Picture talking
• Can you identify the
devices in the picture?
• What are their uses on
board ship respectively?
Chapter 7
• Introduction
This chapter presents the basic features and
working principles of major navigational
instruments used onboard, which is crucial to
the safe and efficient navigation on the sea.
It should be borne in mind that no single
navigational aid should ever be relied upon as
the exclusive method for navigating your vessel.
The
navigator
is responsible
forused
checking
all aids
Various
navigational
aids should be
in a combined
available
to aconfirm
position.
Electronic
aids
operation on
vessel tohis
ensure
the safety
of navigation.
are meant to assist the navigator, not replace
him.
The contents:
• Radar & Radar Plotting (2 teaching
segments/4hrs)
• Magnetic Compass & Gyro Compass(2
teaching segments/4hrs)
• GPS, VDR, AIS, ECDIS(2 teaching
segments/4hrs)
Lesson Components:
• Introduction
• Vocabulary
• Text Study
• Review
Part I Radar
I. Vocabulary Study
radio detection and ranging (radar)
crucial / k̍ ruʃəl /adj. 对……很重要的，关键的
Speed
is crucial
to ouradj
success.
exclusive
/iks
̍klu:siv/
. 唯一的
Radar is crucial to the safe navigation at sea.
transmitter
e.g. The cabinn.is发射机
for the exclusive use of Master.
pulse /pʌls /n. 脉冲
pulse length脉长/ pulse width脉宽/ pulse duration
modulate / ̍mɔdjuleit/ vt. 调节
e.g. In marine navigation application, the radar signal is
pulse modulated.
在海上导航的应用中，雷达信号是脉冲调制的。
• low average power普通低电压
Strong signals
can be provided
with low average power
• Plan Position
Indicator
（PPI）平面位置指
The示器
plan position indicator (PPI), is the
most
commonadj.
type of射线的
radar display.
The to rays of light , beams of light
relating
radial
radar antenna is usually represented in the
center
of the display,
so the distance from it
radial
line辐射线
and height above ground can be drawn as
synchronize
vtradar
. 调整……使其同步
concentric
circles. As the
antenna
synchronization
. 同步
rotates,
a radial line on the n
PPI
sweeps in
synchronization
it /
about
the̍ncenter
e.g. If therewith
is any
difference
between
the
readings of master
luminescent
lu:mi
esnt
/
adj
.
发光的
point.compass and its repeater, make sure to synchronize them.
Payment willtube
be proportional
to the amount of work done.
luminescent
发光管，冷光管
On a PPI, a target’s actual range is proportional to its echo’s
A detection
is indicated
by
brightening
proportional
adjscope’s
. a成比例的
distance
from the
center. of the screen at the bearing
and range of the return. Because of a luminescent tube face coating,
be
proportional
the glow
continues afterto
the与……成比例
radial line rotates past the target.
•
•
•
•
A ship's head up (un-stabilized)
display
has the
heading
• cursor
n.ship's
指针
moveable cursor移动光标
marker fixed at 0°，at the top of
•theheading-upward
A moveable
cursorpresentation首向上显示模式
helps
to
screen．All
targets，fixed
or
moving，move
relativepresentation
to thebearings. 北向上显示模式
measure ranges
and
• north-upward
ship's position in the centre of the
•screen
unstabilized
adj
. 不稳定的 反义词：stabilized
and the heading
marker．As
thee.g.
ship In
moves
the water，
thethrough
stabilized
“north-upward”
presentation, gyro
•fixed
orientation
/ɔ:rien ̍teiʃən
/n. 定向，方向
targetsnorth
appear is
to track
down
always
at
the
top of the scope.
(position
relative
to
points
of
the
compass)
the screen on a reciprocal heading
at
the speed
the ship
is moving and presentation, the
e.g.
In this
unstabilized
when the ship alters course, targets
orientation
changes
appear
to rotate in the
opposite as the ship changes heading
direction to that of the ship，so
targets appear to move on the radar
screen while the ship's heading
remains fixed．
II. Passage Reading
Warming-up Questions:
1. Which measurement of radar is more accurate,
bearing or distance?
2. What is the PRR of a radar signal?
3. Can you name radar components?
4. What is the most common type of radar
display?
