MOBOARD Flashcards
Advance
The distance a vessel moves in its original direction after the helm is put over
Apparent Wind
The speed and true direction from which the wind appears to blow with reference to a moving point.
Circle Spacing
The distance in yards between successive whole numbered circles. Unless otherwise designated, it is always 1000 yards.
Cone of Course
Mathematically calculated limits, relative to datum, within which a submarine must be in order to intercept the torpedo danger zone
Course
Direction of actual movement relative to true north
Datum
The last known position of an enemy submarine at a specified time. (Lacking other knowledge this is the position and time of torpedoing)
Direction
The position of one point in space relative to another without reference to the distance between them
Direction of Relative Movement
(DRM) the direction of movement of the maneuvering ship relative to the reference ship; the direction of the relative movement line
Distance Circles
Circles concentric to the formation center, with radii of specified distances, used in the designation of main body stations in a circular formation. Circles are designated by means of their radii, in thousands of yards from the formation center. Thus, circle 5 is a circle whose radius is 5000 yards from the center, while circle 7.2, is a circle 7200 yards from the formation center
Distance is Relative Movement
(MRM) the distance along the relative movement line between any two specified points or times
Fictitious Ship
An imaginary ship, presumed to maintain constant course and speed, substituted for a maneuvering ship which alters course and speed
Formation Axis
An arbitrarily selected direction from which all bearings used in the designation of main body stations in a circular formation are measured. The formation axis is always indicated as a true direction from the formation center
Formation Center
The arbitrarily selected point of origin for the polar coordinate system, around which a circular formation is formed. It is designated station zero
Formation Guide
A ship designated by the OTC as guide, and with reference to which all ships in the formation maintain position. The guide may or may not be at the formation center
Geographical (navigational) plot
A plot of the actual movements of objects (ships) with respect to the earth
Limited Lines of Approach
Mathematically calculated limits, relative to the force, within which an attacking submarine must be in order that it can reach the torpedo danger zone
Maneuvering Ship
Any moving unit set up in the problem except the reference ship
Missile Danger Zone
An area which the submarine must enter in order to be within maximum effective missile firing range
Range
Distance between ships
Reference Ship
The ship to which the movement of others is referred
Relative Distance
(MRM) The distance along the relative movement line between any two specified points or times
Relative Movement
The motion of one ship relative to another
Relative Movement Line
The locus of positions occupied by the maneuvering ship relative to the reference ship
Relative Plot
The plot of the positions occupied by the maneuvering ship relative to the reference ship
Relative Vector
A velocity vector which depicts the relative movement of an object (ship) in motion with respect to another object (ship), usually in motion
Relative Wind
The speed and relative direction from which the wind appears to blow with reference to a moving point.
Screen Axis
An arbitrarily selected direction from which all bearings used in the designation of screen stations in a circular formation are measured. The screen axis is always indicated as a true direction from the screen center
Screen Center
The selected point of origin for the polar coordinate system, around which a screen is formed. The screen center usually coincides with the formation center, but may be a specified true bearing and distance from it
Screen Station Numbering
Screening stations are designated be means of a station number, consisting of four or more digits. The last three digits are the bearing of the screen station relative to the screen axis, while the prefixed digits indicate the radius of the distance circle in thousands of yards from the screen center
Speed of Relative Movement
(SRM) the speed of the maneuvering ship relative to the reference ship
Speed Triangle
The usual designation of the vector diagram when scaled in knots
Station Numbering
Positions in a circular formation (other than the formation center) are designated by means of a station number, consisting of four or more digits. The last three digits are the bearing of the station relative to the formation axis, while the prefixed digits indicate the radius of the distance circle in thousands of yards. Thus station 4090 indicates a position bearing 90 degrees relative to the formation axis on a distance circle with a radius of 4000 yards from the formation center. Station 10.2340 indicates a position 10200 yards from the formation center bearing 340 degrees relative to the axis
Timeline
A line joining the heads of two vectors which represent successive courses and speeds of a specific unit in passing from an initial to a final position in known time, via a specified intermediate point. This line also touches the head of a constructive unit which proceeds directly from the initial to the final position in the same time. By general usage this constructive unit is called the fictitious ship. The head of its vector divides the time line into segments inversely proportional to the times spent by the unit on the first and second legs. The time line is used in two course problems
Torpedo Danger Zone
An area which the submarine must enter in order to be within maximum effective torpedo firing range
Transfer
The distance a vessel moves perpendicular to its initial direction in making a turn
True Vector
A velocity vector which depicts actual movement with respect to the earth
True Wind
True direction and force of wind relative to a fixed point on the earth
Vector
A directed line segment representing direction and magnitude
Vector Diagram
A graphical means of adding and subtracting vectors. When the vector magnitude is scaled in knots, this diagram is usually called Speed Triangle
Velocity Vector
A vector the magnitude of which represents rate of movement; a velocity vector may be either true or relative depending upon whether it depicts actual movement with respect to the earth or the relative movement of an object (ship) in motion with respect to another object (ship)
Wind Direction
The direction from which the wind blows
Wind Speed
The rate of motion of air
CPA
Closest Point of Approach
CWC
Composite Warfare Commander
DRM
Direction of Relative Movement
LLSuA
Limited Lines of Submerged Approach
LLQA
Limited Lines of Quiet Approach
LLSnA
Limited Lines of Snorkel Approach
LLSA
Limited Lines of Surface Approach
M
Maneuvering ship designation
MRM
Miles of Relative Movement
OTC
Officer of Tactical Command
R
Reference ship designation
RML
Relative Movement Line
SRM
Speed of Relative Movement
Relative Motion
Is motion with respect to an arbitrarily selected object
True Motion
Is movement with respect to the earth
e
Point of origin; fixed with respect to the earth
er
Reference ship vector designation
em
Maneuvering ship vector designation
rm
Relative movement vector designation representing SRM and DRM; always plotted in the direction M1 - M2
What are two types of bearings for indicating the direction of any object from another?
