Let me set the scene — Page 449, Lesson 426

I want to walk you through what's on this page, because it's a classic piece of General Navigation that trips up a lot of students. What you're looking at here is a grid of numbers — and those numbers are magnetic variation values, in degrees, plotted across a chart of the North Atlantic. Let me set the scene. This is a chart that covers a big chunk of the northern hemisphere — you can see latitude lines running from about N 50 down through N 20, N 10, the Equator (0), then S 10, S 30, S 52, S 60. And the longitude values run from about 56°W across to 9°E — so we're looking at the Atlantic, from the eastern seaboard of North America over to western Europe and Africa. Now, the key idea: magnetic variation is the angular difference between True North and Magnetic North at any given point on the Earth's surface. It's not constant — it changes from place to place, and it changes over time. So what this chart gives you is a grid of variation values, each one measured at a specific latitude and longitude intersection. Each number you see — like 22, 21, 20, 19, 18, 17, 16 — is the variation in degrees at that point. Let me read a few of these for you so you can see the pattern. Up at the top, around N 50 and 56°W, you've got values like 22 and 23 degrees. As you move eastward along that same latitude, the numbers step down — 21, 20, 19, 18 — until you get to around 9°E where you're down to about 16 degrees. So the variation is decreasing as you go east. Now here's the critical part — the sign of the variation. Look at the far left column, around N 50 and 56°W: the values are 22, 23, 22, 21, 19, 17, 14, 12, 9. Those are all positive — meaning easterly variation, where Magnetic North lies to the east of True North. But watch what happens as you move south. Around N 20 and 56°W you're at about 20 degrees. By the time you get to the Equator you're around 22 degrees. But then, as you cross into the southern hemisphere, the numbers start to decrease — S 10 shows about 18, S 30 about 17, S 52 about 16, and down at S 60 you're at about 16 degrees again. And here's the subtlety — the variation is still easterly (positive) across this whole chart, but the magnitude changes with latitude. Notice how the values decrease as you go south from the Equator — that's the variation getting smaller in magnitude, not changing sign. The chart is telling you that in this region, the variation is always easterly, but it's strongest around the Equator and weaker toward the poles. Now, why does this matter for you as a pilot? Because when you're navigating, you need to convert between True and Magnetic headings. The rule is simple: Variation East, Magnetic Least — if the variation is easterly, the magnetic value is smaller than the true value. So if you're flying at N 50, 56°W with a variation of 22°E, and your true track is, say, 090°, your magnetic track would be 090° minus 22° = 068°. That's the practical application of every single number on this grid. Let me also point out the structure of the chart itself. Notice how the numbers are arranged in rows and columns — each row is a line of latitude, each column a line of longitude. The values are given at regular intervals — you can see the latitude lines stepping down by 10 degrees (N 50, N 40, N 30, N 20, N 10, 0, S 10, S 30, S 52, S 60), and the longitude lines stepping across by 5 degrees or so (56, 54, 52, 50, 48, 44, 40, 37, 34, 29, 25, 21, 17, 14, 12, 9). So if you're at a point between these grid intersections, you'd interpolate — estimate the variation between the two nearest values. One more thing to notice — the symmetry of the values. Look at the row around N 50: it reads 22, 23, 22, 21, 19, 17, 14, 12, 9 — it rises slightly then falls. And the row at S 52: 16, 16, 16, 16, 16, 16, 16, 16, 16 — nearly constant. That tells you the variation field is not uniform — it has a gradient that changes with both latitude and longitude. So, to sum up what this page is: it's a variation chart — a grid of magnetic variation values in degrees, covering the North Atlantic from about 56°W to 9°E and from N 50 to S 60. The values are all easterly (positive), ranging from about 9 to 23 degrees, and they vary with position. When you navigate, you take the variation at your position from this grid, apply it to convert True to Magnetic (or vice versa), and remember: Variation East, Magnetic Least. That's the whole story of this page.