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Ap Volume - Rapid Sight Reduction Form333: Observations of

This document appears to be instructions for completing a rapid sight reduction form to determine the position of a vessel at sea. It outlines 8 steps: 1) Estimating initial position, 2) Converting dates and times to Greenwich date and Universal Time, 3) Determining Greenwich Hour Angle, 4) Calculating Local Hour Angle, 5) Correcting sextant altitude observations, 6) Extracting tabulated altitudes and azimuths, 7) Calculating intercepts, and 8) Applying corrections for vessel motion, body motion, and precession/nutation to determine the final intercept. The form is used to calculate the vessel's position through celestial navigation techniques.

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thugsdei
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105 views1 page

Ap Volume - Rapid Sight Reduction Form333: Observations of

This document appears to be instructions for completing a rapid sight reduction form to determine the position of a vessel at sea. It outlines 8 steps: 1) Estimating initial position, 2) Converting dates and times to Greenwich date and Universal Time, 3) Determining Greenwich Hour Angle, 4) Calculating Local Hour Angle, 5) Correcting sextant altitude observations, 6) Extracting tabulated altitudes and azimuths, 7) Calculating intercepts, and 8) Applying corrections for vessel motion, body motion, and precession/nutation to determine the final intercept. The form is used to calculate the vessel's position through celestial navigation techniques.

Uploaded by

thugsdei
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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AP VOLUME RAPID SIGHT REDUCTION FORM 333

Estimated position at the time of x: Navigator


 
DR/EP: Lat. Long. Height of eye m/ft
. on arc
Convert Dates/Times: Year month d h m s Index Error off arc +

Fix, local date and time Course T Temp. C/F
Zone correction, W + ZT Speed kn Pressure mb/in
E
Greenwich date & UT UTf Depart To
Observations of
Local date
h m s h m s h m s h m s

Local watch time DWT


fast
Watch error, slow + DWE
Local time
Zone correction, W + ZT
E
UT (Greenwich date) UT ( ) ( ) ( ) ( )
UT of Fix UTf
later +
Fix earlier UTf UT
GHA: Table :    

Greenwich date (year, mth, ) ( )


d
Day and hours (b)
Minutes and seconds (c)

Sum = (a) + (b) + (c) GHA


AP longitude, E +
W
Sum
if required

GHA + AP Long LHA
Correct sextant altitudes:        

Sextant altitude Hs
on arc
Index error, off arc + IE
Dip, Table a (ht m/ft) D
Sum IE + D
Apparent altitude Ha
Refraction, Table b (Ha ) R

and Table c (T, P, Ha ) ( , ) ( , ) ( , ) ( , )
Observed altitude Ho
Extract tabulated alt/az:

(AP latitude, LHA) Hc ( , ) ( , ) ( , ) ( , )
Intercept = Ho Hc p

Azimuth Zn
(a) Motion of vessel:
if required
True track of vessel C
Zn C Rel.Zn
Table (DMG,Rel.Zn ) MOO ( nm) ( nm) ( nm) ( nm)
(b) Motion of body:Table m s m s m s m s

(Lat, Zn ), UTf UT MOB


(c) Precession & nutation:
Table , (year, Lat, LHA)
Intercept, corrected
+ towards p
away

Azimuth (step ) Zn
c
HMNAO CCLRC

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