[TEC] Real navigation Tutorials

[Sjizzle]

[QUOTE]

Originally Posted by palmic

Great video about langitude - it should be in the first post as more info!

Q1: How do we know on which hemisphere we are?

55.37 N is North hemisphere cos after the 55.33 is N if was S u where in the south hemisphere also if u are above equator u are in the north hemisphere if u are below equator u are in the South hemisphere

Q2: Where did you get that 20 LHA for longitude??

that come automatic from that spreadsheet file it's calculate it alone.... u need to use that file or a Almanac to find the declination, index error, LHA, without a almanac the calculation is incorrect

I just dont get it, there's no explanation, just open excel, there is 20 LHA.. i mean what?
It seems to me like i have to watch sun vertical angle periodically and when i find its on zenit, get the time..
Then somehow calculate longitude by substituing difference of sun zenit time from GMT noon and dividing somehow, but its not described here..

I dont want to use some scripted xls, i want to know how can i get LHA.

go here for online almanac to calculate your position.....
local noon is described in post #1.

PS. u can use also Stellarium a great software

Awesome work people, trying to make this work on my side to join the party

[palmic]

Originally Posted by Sjizzle

[B][COLOR=Red]55.37 N is North hemisphere cos after the 55.33 is

55.37 N is the result of latitude calculation.
You need to know which hemispehere you are on before this calculation (to decide if you will be adding, or subtracting and how )
How do you now initially you haven't cross equator if you are completely lost?

Originally Posted by Sjizzle

that come automatic from that spreadsheet file it's calculate it alone.... u need to use that file or a Almanac to find the declination

Sorry but if i would have to use some excel, i would rather turn my realism to show my position itself, i would like to use only almanac or whatever else what was available at 1939 u-boat
How to get LHA from Almanac? I want to find even longitude for myself, that Excel needs to calculate it somehow, but i haven't found how

Maybe i can ask even another way:
1) Are we able to get longitude in another time, than when the sun is at highest position? (I expect no)
2) Can i get longitude by knowledge which GMT time is the sun at highest position? I expect so, because it should be something like +15 degrees E for every hour after 12:00AM or +15 degrees W for every hours before 12:00AM minus GHA

Thank you for quick response!

[Sjizzle]

Originally Posted by palmic

55.37 N is the result of latitude calculation.
You need to know which hemispehere you are on before this calculation (to decide if you will be adding, or subtracting and how )

How do you now initially you haven't cross equator if you are completely lost?

that come automatic from that spreadsheet file it's calculate it alone.... u need to use that file or a Almanac to find the declination, index error, LHA, without a almanac the calculation is incorrect



Sorry but if i would have to use some excel, i would rather turn my realism to show my position itself, i would like to use only almanac or whatever else what was available at 1939 u-boat
How to get LHA from Almanac? I want to find even longitude for myself, that Excel needs to calculate it somehow, but i haven't found how

Thank you for quick response!

before u calculate your celestial fix u always have a dead recognition fix and u know which hemisphere are u ..... so u are not complete lost at all
u know where u was last time before the celestial fix ... u always need to make a dead recognition fix ....so not complete lost ...... and also a tip most of the german uboat mission was in the north hemisphere ......

Local Hour Angle (LHA). In astro navigation, we need to know the position of a celestial body relative to our own position.
LHA is the angle BNU on the Earth’s surface which corresponds to the angle ZPX in the Celestial sphere. In other words, it is the angle between the meridian of the observer and the meridian of the geographical position of the celestial body (GP).
Due to the Earth’s rotation, the Sun moves through 15o of longitude in 1 hour and it moves through 15 minutes of arc in 1 minute of time. So the angle ZPX can be measured in terms of time and for this reason, it is know as the Local Hour Angle.
LHA is measured westwards from the observer’s meridian and can be expressed in terms of either angular distance or time. For example, at noon (GMT) the Sun’s GP will be on the Greenwich Meridian (0o). If the time at an observer’s position is 2 hours and 3 minutes after noon, then the angular distance between the observer’s meridian of longitude and the Greenwich Meridian must be (2 x15o ) + (3x 15’) = 30o 45’. Because it is after noon at the observer’s position, the longitude of that position must be to the East of the Greenwich Meridian since the Earth rotates from West to East. Therefore the observer’s longitude must be 30o 45’ East and since LHA is measured westwards from the observer’s meridian, the LHA must also be 30o 45’. However, it should be noted that as the Earth continues to rotate eastwards, the GP of the Sun will continue to move westwards so the LHA at the observer’s position will be continually changing.
Greenwich Hour Angle (GHA). As discussed above, the angle between two meridians of Longitude can be expressed as an hour angle. The hour angle between the Greenwich Meridian and the meridian of a celestial body is known as the Greenwich Hour Angle.


