                       H.O 211 LINE OF POSITION WORKSHEET

           Section a (time)                      Section b (sextant)

        Date        ____d____m______y     Sextant Angle  ___________'
                                              (SA)
        Watch time  ____h____m____s       Index Error   ___________'
                                              (IC)
        Corrections:                      Refraction          -______'
        Chg to 24 hr____h____m____s
                                          Dip                 -______'
        Watch error_________m____s
                                          Semi-diameter       +______'
        Time zone  ____h____m              (- for upper limb)
                                          Parallax corr.      +______'
        GMT         ____h____m____s         (moon only)
                                          Ho             ___________'


           Section c (from almanac)                   Comments

        Declination ___________'  d____   __________________________________

        Interp.          ______'        ____________________________________
         (from table)
        True Decl.  ___________'        ____________________________________

        GHA         ___________'        ____________________________________
                                         
        Interp.    +___________'        ____________________________________
         (from table)                                
        True GHA    ___________'        ____________________________________

                                         ____________________________________

        Section d (sight reduction)

             col I                 col II      col III     col IV      col V
     Est Lon    ___________'  (+ if Lon east of Greenwich, - if Lon west)

     LHA         ___________'  (if < 0, add 360) 
                                        
     t           ___________'->A _______    (LHA if < 180, else 360-LHA)

     True Decl.  ___________'->B+_______    A _______
     (from sec c)                         
                                A _______ -->B-_______   B _______  A _______

     K           ___________'     <-------- A _______
                                (if t > 90 then K > 90)
     Est Lat    ___________'  (- if decl same name as lat, + if contrary)

     K  Est Lat ___________'     -------->             B+_______
     (take abs)
     Hc          ___________'                <-------   A _______->B-_______

     Ho         -___________'      (Ho greater: toward;  Hc greater: away)
     (from sec b)
     delta       ___________'  mi  toward|  Zn_____    Z_____ <--A _______
                                    away  |

                               H.O 211 Instructions

        1) Record Date and Time of sight in top 2 lines of section a

        2) Record sextant data top line of in section b

        3) Enter correction to time in section a

        4) Sum corrections to arrive at GMT in last line of section a

        5) Enter index error, refraction, and dip corrections in section b

        6) Look up semi-diameter in almanac and enter in section b
           (sun and moon only)

        7) Look up parallax correction in parallax table and enter in section b
           (moon only)

        8) Sum corrections to arrive at Ho in last line of section b

        9) Look up time and date in almanac to the nearest hour of GMT
           and record GHA and Declination of sighted object in section c

        10)Lookup interpolation values for GHA and Declination in appropriate
           tables using the remainder minutes and seconds of GMT.  Enter
           these corrections in section c

        11)Sum corrections to Declination and GHA to get True Decl. and True
           GHA.  Enter these into section c

        12)Enter your estimated longitude into section d.  Sum as indicated
           to GHA to get LHA and enter this into section d.  Now carry LHA
           into the blank marked t in section d, doing the necessary
           conversion as shown to the right

        13)Look up t angle in H.O. 211 table and record the A value in col II

        14)Copy True Decl. from section c to section d.  Look up True Decl.
           angle in table.  Enter B value in col II and A value in col III

        15)Add col II values and enter sum in blank provided in col II.  Also
           copy the sum into col V

        16)Find the sum in col II as an A value in table.  Enter the associated
           B value into col III and col IV.  If the sum falls in between two
           widely spaced A values in the table, it may be necessary to
           interpolate between the corresponding values of B.  It is important
           that this B value be accurate.

        17)Subtract B value in col III from A value in col III and enter the
           difference in the blank provided in col III

        18)Find the difference in col III as an A value in the table.  Enter
           the associated angle in col I in the blank marked K.  Observe that
           if t in col I is > 90 then use the angle K in the table that is
           also > 90.  If t < 90, use K < 90


        19)Enter your estimated latitude in the blank provided in col I

        20)Compute the sum or difference as indicated of K angle and Est Lat.
           Enter the result in the blank indicated in col I.  If result < 0,
           drop the sign (that is if Est Lat > K, subract K from Est Lat).

