Usually, when making charts, they use true north up for their charts.
However, I found that there is a north arrow in jeppesen approach and sid chart.
And.. what north arrow means?
Is it indicating true north or magnetic north?
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$\begingroup$ I would be amazed if Approach charts used anything but magnetic, as thats what you're reading on your instrumwents when using them. But trying to find some actual evidence of that $\endgroup$– Jamiec ♦Feb 9, 2022 at 15:45
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$\begingroup$ Idon’t know about Jepp but just overlayed an FAA chart over the map in ForeFlight and they are definitely oriented to True North. $\endgroup$– JScarryFeb 9, 2022 at 18:23
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$\begingroup$ @JScarry the orientation may well be but the question is about the north indicator/arrow on the chart (if I understood correctly) $\endgroup$– Jamiec ♦Feb 9, 2022 at 18:31
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3 Answers
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All charts are drawn in reference to true north, and arrows or isogonic lines (depending on the type of chart) show how to convert that to magnetic.
The reason is that true north doesn’t change over time, but magnetic north does.
If charts were drawn to magnetic north, they’d have to reframe every chart every few years as the variation changed. However, by drawing them to true north, they just need to update the arrow or isogonic lines, and everything else stays the same.
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$\begingroup$ Is this documented somwhere in the JeppView software? $\endgroup$ Jul 26, 2022 at 8:37
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Jeppesen Do provide some Guidance on the use of their charts but do not explicitly state whether the "North arrow" in use is showing magnetic or true north.
However, I think we can surmise that what they depict is magnetic for two reasons
- Instrumentation in use when using these charts (Compass, DI, HSI) will all be reading magnetic so it makes most sense that bearings shown will be magnetic
- If they were depicting true, then they would also have included magnetic variance so the user can calculate magnetic. They do have this on en-route charts, but not on approach plates.
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A little late to the party:
- All charts are referenced to True North. Therefore the picture we see is True.
- On a VFR chart we measure the True Track referenced to ground landmarks, but then we convert it to Magnetic, since we are flying with reference to our magnetic compass or whatever.
- An IFR chart is still referenced to TN pictorial-wise, but all the bearings etc are Magnetic, because we are not flying using external references, and the tracks are all pre-defined and ready for us in Magnetic.
- The North arrow on the charts (ie Jepp) always points to the TN, no matter which chart you are looking at. Difference is that in En-Route / SID / Arrival charts there is no need to show the Variation (see 3 above). The only calculation needed is in case we have the wind in True (ie pre-flight wx info - Metar-Taf). But remember, the tower or the ATIS will pass to us the MAGNETIC wind and in that case, no calculation is necessary.
- The TN and MN (together with the appropriate MV) is shown only on the Terminal (airport) chart for obvious reasons (including reference for the wind calculations etc)
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$\begingroup$ Thx! Your answer really helped me. I couldn't find any explicit answer on it. $\endgroup$– moonAug 2, 2022 at 6:45