SUBSIM Radio Room Forums



SUBSIM: The Web's #1 resource for all submarine & naval simulations since 1997

Go Back   SUBSIM Radio Room Forums > Silent Hunter 3 - 4 - 5 > Silent Hunter 5
Forget password? Reset here

Get ready for a whole new level of realism!
Reply
 
Thread Tools Display Modes
Old 06-17-21, 02:32 PM   #166
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

Quote:
Originally Posted by les green01 View Post
kinda like me trying to figure a intercept path to a convoy or task force
I think that for such cases it is worth hone your skills in mathematics in order to take navigation into your own hands at especially crucial moments, in other cases you can completely rely on your navigator. Ask questions here, or in the comments to the video if you need help.
  Reply With Quote
Old 06-17-21, 02:49 PM   #167
les green01
Seasoned Skipper
 
les green01's Avatar
 
Join Date: Jan 2002
Location: Freeman Missouri
Posts: 1,600
Downloads: 1301
Uploads: 0
Default

i try watching your video and it just way over my head you lose me basic right at the start my math level is second grade level
__________________
I'll tell you what bravery really is. Bravery is just determination to do a job that you know has to be done.
Audie Murphy
les green01 is online   Reply With Quote
Old 06-17-21, 03:07 PM   #168
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

Quote:
Originally Posted by les green01 View Post
i try watching your video and it just way over my head you lose me basic right at the start my math level is second grade level
In my videos, I proceed from the fact that listeners know what latitude and longitude are, they know that 1 degree consists of 60 arc minutes, they can add and subtract angles, they know what sine and cosine are, they can solve a right triangle. This is not to say that the mathematical component of navigation is "very simple", but it is quite "simple" that allowed the NCO to be used as a U-Boat navigator.
  Reply With Quote
Old 06-17-21, 03:23 PM   #169
CaptBongTrillion
Swabbie
 
Join Date: Jun 2014
Posts: 12
Downloads: 19
Uploads: 0
Default

Believe it or not, my new years resolution was to get better at math, and since it's now June and I got bored with math problems a few months ago, I think I will count this It definitely helps with mental math.

As is probably evident, for me personally, the calculation of GHA was the hardest part with all the hour, min and sec adjustments. And GHA seems to be a common denominator in the different methods.

I might try the 2 stars graphical map method to get both lat/lon. My understanding is that it can be done at any time regardless of whether the stars are at their upper culmination (this is good b/c I don't think I understand upper culmination yet). However, I think I might cheat and use the same GHA for both star observations and try to take the two observations as quickly as possible. This way I only have to determine one GHA instead of properly determining both GHA values. I assume error will still be quite minimal.
CaptBongTrillion is offline   Reply With Quote
Old 06-17-21, 03:49 PM   #170
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

What is good about the graphical method with Messkarte, you actually measure two stars almost simultaneously, then read from the Messkarte LHA of the second star, subtract the SHA of this star from it and add to the obtained SHA Polaris value to get the LHA Polaris and determine your latitude using the correction table to the altitude Polaris. Longitude can be determined to the nearest degree by subtracting SHA from LHA (read from Messkarte), and then subtracting GHA Aries at the time the stars were measured from the obtained value.
  Reply With Quote
Old 06-17-21, 11:24 PM   #171
les green01
Seasoned Skipper
 
les green01's Avatar
 
Join Date: Jan 2002
Location: Freeman Missouri
Posts: 1,600
Downloads: 1301
Uploads: 0
Default

so can you take a shot off of the little dripper or is just like a star or a planet
__________________
I'll tell you what bravery really is. Bravery is just determination to do a job that you know has to be done.
Audie Murphy
les green01 is online   Reply With Quote
Old 06-18-21, 01:14 AM   #172
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

Ultimately, any object can be used for celestial navigation. If it is such a distant object as a star, then it is enough to know its celestial coordinates (declination is a celestial coordinate similar to latitude, right ascension is a celestial coordinate similar to longitude). If the object is close enough to the earth (Sun, Moon), then in addition to the celestial coordinates, it is necessary to take into account the distance to these objects and their geometric dimensions.
  Reply With Quote
Old 06-20-21, 02:28 PM   #173
CaptBongTrillion
Swabbie
 
Join Date: Jun 2014
Posts: 12
Downloads: 19
Uploads: 0
Default

Just want to point out that the graphical method for lat/long requires very little special math if that's a problem for people. However, I want to make sure I'm doing it right.

