Quote:
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