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Learning hub · General Navigation · Lesson 5

Map reading, pilotage and what to do when lost

Most VFR navigation is done by looking out of the window and matching what you see to the chart. This lesson covers how to choose checkpoints you can actually find, how to keep track of where you are, and what to do when the chart and the ground stop agreeing.

About 12 minutes, plus the quiz. Part of General Navigation.

1. Pilotage: navigating by what you see

Pilotage means flying from one visible feature to the next, using a chart. It works best together with dead reckoning: the heading and time you worked out on the ground tell you where to look, and the ground tells you whether the numbers were right. Neither is enough alone. A good pilot uses the planned time to know when to expect a feature, and the feature to correct the plan.

Turn the chart so that your track points up the page, so that left on the chart is left out of the window. Fold it so that the whole leg is visible without opening it again in a busy cockpit, and keep the next few checkpoints marked.

2. Choosing checkpoints

A good checkpoint is easy to see from your height, easy to tell from its neighbours, and unlikely to change. A small farm is a poor one, a chimney next to a lake is better. Rough guidance: pick one every 10 to 15 NM, or every few minutes, and closer together in poor visibility or unfamiliar country. Mark the time you expect to pass each one.

  • Line features are long features such as a river, a railway, a motorway, a power line or a coast. They are hard to miss, but they do not tell you where along the line you are.
  • Point features are a town, a lake, an airfield or a mast. They pin down your position along the track.
  • A catch feature is a line feature that crosses your track beyond the point you are aiming for. If you reach it, you have flown too far and you know which way to turn back.
  • A collecting feature is a line feature that leads to your target, so that if you drift to one side you can pick it up and follow it in. A railway that runs into the town you are looking for is one.
  • A tracking feature runs along your track and lets you hold the line by eye. Do not fly directly over it every time: stay a little to one side where you can see it.

Prefer a combination. A point feature to confirm your position, a line feature behind it to catch you if you miss it. Before take-off ask of each leg: what will tell me I have gone too far, and what will tell me I have drifted to one side?

3. Chart symbols that matter

Read the legend of the chart you are using, because symbols differ between charts and countries. Check that the chart is current. Some items you should always look for:

  • Obstacles such as masts and wind turbines. Heights are usually printed as an elevation above mean sea level, with the height above the ground in brackets. Compare the elevation with your altitude, not the height in brackets.
  • Airspace boundaries, with their class, lower and upper limits and frequencies. Check them against your route before you fly, not once you are close.
  • Prohibited, restricted and danger areas, and military low-flying areas.
  • Spot heights and contours, which tell you where the highest ground is.

The chart is only as good as its date. New masts, wind farms and roads appear between editions. Use it together with a current briefing.

4. Thumb and time

Keep your thumb on the chart at your last confirmed position, and move it to each checkpoint as you pass it. You always know where you were last. Then compare the clock with the plan: if the next checkpoint was due in 8 minutes and 6 have gone, start looking. If it was due 3 minutes ago and you have not seen it, do not guess; start the steps in section 7.

Fix as often as you can. Each time you identify a feature, you have a new positive fix, and the circle of doubt shrinks to nothing again.

5. How big is the doubt?

After your last fix you have a dead-reckoning position: the last fix plus the distance flown along the track. The true position is somewhere around it. Two things make that circle grow:

  • Track error. Use the one-in-sixty rule from the previous lessons: one degree off is one mile off for every 60 NM flown.
  • Wind you did not expect. A wind that is 10 kt different from the forecast moves you 10 NM in an hour, or 5 NM in half an hour.
radius ≈ distance × error° ÷ 60 + wind error × time

This model adds the two, so it is on the generous side. The point is that the circle gets bigger with every minute that goes by without a fix.

Try it: change the time since the last fix, the groundspeed, the track error and the wind you did not expect. The white dot is the dead-reckoning position, the amber circle is the doubt, and the features on the chart turn amber when they lie inside it. Those are the features worth looking for. The numbers on the chart are invented.

This diagram needs JavaScript to move. The explanation above and the exercises below cover the same ideas.

6. A worked example

Your last positive fix was a railway bridge 20 minutes ago. Groundspeed is about 90 kt. You think you may have held the heading to within 3°, and the wind could be 10 kt different from the forecast. All the numbers are invented.

  1. Distance flown: 90 × 20 ÷ 60 = 30 NM.
  2. Track error: 30 × 3 ÷ 60 = 1.5 NM.
  3. Wind error: 10 × 20 ÷ 60 = 3.3 NM.
  4. Circle: about 5 NM in radius. That is roughly 80 square miles. With 10 NM visibility you can see across it, so a feature that matches the chart inside the circle is a good candidate for your new fix.

Left alone for another 20 minutes, the circle roughly doubles. That is why you act early.

7. When you are not sure where you are

It happens to everyone sooner or later. The most important thing is to decide early, while you still have fuel and daylight, and not to hope. Work through it in this order.