        21)Look up K  Est Lat in the table.  Enter the B value in col IV

        22)Sum the two values in col IV and enter the result in the blank
           provided

        23)Find the sum in col IV in the table as an A value.  Enter the
           associated B value in col V and the associated angle in col I in
           the blank labeled Hc (Hc always < 90)

        24)Subtract the B value in col V from the A value in col V and enter
           the result in the blank provided in col V

        25)Find the difference in col V in the table as an A value.  Enter the
           associated angle in the blank marked Z.  Observe the following
           quadrant rules carefully:  If t > 90, then always use Z < 90. 
           Otherwise, if you used the sum in step 20, then always use Z > 90. 
           If you used the difference in step 20, then if Est Lat < angle K,
           use Z > 90, else use Z < 90

        26)To determine Zn: If you are in the northern hemisphere and
           LHA < 180, Zn = 360 - Z, else Zn = Z.  If you are in the southern
           hemisphere and LHA < 180, Zn = 180 + Z, else Zn = 180 - Z

        27)Enter Ho from section b into the blank provided in col I.  Enter
           the difference between Hc and Ho to obtain your delta miles.  Enter
           this value in the blank provided in col I

        28)Go to a plotting sheet.  Your estimated position (Est Lon & Est Lat)
           is at the center of the compass rose.  Plot an azimuth line through
           the center of the rose that passes through the value of Zn on the
           rose.  This line should extend in both directions from the center
           of the rose.  Now write the name of the object sighted along with
           the GMT of the sighting next to the Zn value on the rose

        29)Use the scale on the vertical axis to set your dividers to the value
           shown as delta in col I of your worksheet

        30)Use the dividers to measure that distance along the azimuth line
           from the center of the rose.  If Ho > Hc in col I of your worksheet,
           measure toward the sighted object.  If Ho < Hc, measure away.
           Mark this spot on the azimuth line

        31)Draw a line of position (LOP) that passes through the point you
           just plotted in step 30 and is at right angles to your azimuth line.
           Label it as an LOP and include the name of the object sighted and
           the GMT of the sighting.  Your position at that time is somewhere
           along that line


        32)Sight another object, or wait a while (at least an hour) and sight
           the same object again.  On a separate worksheet, repeat steps 1
           through 27.  Be SURE to use the same Est Lat and Est Lon as you did
           on the first worksheet.  Repeat steps 28 through 31 on the same
           plotting sheet

        33)If you have not moved significantly during the time elapsed between
           the two sights, your position is where the two LOPs intersect and
           you may skip to step 39

        34)Draw a line through the center of the rose that also passes through
           your course heading on the rose.  Extend this line so that it
           intersects your first LOP.

        35)Find the product of your speed (in knots) and the time elapsed
           between sightings (in hours)

        36)Use the scale on the vertical axis to set your dividers to the
           product arrived at in step 35

        37)Use the dividers to measure that distance from the intersection
           point identified in step 34 along your course heading line, but in
           the opposited direction as your heading.  Plot a point there

        38)Use parallel rules to slide your FIRST LOP so that it passes through
           the point you plotted in step 37.  Label it ADJ LOP

        39)Where your second LOP intersects your ADJ LOP (of if you skipped
           steps 34 through 38, where your second LOP intesects your first) is
           where you are.  How much your estimated position is in error
           is indicated by the distance and direction this intersection point
           is in relation to the center of the compass rose.  Use your dividers
           to measure your error in latitude by setting them to the vertical
           distance between the center of the rose and the intersection point.
           Measure this along the vertical axis.  Do the same horizontally to
           measure your error in longitude, but this time, instead of using the
           scale along the vertical axis, measure it using the latitude
           correction scale at the corner of your plotting sheet.

        NOTE: If you plot more than two LOPs, use the same Est Lat and Est Lon
        on all of the work sheets.  All of the LOPs except the last must be
        slid the appropriate amount (computed using steps 34 through 38 but
        in each case using the time elapsed from the sight involved until the
        last sight).

