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This is the place to discuss general issues related to the U-boat war or the war at sea in WWII. 
Re: Accuracy of Coordinates
Posted by: Urs Heßling ()
Date: October 11, 2020 12:01PM

Ken Dunn Wrote:
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> First as Mark points out, they were primarily > determined by celestial navigation at some point. However, celestial navigation wasn’t as simple as looking at a GPS device and writing down the numbers. It was a rather complicated procedure that involved taking sightings with a sextant then based on the time of day where you were, the angles involved, at least one set of tables, and some math (and perhaps other things I am not aware of) you could come up with a latitude & longitude. However if it was a star sighting you had better be using the right star….

The correct procedure was to have at least two men take the sightings at the same time and compare notes before proceeding but frequently that wasn’t possible under wartime conditions. Getting this right on the rocking and rolling open bridge on a U-boat at sea wasn’t all that simple nor was it that simple on the bridge of a ship. The weather had something to do with it too.
> However, this was the best technology had to offer at the time.

Hi,

there`s still more to be said ...

For obtaining a position in astronomical navigation with a sextant, you need a recognizable horizon. By obtaining the vertical angle between horizon and the celestial objects (sun, moon or star) you get the numerical data to find your position. The best time for that is dawn and dusk.
BUT the submarines normally didn`t have the opportunity to surface at that time. For obtaining a position at night - when surfacing was less dangerous, at least before the introduction of radar in aircraft - you did need an "artificial horizon"
The solution was the "bubble sextant", see [hydrography.pro]

greetings, Urs

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Subject Written By Posted
Accuracy of Coordinates Sergio 10/08/2020 03:37PM
Re: Accuracy of Coordinates Michael Lowrey 10/09/2020 12:27AM
Re: Accuracy of Coordinates Mark McShane 10/09/2020 05:12AM
Re: Accuracy of Coordinates Ken Dunn 10/09/2020 06:25PM
Re: Accuracy of Coordinates Urs Heßling 10/11/2020 12:01PM
Re: Accuracy of Coordinates Ken Dunn 10/11/2020 01:00PM
Re: Accuracy of Coordinates Urs Heßling 10/11/2020 02:09PM
Re: Accuracy of Coordinates Sergio 10/12/2020 09:45AM
Re: Accuracy of Coordinates Ken Dunn 10/12/2020 12:32PM
Re: Accuracy of Coordinates Sergio 10/12/2020 01:51PM


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