  1. Fly the aeroplane. Keep the wings level, hold the altitude and, for now, the heading. Do not make big turns to look for something. Note the time.
  2. Think, then look. What was the last positive fix, when was it, and what heading and groundspeed have you held since? Work out the circle as in the example. Look for large features, such as a river, a railway or a coast, and match them to the chart. Be willing to ask whether what you see really matches, or only looks a bit like it.
  3. Use what you have. Check the GNSS or the VOR if the aeroplane has them, and the app on your tablet. These are aids, not a reason to stop looking out. Do not fly towards a position you have only a guess for.
  4. Climb if you can do it safely. A greater height gives a wider view and a better radio range. Stay clear of cloud and controlled airspace you have no clearance for, and keep to the terrain and the fuel you have.
  5. Talk to someone. Call the air traffic service or the information service you were last speaking to, or the emergency frequency 121.500 MHz. Say the callsign, that you are uncertain of your position, your last known position, the time, your heading, altitude and the fuel you have. They may ask you to select a transponder code, and they may be able to give you a position or a heading to steer.
  6. Say how serious it is. A call that begins PAN PAN, PAN PAN, PAN PAN tells everyone you have an urgent problem. MAYDAY is for grave and imminent danger, such as running out of fuel with no airfield in reach. The transponder code 7700 means an emergency: use it when you have declared one, or when ATC tells you to. Being unsure of your position is not by itself a reason to select 7700, but do not wait until it is too late to ask for help.

If you are in the circle and you still have time and fuel, a sensible plan is to fly to the nearest long line feature, such as a coast or a motorway, so that you know the direction to follow it, or to fly to a known large landmark. If daylight or fuel is running out, land at a suitable field or airfield you can identify rather than fly on. Ask for help early, because help costs nothing and being lost costs a lot.

GNSS and tablets fail, and so do batteries. Keep the paper chart folded to the leg, keep marking your fixes, and never depend on a single source. This is a training lesson and is not certified for navigation.

8. Try it yourself

Work each one out on paper first, then open the answer to compare. The numbers are invented.

  1. Your last fix was 25 minutes ago. Groundspeed has been about 100 kt, you allow a track error of 4° and the wind may differ from the forecast by 5 kt. How big is the circle?
    Show the answer

    Distance flown: 100 × 25 ÷ 60 ≈ 42 NM. Track error: 42 × 4 ÷ 60 ≈ 2.8 NM. Wind error: 5 × 25 ÷ 60 ≈ 2.1 NM.

    Added together, the radius is about 5 NM. With reasonable visibility, look for the chart features within 5 NM of the dead-reckoning point.

  2. Your destination is a small airfield next to a lake, in flat country. You can use a long railway that crosses your track 6 NM beyond the airfield, or a long road that runs alongside your track 10 NM to the south. Which is the catch feature, and what does the other do?
    Show the answer

    The railway that crosses your track beyond the airfield is the catch feature. If you reach it, you have flown past the airfield and you know to turn back.

    The road alongside your track is a tracking feature. It helps you hold the line, but it will not tell you that you have gone too far.

  3. The next checkpoint is 18 NM away at a groundspeed of 90 kt. After 15 minutes you have not seen it. What do you do?
    Show the answer

    18 NM at 90 kt takes 18 ÷ 90 × 60 = 12 minutes. You are 3 minutes late, and in that time you have flown about 4.5 NM further than planned.

    You are not necessarily lost, but you are no longer sure of your position. Hold the heading, note the time, work out a circle and look for the catch feature beyond the checkpoint and for any large feature on the chart. Do not turn round on a hunch. If you cannot find a fix soon, start asking for help.

9. Check yourself

Five original practice questions. Answer them, press Check answers and read each explanation.

1. Which of these makes the best catch feature?

A catch feature crosses your track beyond the target, so you cannot pass it without noticing. A road alongside your track is a tracking feature, a farm is easy to miss and a cloud shadow moves.

2. You realise you are unsure of your position. What comes first?

Flying the aeroplane always comes first. Holding the heading and altitude keeps the circle of doubt as small as it can be, and noting the time gives you a number to work with. A sudden turn or a descent makes things worse.

3. You have flown 60 NM with a track error of 4°. About how far are you off track?

One-in-sixty: one degree is one mile for every 60 NM flown, so 4° over 60 NM is about 4 NM.

4. When is it right to select 7700 on the transponder?

7700 tells every controller you have an emergency. If you are only unsure of your position, call ATC and say so, with a PAN PAN call if you need urgent help. Use 7700 when you declare an emergency or when you are told to.

5. What happens to the circle of uncertainty as time passes without a new fix?

Track error grows with distance and wind error grows with time, so the circle grows with every minute. That is why you fix often, and why you act early when you are unsure.

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For training and situational awareness only. Not certified for navigation. Always use official charts, the AIP, NOTAMs and a proper weather briefing for real flights.