Interpolation in Pub.229

[Rumata]

Let me clarify one thing...  I didnt mean to imply that AP should be as close to the DR as possible - I meant to say that I like to choose an AP whose ZN lays as close to DR as possible..  One thing is not the other.

In your example you said the assumed lat is 5-52.9.  This is wrong because your assumed lat should be a whole number closest to DR - in your case you mean Longitude i think...  Anyway you can choose AP Long 4-52.9 instead to get you closer to DR if THAT ZN also comes closer to DR.  It appears in your example that you are talking about a late morning shot.... I would use the closest lat whole number north and the 4-52.9 for AP Long; this would put the DR between the AP and the body. (Im not sure what your Lat is)  Then your LHA would be 329.  Im thinking that unless your DR is near DEC your ZN will be something like 160 or 170.

Dont be afraid of big intercept numbers.  I recently had an intercept of 52.? that put me and the ZN within a mile or two of my exact Position using a Gunter quadrant variant.

good luck
joe

Joe, I think I didn't express myself clear enough. In my previous posts by a typo I put Lat, where it should be Long. Yes, you are right, for the assumed Lat. one needs to take the whole number. Any Publications requires the whole number for Lat. But, when you calculate LHA, which is in my case  LHA=GHA+Long., ( long.. is E and I need to get LHA as a whole number. So, when I tried to use 4 deg Long. instead of 5 deg. I got LOP so far away from two other Sun shots, one can't reach it with a  six feet pole. And, also, you're right, that I kinda afraid of big intercepts. When I got an intercept close to almost one degree-I think I did wrong.

Well, practice makes us sane. ;>

Thank you

LOL... Now I am very interested in your work... I also live in E long and add AP to GHA.  Please send me two or three of your observations and let me try to work them... :)  please include the body, gmt time, gmt date, DR, HS, IE, dip, and  any other data you think I need.

thanks
joe

Joe, thank you for your interest.

The data corresponds to the hypothetical situation 12/18/1993..I just "polish" my basic knowledge, that's it ;>

Sun GMT 13-45-23   Hs 19-16.2
Sun GMT 13-47-02   Hs 19-07.8
Sun GMT 13-48-43   Hs 18-54.7

TC 120. V=6.5kn, DR @ 12-00 GMT 40-30N, 5-05E, IC=-1.0, Height of eye=10'.

One of the Sun sight appears ( in my cals of LOP) far away from the other two. But as soon as I used the interpolated data for Hc between 40 deg. Lat and 41 deg. Lat ( Z almost the same) I got much better result.

Moon sights  were very consistent:
Moon , UL 13-50-21  Hs 34-58.5
Moon        13-51-58   35-09.2
Moon       13-53-37   35-23.3


I got a fix.  But it is different from what it supposed to be. Not too much, but considering small distance traveled-appreciable ;>  And because. calcs were quite routine I wonder where did I screw up.

Well, I worked the first two sun shots and the first moon shot the long way; this is what I got:

Ships position at 13:50:21 GMT -  40:12.2N, 04:57.5E

This puts the DR 19 nm off; the true position is to the south-west.
I could clean this up a bit if I decrease the scale, but for fun this is close enough.  I thought I captured the numbering of meridians  in the photo but I missed...  The compass rose is centered at 40N, 06E.

Notice sun 1 and sun 2 LOPs are on top of each other - thats due to the close observations and the ship having the same true course as the LOP line.  The Moon 1 LOP then almost dissects the  sun 1 intercept.

Joe, thank you. My results were 40-10, 05-31.  Supposed to be 40-23, 05-17. But we are in the same hemisphere. Meaning, we are fine ;>