Mercator Sailing: Course and Distance
08-30-2018, 05:49 AM
Post: #12
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
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:

Code:
                                           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.

Dieter
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 Messages In This Thread Mercator Sailing: Course and Distance - Eddie W. Shore - 08-10-2018, 03:08 AM RE: Mercator Sailing: Course and Distance - PedroLeiva - 08-10-2018, 11:23 AM RE: Mercator Sailing: Course and Distance - Dieter - 08-12-2018, 05:13 PM RE: Mercator Sailing: Course and Distance - Eddie W. Shore - 09-22-2018, 11:37 PM RE: Mercator Sailing: Course and Distance - Gene222 - 08-24-2018, 07:21 PM RE: Mercator Sailing: Course and Distance - Dieter - 08-25-2018, 06:08 AM RE: Mercator Sailing: Course and Distance - Eddie W. Shore - 09-22-2018, 11:39 PM RE: Mercator Sailing: Course and Distance - Gene222 - 08-26-2018, 12:30 AM RE: Mercator Sailing: Course and Distance - Dieter - 08-26-2018, 07:18 AM RE: Mercator Sailing: Course and Distance - Albert Chan - 09-10-2022, 03:17 PM RE: Mercator Sailing: Course and Distance - Gene222 - 08-28-2018, 12:46 AM RE: Mercator Sailing: Course and Distance - Dieter - 08-28-2018, 08:53 AM RE: Mercator Sailing: Course and Distance - Dieter - 08-28-2018, 04:49 PM RE: Mercator Sailing: Course and Distance - Gene222 - 08-29-2018, 09:02 PM RE: Mercator Sailing: Course and Distance - Dieter - 08-30-2018 05:49 AM RE: Mercator Sailing: Course and Distance - Gene222 - 08-30-2018, 11:59 PM RE: Mercator Sailing: Course and Distance - Gene222 - 08-31-2018, 02:15 AM RE: Mercator Sailing: Course and Distance - Dieter - 08-31-2018, 05:46 AM RE: Mercator Sailing: Course and Distance - Dieter - 09-01-2018, 05:51 AM RE: Mercator Sailing: Course and Distance - VadimV - 12-21-2022, 08:31 PM RE: Mercator Sailing: Course and Distance - Gene222 - 09-01-2018, 02:52 AM RE: Mercator Sailing: Course and Distance - Gene222 - 09-02-2018, 04:03 PM RE: Mercator Sailing: Course and Distance - Dieter - 09-02-2018, 06:27 PM RE: Mercator Sailing: Course and Distance - Gene222 - 09-03-2018, 10:10 PM RE: Mercator Sailing: Course and Distance - Dieter - 09-04-2018, 07:19 PM RE: Mercator Sailing: Course and Distance - Gene222 - 09-05-2018, 05:46 PM

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