Rules for calculating LHA:
Long East, LHA = GHA + LONG (- 360o as necessary)
Long West, LHA = GHA – LONG (+ 360o as necessary) Example 1. : If Long. is 90oE. and GHA is 300o
Then LHA = GHA + LONG -360o
= 300o + 90o = 390o – 360o = 30o
Example 2: if Long. is 90oW. and GHA is 45,o we have:
LHA = 45o – 90o = -45o + 360o = 315o
Example 3: If your longitude is 35o 46’ East and the GHA of Mars is 39o 53’.8. What is the LHA?
Remember the rule: Long East, LHA = GHA + LONG (-360o )
GHA = 39o 53’.8
LONG = 35o 46’.0E (+)
LHA = 75 o 39’.8 .
(Remember 60 minutes in 1 degree)
Example 4. Your assumed longitude = 125o 13’.0W. The GHA of the Sun is 243o 44’.7 What is the LHA?
Long West, LHA = GHA – LONG (+360o ?)
GHA = 243o 44’.7
LONG = 125o 13’.0W (-)
LHA = 118o 31’.7
Example 5.
Longitude is 120oW. GHA is 70o.
What is the LHA?
LHA = GHA – LONG (+360o ?)
GHA = 70o 00’.0
LONG = 120o 00’.0 W. (-)
LHA = -50o 00’.0
360o 00’.0 (+)
LHA = 310o 00’.0
Example 6. Longitude is 90oE. GHA is 340o
What is the LHA?
LHA = GHA + LONG (-360o ?)
GHA = 340o
LONG = 90oE (+)
LHA = 430o
360o (-)
LHA = 70o

[Sjizzle]

u can read more here

[palmic]

Originally Posted by Sjizzle

If the time at an observer’s position is 2 hours and 3 minutes after noon, then the angular distance between the observer’s meridian of longitude and the Greenwich Meridian must be (2 x15o ) + (3x 15’) = 30o 45’. Because it is after noon at the observer’s position, the longitude of that position must be to the East of the Greenwich Meridian since the Earth rotates from West to East. Therefore the observer’s longitude must be 30o 45’ East and since LHA is measured westwards from the observer’s meridian, the LHA must also be 30o 45’.

Thank you Sjizzle this explained everything to me, i am sure it will help the others too, if they'll find it!

I would just complain this approach as main description for get longitude in your post #2, because its not clear how that spreadsheet calculates it and its not IMO realistic to use excel in 1939

[Sjizzle]

Originally Posted by palmic

Thank you Sjizzle this explained everything to me, i am sure it will help the others too, if they'll find it!

I would just complain this approach as main description for get longitude in your post #2, because its not clear how that spreadsheet calculates it and its not IMO realistic to use excel in 1939

my pleasure also i have posted a link for the celestial fix basics see the post above

[palmic]

Yeah, read it, thanks!

I made printable cheatsheet to get into it easily without need to alt-tab out of the game

[Sjizzle]

@palmic take a look here how to navigate without navigation officer ....i calculated my own position


PS. i don't use TDW's UI

[siege00]

Any chance of someone doing a Celestial Nav step by step tutorial?

[Sjizzle]

Originally Posted by siege00

Any chance of someone doing a Celestial Nav step by step tutorial?

read the first posts of this thread !!

[siege00]

Originally Posted by Sjizzle

read the first posts of this thread !!

Sorry Sjizzle, I should've been more specific. The noon sightings I understand... it's the Stars, Planets, Moons stuff that makes me scratch my head. I'll have to keep watching those vids, which are really good, until it sets in.

From a procedures standpoint, do you just operate via the noon-time fix and DR? And does that work pretty well for the most part? I'm wondering if drift, currents, etc. are built into the game, TWoS specifically.

Thanks!

[Sjizzle]

Originally Posted by siege00

Sorry Sjizzle, I should've been more specific. The noon sightings I understand... it's the Stars, Planets, Moons stuff that makes me scratch my head. I'll have to keep watching those vids, which are really good, until it sets in.

From a procedures standpoint, do you just operate via the noon-time fix and DR? And does that work pretty well for the most part? I'm wondering if drift, currents, etc. are built into the game, TWoS specifically.

Thanks!

heya.... yup i make 2 celestial fix a day 1 noon and 1 at the midnight using the stars but for the stars celestial fix i didn't made a tutorial was busy in RL and also completely forgot about it ..... u can really lost yourself on the sea when is bad weather cos there is no sun and u must make a DR fix and sometimes is hard to keep the heading cos u drift out from the course .....

[siege00]

Gotcha. How often do you miss your fixes? ie. scattered clouds making you miss the sun overhead, or bad weather? Have you had to go long times with no fixes? That actually sounds kinda fun, but could be a little frustrating. lol

[palmic]

Is it possible to make fix by polar star here?
It should be easiest way isn't?

Thanks for all your work, this is one of best mods ever