Navigation Flashcards
What does the direction of the line joining the plots from M1 to M2 represent?
The direction in which the maneuvering ship (M) is moving with respect to the reference ship (R).
What is relative motion?
The motion of one object with respect to another object
How is DRM expressed?
True bearing
What is relative speed?
The speed at which the maneuvering ship is moving in relation to the reference ship.
What is DRM?
This direction of the maneuvering ship (M) moves in relation to the reference ship (R)
What is relative distance?
The distance the maneuvering ship (M) moves with respect to the reference ship in a given period of time
What is SRM?
The speed at which the maneuvering ship moves in relation to the reference ship
What is LRM?
This line starts at M1 and extends through M1, M2 and M3
How do you establish a object’s location geographically?
Use one reference line running in a N-S direction and another line in an E-W direction.
What is projection?
The grid lines on a sphere are round and navigational charts are flat. The process in which grid lines are transferred from a round surface to a flat surface is projection.
What are the two types of projection?
Mercator and gnomonic
What kinds of charts are the most common?
Mercator projection charts
What are the parallels on a chart?
Parallels are the latitude lines. They run E-W and become farther apart as their distance from the equator increases.
What are the meridians?
Meridians run N-S and are the longitude lines. They are parallel and equally distant from one another
What is 1 minute of latitude?
1 nautical mile
What is gnomonic projection?
Gnomonic projection preserves the curvature of the meridians and parallels.
What are polar charts normally in?
Gnomonic projections
What is each degree divided into?
60’ (minutes) or 3600” (seconds)
What is the reference line for all meridians?
Prime meridian
How many meridians does the charting grid have?
360 meridians
What is the reference for the parallels?
Equator
What is the latitude of a point?
The points angular distance in degrees, minutes, seconds of arc north or south of the equator, measured along the meridian that runs through the point.
What is 1’ (minute)?
It is 60 seconds.
Why do you use the latitude scale and not the longitude scale for measuring distance?
The parallels are always equidistant from each other, whereas meridians converge on the poles.
What is the scale of a chart?
The scale indicates the relationship between the size of a feature on the chart and the actual size of the feature on the Earth’s surface.
How does a chart’s scale appear?
One of two ways; ratio or fraction
What does a small scale chart cover?
A large area
What does a large scale chart cover?
A small area
What scale does a harbor chart have?
Scales larger than 1:50,000. Harbor charts are used in harbors, anchorage areas and smaller waterways.
What is the scale for coastal charts?
1:50,000 - 1:150,000 Coastal charts are for coastal navigation, outside reefs and shoals when the vessel is in sight of land or aids to navigation.
What is the scale for sailing charts?
1:600,000 or smaller and are used in fixing a ship’s position as it approaches the coast from open ocean