5. Which presentation is stabilized, headingupward or north-upward?
• Passage
one
A directional antenna or beam antenna is an antenna which radiates
greater power in one or more directions allowing for increased performance
• General
Characteristics
on transmit and receive and reduced interference from unwanted sources. All
practical antennas
are at least somewhat
directional.方向或定向天线对于空
Radar
determines
distance
to an object by
间不同的方向具有不同的辐射或接收能力，在水平面上，有一个或多
measuring
the time required for a radio signal
个能量较集中的方向，抗干扰能力比较强。实用天线都略带方向性。
to travel from a transmitter to an object and
return. Since most radars use directional
antenna
, they
can also
determine
an object’s
Radar
determines
distance
to an object
[by
bearing.
However,
radar’s
bearing
measuring
theatime
(required
for a radio
signal to travel
from
transmitterthan
to anits
object
measurement
will be
lessa accurate
andmeasurement.
return.)]
distance
Understanding this
Theisdistance
from
a ship tothe
an object
can be
concept
crucial to
ensuring
optimal
calculated by counting the cycle time taken by
employment of the radar for safe navigation.
a radar signal.
1.1 Signal Characteristics
时标电路（脉冲发生器）通过天线辐射窄脉冲能量产生信号。so that 引导结
果状语
In most marine navigation applications, the radar signal is pulse
modulated. Signals are generated by a timing circuit so that
energy leaves the antenna in very short pulses. When transmitting,
the antenna is connected to the transmitter but not the receiver.
As soon as the pulse leaves, an electronic switch disconnects the
由于脉冲之间的时间间隔比一个脉冲的长度要长，强信号可以用普通低电压来发
antenna from the transmitter and connects it to the receiver.
送。
Another pulse is not transmitted until after the preceding one has
Since 引导一个原因状语从句，interval这里指时间间隔。
had time to travel to the most distant target within range and
return. Since the interval between pulses is long compared with
the length of a pulse, strong signals can be provided with low
average power. The duration or length of a single pulse is called
pulse length, pulse duration, or pulse width. This pulse emission
sequence repeats a great many times, perhaps 1,000 per second.
This rate defines the pulse repetition rate (PRR). The returned
pulses are displayed on an indicator screen.
1.2. The Display
In synchronization with与…保持同步
the clock
inused
synchronization
withisthe
internet.
The most commone.g.
type Set
of radar
display
in the navigation
the plan
position
indicator (PPI). On a PPI, the sweep starts at the center of the display and moves
outward along a radial line rotating in synchronization with the antenna. A detection is
indicated by a brightening of the display screen at the bearing and range of the return.
Because of a luminescent tube face coating, the glow continues after the trace rotates
past the target.
探测（到的目标）以亮点的形式显示在回波的方位和距离处。由于冷光管表
面有涂层，扫描线扫过目标后，仍能看见亮光。bearing方位 range距离、量
程
On a PPI, a target’s actual range is proportional to its echo’s
distance from the scope’s center. A moveable cursor helps to
在平面显示器上，目标的实际距离与
measure ranges and bearings. In the
“heading-upward”
回波到显示屏中心的距离成正比。
scope = radar display screen 显示屏
presentation,
which
indicates
relative
bearings, the top of the
距离和方位（极坐标）
scope represents the direction of the ship’s head. In this
unstabilized presentation, the orientation changes as the ship
changes heading. In the stabilized “north-upward” presentation,
gyro north is always at the top of the scope.
在首向上显示模式中，雷达指示的是
相对方位，显示屏顶端代表了船首向。
由于这种显示模式不稳定，方位会随
着船首向的变化而变化。
常见显示模式的还有：head-up
cg(cursor gyro) mode, course-up
mode, north-up true motion
Language points to remember:
• Radar, transmitter, receiver, antenna, screen(scope), sweep,
bearing, range
•
•
•
•
•
•
•
•
•
•
•
•
雷达、发射器、接收器、天线、屏幕、扫描（线）、方位、距离/量程）
时标电路
timing circuit
be crucial to
对…很重要；关键
exclusive
专门的
脉冲调制的
pulse modulated
Pulse length/pulse duration/pulse width
脉长/宽
PRR---pulse repetition rate
脉冲重复率
PPI---plan position indicator
平面位置显示器
in synchronization with
与…同步
be proportional to
与…成比例
moveable cursor
移动光标
heading-upward presentation; north-upward presentation
首向上显示、北向上显示
stabilized; unstabilized
稳定；不稳定
Home Work:
• Be capable of using key words and
expressions in this lesson
• Be able to express the ideas about radar
in English
• Look up the words which are new to you
in the dictionary and read the text globally
for main ideas