Topographical Chart — Page 132, Lesson 131

I want to walk you through the topographical chart that we use for VFR cross-country flight planning. This is a new topic, so let’s start from the very beginning. The reference chart for Part-FCL 033 01 00 00, which covers flight plans for cross-country VFR flights, is the Jeppesen VFR + GPS Chart GERMANY ED - 6 EDITION 1999. That’s a specific chart, but the principles apply generally. This chart uses a Lambert Conformal Conic Projection. That’s a type of map projection where the parallels of latitude are arcs of circles and the meridians are straight lines converging toward the poles. The standard parallels for this chart are N37° and N65°. The scale is 1/500,000, meaning one unit on the chart represents 500,000 of the same units on the ground. Elevations on the chart are given in feet. The chart is designed for flight in Visual Meteorological Conditions, or VMC, in accordance with Visual Flight Rules, VFR. It is effective only below certain altitudes depending on which country you’re flying over: below FL125 in Austria, below FL115 in France, below FL100 in Germany, and below FL150 in Switzerland. So if you’re planning a VFR flight in Germany, you must stay below Flight Level 100 when using this chart. The isogonic lines — those are lines of equal magnetic variation — are valid for the year 1999. You can find them at the top of the chart at E008° 55’ and E012° 15’. The highest spot elevation on this chart is 12,028 feet, located at coordinates N47°07.4 E012°20.8. And if you need to know which adjacent charts cover the surrounding area, there’s a diagram in the top left-hand corner of the chart that identifies them. Now, let’s talk about coordinates. The chart uses the World Geodetic System of 1984, abbreviated as WGS84. This is the standard coordinate system used in aviation. The coordinates of VFR reporting points, aerodromes, and radio navigation aids are all given in WGS84. For example, the Stuttgart NDB — that’s a non-directional beacon — has coordinates N48°42.7 E009°20.1. You’ll find these coordinates in the right-hand panels of the chart. The excerpt gives you an example with three questions. I won’t read them out as a batch, but they ask you to find the WGS84 coordinates of a VFR reporting point called FOXTROTT 2 in the München Control Zone, the coordinates and ICAO designator for Innsbruck International aerodrome, and the radio navigation aid, its frequency, call sign, coordinates, and magnetic variation for MOOSBURG. The answers are on page 141. Next, let’s look at how we measure direction and distance on this chart. For true direction, you place the centre of a protractor over the midpoint of the track you want to measure. Then you align the protractor’s north-south axis parallel to the nearest meridian — that’s the line of longitude — and read off the track direction in degrees true, written as °(T). If you need magnetic direction instead, you find the mean magnetic variation for the track by interpolating between the appropriate isogonic lines. You also update that variation for the mean annual change, because magnetic variation shifts over time. Then you apply that variation to the true track direction using this rule: variation west is magnetic best, and variation east is magnetic least. What that means is: if the variation is west, you add it to the true track to get the magnetic track — that’s “magnetic best” because the number gets larger. If the variation is east, you subtract it — “magnetic least” because the number gets smaller. For distance, you measure in nautical miles. You can use either the nearest meridian scale — that’s the scale printed along a meridian line — or the nautical mile scale at the bottom of the chart. That bottom scale also includes a kilometre and statute mile conversion. The conversion factor is: 60 nautical miles equals 111.1 kilometres. That’s because one nautical mile is 1.852 kilometres, so 60 times 1.852 gives you 111.1. Let me show you the chart itself so you can see the layout and the scales. That’s the bottom of the chart with the scales and the isogonic information. Now let’s look at how pressure differences affect height measurement. This figure shows what happens when the QNH is lower than 1013.25 hPa — you get less height gained. And here’s the opposite case. When the QNH is higher than 1013.25 hPa, you get more height gained, and the temperature difference from ISA at the cruising pressure level also matters. That covers the key elements of the topographical chart: the projection, scale, effective altitudes, isogonic lines, WGS84 coordinates, how to measure true and magnetic direction, and how to measure distance with the conversion factor.