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Mercator Sailing: Course and Distance
08-30-2018, 05:49 AM
Post: #12
RE: Mercator Sailing: Course and Distance
(08-29-2018 09:02 PM)Gene222 Wrote:  Okay. You convinced me. I will use your ATANH formula (the first one). The formula really does need to be accurate to transition to the formula for the East-West course.

It is. For lat1 = lat 2 use the formula from post #5:

                                           1 – e²·sin²(lat)
distance = 60·|long2 – long1| · cos(lat) · ----------------
                                                1 – e²

Check it yourself: calculate the distance for two almost identical latitudes (say, 40 and 40,00001 degrees) and compare the result with the above formula.

(08-29-2018 09:02 PM)Gene222 Wrote:  I think I got the program just about done, but I need to recheck it to see if I got the signage right for all cases. I got hung up on the 0 and 180 degree meridian crossings.

Make sure the absolute value of long2 – long1 does not exceed 180°. For example, 250° East is equivalent to 110° West. Continue with this longitude difference.

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RE: Mercator Sailing: Course and Distance - Dieter - 08-30-2018 05:49 AM

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