1- More accurate
QM's (Quartermaster) and
OS's (Operation Specialist, formerly RD, Radar operator) are
required to independently fix the ship's position and compare
When offshore Bridge and
CIC (Combat Information Center) fixes
seem to agree, however, when close to shore or during Nav Detail
there are disagreements between the bridge and CIC. So who
is really correct? The answer is, both and neither. The
problem is with scale.
When offshore both QMs
and OSs use the latitude scale of the chart to measure range for
The problem comes when we come close to land.
Harbor charts conveniently provide scales in yards, miles and
nautical miles, but, they are not the same scale used by
radars. I thought there had to be a common
measurement in order to make things work.
Where as: radars
display range as 2000 yd = 1 nautical mile.
And where as: 1' (or 60") of latitude = 1 nautical mile.
Therefore: 1' (or 60") of latitude = 2000yd.
If we work the math
further we find that;
1/2 nautical mile or 1000yd = 30" of latitude
1/4 nautical mile or 500yd = 15"of latitude
100 nautical yd = 3" of latitude.
At the smallest unit 1 nautical yd = .03" of latitude.
If both bridge and CIC
constructed range scales based on the latitude scale onto margin
of the harbor charts, the radar fixes will become far more
accurate and will agree with bridge visual fixes.
When plotting areas on a
chart such as mine fields, amphibious boat lanes, etc. simply
convert yards to minutes of latitude and then use the latitude
scale of the chart to measure those distances on the chart.
For example: You are
required to measure 1568 yd.
Just multiply 1568yd x .03 which equals 47.04" of Lat.
The Lat scales on harbor
charts will let you measure that close.
increased accuracy is incredible!
2 - Instant Plotting and Quick Bearing and
When piloting, the
bearing and range to a navigation aid or hazard is often
required and must be determined quickly.
For many decades RD's
and OS's have used a scaled PMP
blade for quick plotting on the DRT
plotting table. Bridge personnel can do the same thing
with their charts.
Construct chart scales
on plain paper using the Lat scales as mentioned above. Use some art work and make
your scales look similar to those printed on the charts.
The nicer your scales look, the easier they are to use.
Label the scales with the chart scale and common
chart numbers that use that scale. Tape the scale to the
underside of a clear plastic PMP blade. Create more so you
have a collection of PMP blades with various scales, one for
each of your usual harbor charts.
When bearing and range
are needed, simply lay down the PMP blade and read the
results. Bearing and range are read in one motion.
No more reaching across with dividers.
REMEMBER!!! When you shift charts, don't forget to change to
the PMP blade to the matching chart scale!
How this idea came
incorporated the idea of using a scale on my PMP blade while
performing PCS/UW (Primary Control Ship/Underway) during
Amphibious RefTra (Amphibious Refresher Training) aboard USS
Durham (LKA-114) in 1982.
For those who have never done it, it is a very
The bridge is required to visually fix the ships position every
30 sec. After each fix, bridge then plots a 30 sec DR for
the next fix. A bearing and range from that DR to the
right flank of boat lane is reported to CIC. CIC then
plots that DR position on their chart. By then the 30 sec
has elapsed and based on the DR, CIC uses radar bearing and
range to fix the position of the wave commander in the boat lane
and then directs the wave commander to come right, come left,
speed up, or slow down, etc. This procedure is repeated
every 30 sec while the ship maneuvers to maintain the best
defensive aspect to the beach. Object: Direct
landing craft to the beach so that they drop ramps exactly at H
hour, +/- 30 sec.
No one told me how to do this. I just taped to a scale to
the PMP blade, using scales as mentioned above, and instant
plotting of the DR and the instant reading of bearing and range
to the boat lane became literally a flip of the wrist!
Using these techniques, USS
Durham passed Amphib RefTra with blazing scores. (I
was never recognized for my innovation.)
From an amphibious
ship I was transferred to a Minesweeper and minefield
navigation presented a very similar problem.
I used the same
techniques to layout mine fields and then navigated through
them and plotted mine positions with extreme precision
during MRCI (Mine Readiness Certification
Inspection). USS Excel passed MRCI with such
blazing scores that I was awarded a Navy/Marine Corps Achievement
Medal from MineGruOne for my innovation.
On Excel I
was relieved by my good friend, Rick Burris, and I showed
him my technique. He then used it while conducting
mine sweeping operations in the Persian Gulf and was also
awarded Navy/Marine Corps Achievement medal.
How to Shoot More Accurate
Most LOPs (lines of Position) rarely
intersect to form a perfect asterisk, which leaves the
navigator to interpenetrate the fix, but there is an easy way
to eliminate a simple error.
DIP is the correction for height of eye above the sea.
Most Navigators have the measured their height of eye while
pier side, but, that height changes when at sea. In a
relatively smooth 10 foot sea, ask your self, did I shoot at
the top or the bottom of the wave? It makes a real
difference in computing HO and can throw off an LOP by more
than a few miles. The elimination of this shooting error
is easy. Just show up early to shoot and just relax.
It is how you relax that makes the difference. Lean
against a bulkhead for 5 min or more and just feel the motion
of the ship. You will notice a pattern in the ships
motion, up, down, right, left hard up, down, right left,
etc. Within that pattern there will be a few seconds
when the ship sits perfectly still. (To me the ship goes
"mush") That is the moment the ship is sitting at zero -
perfect sea level - and your measured DIP is correct.
While shooting, feel the pattern of the motion of the
ship. Wait for the "mush" and that is when you
"Mark!" Do this and your fixes will tighten up.
I was on an
undermanned ship and often didn't have anyone to record for me
so I developed these procedures. They actually work
How to Shoot Celestial by
Sun lines are easy. Hold a watch in your hand.
When you "Mark" take your hand off the sextant and remember
the time on the watch. (Seconds is the important
part) Write down the time you remember and then then
read the hs off the sextant.
LAN is a little harder. The thing to remember is that
you are observing the sun as it rises. Each time you
observe the sun go up, adjust the hs and note a new time.
(Only min and sec) When the sun dips down do nothing -
Take your hand off the sextant. Adjust the sextant and
note a new time ONLY while the sun continues to
rise. When it is obvious that the sun is on the way
down, you are done. Write down the last time remembered
and read hs off the sextant. That is LAN
Morning and evening stars requires the use of a small personal
recorder. (A mike clipped to the collar makes it better)
Prepare the shot and then start the recorder. Do NOT
turn it off and start talking to yourself. Talking out
loud perform a time. "At the mark the time will be . .
." Then start talking to yourself. "OK,
coming out on the bridge wing. Hm, a little early.
Stars should start coming out to the east next. Should
see Arteries. It should be just abaft the beam.
OK, there it is. Got a horizon. OK, Ive got it . .
. ready . . . Standby . . . MARK!" Now wait a few
moments, then read the hs and move on to the next star.
Back in the chart room replay the recorder. Now you are
playing the role of celestial recorder. Listen to the
time tick and start a stop watch. Listen and write down
the "Mark" times and the corresponding hs.
It does take a little longer, but, you have the shot.