True Bearing
Relative Bearing
What are two points of reference are used to indicate bearings that never change?
The geographic North Pole for true bearing and the bow of our ship for relative bearing
True Bearing
Is the angular measurement between true north and the line of sight or line of bearing to an object. Always measured clockwise from north
Relative Bearing
Is the angular measurement between own ships head and the line of bearing to an object. It’s always measured clockwise from own ships head to the line of bearing or line of sight
What is the formula for calculating for True Bearing?
TB = RB + SH
TB = True Bearing RB = Relative Bearing SH = Ship Heading
What is the formula for calculating REaltive Bearing?
RB = TB - SH
RB = Relative Bearing TB = True Bearing SH = Ship Heading
What are your cardinal points?
North
South
East
West
What are your intercardinal points?
Northwest
Northeast
Southwest
Southeast
What is it called if it bears 000 degrees relative?
Dead Ahead
What is it called if it bears 045 degrees relative?
Broad on the Starboard Bow
What is it called when it bears 090 degrees relative?
Broad on the Starboard Beam
What is it called when it bears 135 relative?
Broad on the Starboard Quarter
What is it when it is bearing 180 degrees relative?
Dead Astern
What is it when it bears 315 degrees relative?
Broad on the Port Bow
What is it when it bears 270 degrees relative?
Broad on the Port Beam
What is it if it bears 225 degrees relative?
Broad on the Port Quarter
Target Angle
Is the relative bearing of your ship as seem from the target
What is the formula for Target Angle?
TA = TB + 180 - TC
TA = Target Angle TB = True Bearing 180 = Reciprocal Bearing TC = Targets Course
True or False
Motion is simply the movement of an object from one point to another
True
The change in positions in relations to a fixed reference point on Earth is known as _____________ movement.
True or actual
The movement that takes place between two ships when one or both are moving is known as ________________ movement
Relative
Which of the following is an example or relative motion?
A. A train traveling from Miami to Chicago B. A speeding auto passing a motorcycle C. A ship sailing around the world D. A person walking 5 miles E. All the above
B
Your own ship is on a course of 280 degrees true and lookout reports a contact bearing 350 degrees relative. What is the true bearing of the contact?
270 degrees true
Your course is 70 degrees true. Lookout report has a contact broad on the port quarter. What is the true and relative bearing of the contact?
295 degrees true/225 degrees relative
What is the reciprocal bearing of a contact that bears 260 degrees true?
080 degrees true
A contact bears 020 degrees true from own ship and is on course 270 degrees true. What is the target angle?
290 degrees true
The PPI scope is a presentation of _______________
Relative Motion
What is the formula to find a vessels speed?
S = D / T
If a ship travels 1500 yards in 5 minutes, what is it’s speed?
9kts
What is the formula for finding a ships distance?
D = S x T
If a ship travels 10 kts for 21 minutes, what is the distance will it have traveled?
7000 yards
What is the formula for figuring out time?
T = D / S
How long does it take a ship to travel 11200 yards at 14 kts?
24 minutes
What is the specific purpose of a maneuvering board?
It is specifically designed for solving problems relative motion
You are using the 2:1 scale for measuring distance. Each dot on the maneuvering board represents how many yards?
200
What is the distance scale would give you the largest plot of a contact having a range of 28800 yards?
3:1
What is the speed of a contact that travels 24000 yards in 40 minutes?
18kts
A contact traveling 12 kts in 25 minutes will travel a distance of ____________ yards.
10000
A contact that traveled at a speed of 16 kts and reached a distance of 32000 yards made its destination in ________________ minutes
60 minutes
The length of er vector represents own ships ______________
Speed
The initial mark of a contract is called _____________
M1
CBDR
Constant Bearing Decreasing Range
PAO
Past and Opening
What is determined by this paralleling a contacts relative movement line (RML) to the center of the maneuvering board?
DRM
The measured distance and elapsed time between the marks M1 and M2 determines the _______________
SRM
True or False
All vectors originate from the center of the maneuvering board?
True
The direction of relative movement (DRM) and the r-m vector are always drawn __________________
The same as the e-r vector
In the vector diagram, the direction of relative movement (DRM) and the speed of relative movement (SRM) determines the length and direction of the _______________ vector
r-m
Dead Time
Is the time between the time you decide to execute a maneuver and the actual time you begin the maneuver
MX
The point of execution for a maneuver on a MOBOARD
