geographic conditions creates a real flight safety risk, because it can lead to visual illusions. That's not a minor annoyance; that's a hazard you have to respect. Here's the honest truth about checkpoint selection: it is rare for a visual checkpoint to have all the attributes we've discussed. Your selection for any given flight will probably be a compromise. What you choose depends heavily on three things — the altitude you intend to fly, the seasonal and meteorological conditions, and the nature of the terrain over which you'll be navigating. And I want to be clear: no guide can be comprehensive. You, the pilot, must weigh your own selections against the ideal criteria. That's a judgement call you own. Now let's look at some typical visual checkpoints, starting with coastlines. Coastlines generally provide excellent daytime visual checkpoints, and given reasonable moonlight, they can also be used at night. Here's the useful part: coastlines are rarely uniform for any great distance. That irregularity is your friend, because precise navigation can normally be achieved by reference to specific features — estuaries, headlands, ports, or lighthouses. Those are your aiming points along a coastline. Next, water features. Lakes, large rivers, and canals normally show up well, even when you account for seasonal variations like floods and droughts. That's a nice robustness — water tends to persist as a feature. And there's a practical rule to remember: water features tend to occur in the lowest ground in a particular area. So when you see water on the map, you know you're looking at the low ground, and that tells you something about the terrain you're crossing. Let me pause there, because we've just started the water features discussion and I want to make sure the foundation is solid before we go further.