My fix was 5.7 km from where the navigator said (granted, the navigator has random error, only reports to arc minute precision and my map work is probably sloppy). But something happened that seemed different from the demonstration video during my map work. My 90 degree LOP line from the Betelgeuse azimuth transfer line actually crossed the azimuth transfer line from Polaris, which doesn't happen in the demonstration video. In the video, only the LOP lines cross. Is this normal, or did I mess something up? Sorry, if I'm messing up the terminology here too.
CaptBongTrillion is offline   Reply With Quote
Old 06-20-21, 02:43 PM   #174
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

@CaptBongTrillion, Please provide the date, dead reckoning position, UT + Altitude for Betelgeuse and Polaris, so that I know the details of your task.

As for the intersection of non-LOP lines, this happens quite often and should not distract you. You should clearly see the intersection of LOP 1 and LOP 2 and you need to draw a "spherical transfer" to properly postpone the "map transfer".

Last edited by Alpheratz; 06-20-21 at 03:05 PM.
  Reply With Quote
Old 06-20-21, 03:08 PM   #175
CaptBongTrillion
Swabbie
 
Join Date: Jun 2014
Posts: 12
Downloads: 19
Uploads: 0
Default

Sure, thanks for having a look.

1939 Dec 14; 58 N 0 E; PoD=Wilhelmshaven; GHA for 8pm (22° 35.3')

Betelgeuse: 22:26:23 UT; 34° 39.7' h; azimuth transfer 144.5°, -21.3 km
Polaris: 22:25:25 UT; 59° 1.8' h; azimuth transfer 359.5°, 32.8 km

I did end up with two LOP lines crossing, but it just looked different from the video.

EDIT: I think the navigator said 58°18'N 0°7'E, so the fix was pretty close to that point.

Last edited by CaptBongTrillion; 06-20-21 at 03:53 PM. Reason: wrong PoD
CaptBongTrillion is offline   Reply With Quote
Old 06-20-21, 04:05 PM   #176
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

My drawings. "Map transfer" = 16,9 km
Observed position N 58 deg 16,3' E 0 deg 8,5'









  Reply With Quote
Old 06-20-21, 04:17 PM   #177
CaptBongTrillion
Swabbie
 
Join Date: Jun 2014
Posts: 12
Downloads: 19
Uploads: 0
Default

Wow cool! That's what I saw on my screen haha. I think that's close enough for me. No more GPS.
CaptBongTrillion is offline   Reply With Quote
Old 06-20-21, 04:24 PM   #178
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

By the way, with the new sextant, when you use UT, PoD is now irrelevant (except when you are calculating local noon or nautical twilight.
  Reply With Quote
Old 06-22-21, 12:56 PM   #179
CaptBongTrillion
Swabbie
 
Join Date: Jun 2014
Posts: 12
Downloads: 19
Uploads: 0
Default

Just wanted to share a fun fact I read related to this. The U.S. Navy did not train officers in celestial navigation for a period of about 10 years because it was assumed that GPS would always work. About 5 years ago, they realized this probably wasn't a good assumption and started training in celestial navigation again
CaptBongTrillion is offline   Reply With Quote
Old 06-22-21, 01:14 PM   #180
Alpheratz
Stowaway
 
Posts: n/a
Downloads:
Uploads:
Default

Yes, I've heard about it. Indeed, satellite navigation devices can be vulnerable to external influences: for example, electronic suppression technology, an electromagnetic pulse from a nuclear explosion, or well-known hackers who can take over your home Wi-Fi ironing device.
  Reply With Quote
Reply

Tags
celestial navigation, sextant

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 03:53 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright © 1995- 2023 Subsim®
"Subsim" is a registered trademark, all rights reserved.