Crow's Nest

The raven, or crow, was an essential part of the Vikings' navigation equipment. These land-lubbing birds were carried on aboard to help the ship's navigator determine where the closest land lay when weather prevented sighting the shore. In cases of poor visibility, a crow was released and the navigator plotted a course corresponding to the bird's flight path because the crow invariably headed towards land. 

The Norsemen carried the birds in a cage secured to the top of the mast. Later on, as ships grew and the lookout stood his watch in a tub located high on the main mast, the name "crow's nest" was given to this tub. While today's Navy still uses lookouts in addition to radars, etc., the crow's nest is a thing of the past.

International code of signal and their alphabetic equivalent

Each flag represents a letter or number and can spell out a word or messsage. Each alphabetic flag can also mean a common word or phrase.

letters	phonetic alphabet	meanings
A	Alfa	Diver below, OR undergoing speed trial
B	Bravo	taking or discharging explosives
C	Charlie	Affirmative/Yes
D	Delta	Keep clear; Maneuvering with difficulty
E	Echo	Altering course to starboard
F	Foxtrot	Disabled, communicate with me
G	Golf	Need a pilot
H	Hotel	I have a pilot
I	India	Altering course to port
J	Juliette	I will send you message by semaphore; On fire with dangerous cargo, keep clear
K	Kilo	You should stop your vessel instantly. Wish to communicate
L	Lima	You should stop, I have something important to communicate
M	Mike	I have a doctor on board. Stopped and makingno way through the water
N	November	Negative/No
O	Oscar	Man overboard
P	Papa	"The Blue Peter" All aboard, vessel is about to proceed. At sea: your lights are out or burning badly
Q	Quebec	My vessel is healthy and I request free practique
R	Romeo	The way is off my ship. You may feel your way past me
S	Sierra	My engines are going full speed astern
T	Tango	Do not pass ahead of me, Keep clear, engaged in pair trawling
U	Uniform	You are coming into danger
V	Victor	I require assistance (not distress)
W	Whiskey	I require medical assistance
X	X-ray	Stop what you're doing and watch for my signals
Y	Yankee	I am carrying mails; dragging my anchor
Z	Zulu	To be used to address or call shore stations. Require tug

Flags codes

signal flags	meanings
NC	I am in distress
AC	I am abandoning my vessel
AN	I need a doctor
BR	I require a helicopter
CD	I require immediate assistance
DV	I am drifting
EF	SOS/MAYDAY has been canceled
FA	Will you give me my position?
GW	Man overboard. Please take action to pick him up
JL	You are running the risk of going aground
LO	I am not in my correct position: used by a light vessel
PD	Your navigation lights are not visible
PP	Keep well clear of me
RU	Keep clear of me; I am maneuvering with difficulty
QD	I am going ahead
QQ	I require health clearance
QT	I am going astern
QU	Anchoring is prohibited
QX	I request permission to anchor
SO	You should stop your vessel instantly
UM	The Harbor is closed to traffic
UP	Permission to enter Harbor is urgently requested. I have an emergency
YU	I am going to communicate with your station by means of the International Code of Signals
ZL	Your signal has been received but not understood.