How many direct magnetic courses can there be between two points? Sometimes the answer is three. How many can possibly be right? Actually, all of them.
Mag Course mismatches
I looked at the arrivals into Chicago OHare and noticed something peculiar. Both the BENKY ONE and BRADFORD FIVE arrivals have a transition route from Kirksville VOR (IRK) to LOAMY intersection. But the BENKY arrival shows a course of 068 degrees while the BRADFORD arrival shows 059. I put IRK direct to LOAMY in my GPS ... and got a third course of 064.
Key Takeaways:
- Multiple magnetic courses can exist for the exact same direct path between two points due to varying applications of magnetic variation.
- Magnetic variation values used by VORs, airports, charts, and GPS systems differ because they are updated at different times, use different epoch years, or apply varying computational models.
- Despite these differences in displayed magnetic courses, all methods ultimately describe the same accurate ground track, which is the critical element for navigational purposes.
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