Real WWII Nav Accuracy

[Pisces]

It's time for Don1reed to show up again. He usually does when this subject rears its head.

For the time being, ... and for what it's worth, as I never used a real sextant:

I think that 5 to 15 miles would be the deadreckoning accuracy after long periods without star fixes. Not the sextant/celestial navigation accuracy. That would depend in a large part on the measurement resolution of the sextant. As 1 arcminute is about 1 nautical mile on the surface it depends on how fine the readout is. Ofcourse it also depends on how steady the sextant is held by the navigator.

[6SJ7GT]

Interesting thread,

from my reading, 1.5 miles is the practical accuracy from a moving platform. A good sextant is capable of 1/10 arcminute of accuracy, and as the design hasn't changed much for a long time (it has been that way since the 18th century). Here is site on the history of the sextant.

here's a couple of screenshots using celnav in the game map.

This uses the method of transferring the boat's position to Stellarium.

the last sight on Dubhe, I used the USNO almanac so I only had to calculate the diff of Hc & Ho. Use a convenient close intersection for the AP (32N 139 30'E):
at 03:04:30Z
Hc 17 48.9' Zn 26.7 deg both from the USNO Almanac.
Ho 17 33.6
Dist +15.3

I used the compass to find the 15.3 mi offset, then just had to use the protractor (with the tool helper to get the proper Zn) to draw the sight line and perpendicular. Here is the fix.



And the boat revealed. It was approximately 1000m from the fix but has travelled some.


I hope you get this working as using a sextant in game would enhance the immersion.
Mike

[6SJ7GT]

ps

date on the above is 8 May 1942.

Mike