TOPIC 1 Flashcards
the extension of lines or planes to intersect a given surface; the transfer of a point from one surface to a corresponding position on another surface by graphical or analytical means.
Projection
a systematic drawing of lines on a plane surface to represent the parallels of latitude ant the meridians of longitude of the Earth or a section of the Earth. A map projection may be established by analytical computation or may be constructed geometrically.
Map Projection
meeting a curve or surface in a single point if a sufficiently small interval is considered.
Tangent
a surface of such nature that a strait line joining 2 of its points lies wholly in the surface (a flat surface).
Plane
A cylinder is placed around the Earth and is tangent to the equator The planes of the meridians are extended & they intersect the cylinder in a number of vertical lines.
Cylindrical Projection
Most common projection used for navigation is the ____________ which is classified as a Cylindrical Projection.
Mercator Projection
The length of a meridian, expressed in minutes of arc at the equator as a unit, constitutes the number of Meridional Parts corresponding to that latitude. (Used to make Mercator Projections & Mercator Sailings.)
Meridional Parts
These are drawn Straight
Rhumb Lines
are arcs the curve toward the nearest pole.
Great Circles
You can use the Latitude Scale to measure distance
True
A plane is placed tangent to the surface of the Earth. The points are projected from the center of the Earth to the plane.
Gnomonic Chart Projection
how the Earth looks from a certain point of view & is projected onto a plane to create an image on the chart.
The projection is perspective
A tangent plane is placed on the Earth. This projection is perspective from the center of the Earth. Basically, if you take a flashlight at the center of the Earth & shine it in the direction of the tangent plane, the land features will be the shadows that shine on the tangent plane.
Oblique Gnomonic
This chart is often called a “______” Chart because its only use is to Plan Great Circle Voyages. Points along the track then get transferred to a Mercator Projection.
Great Circle
A great circle is not conformal or _______
Orthomorphic
plot as straight lines and rhumb lines plot as curves away from the pole.
Great Circles
will appear as straight lines that converge at the poles as they do on the Earth.
The Meridian
The_______except the equator, will be curved.
Latitude Lines
Charts will provide more information on “____”
Zone of confidence
The Nautical Charts showing the Earth’s surface or a portion thereof on a plan, in a certain proportion (scale) and with deformations subject to mathematical laws.
Such a chart must meet the following conditions:
- The quick and easy insertion of the geographical coordinates of a point;
- The angles on the chart to be equal to those on the surface of the Earth;
- The rhumb line and the great circle can be drawn by a straight line.
On a chart are shown a lot of elements using abbreviations, symbols, explanatory notes, warnings, namely:
a. The coast line;
b. The seabed topography;
c. The nature of the seabed;
d. Dangers for navigation;
e. Navigation aids;
f. Natural and artificial navigation landmarks;
g. The magnetic declination and magnetic anomalies;
h. The elements of the tide and currents;
i. Places for anchorage;
j. The boundaries of the different regions;
k. Fairway.
– Drawn at a scale between 1: 500,000 – 1: 5,000,000
– Are represented large oceanic basins and are used for:
· Study of the navigation conditions;
· Preparing the sea passage;
General Charts
– Drawn at a scale between 1: 100,000 – 1: 500,000
– Used for navigation at deep sea or near the coasts;
– On which are represented the most important elements for navigation;
Route Charts
– Drawn at a scale between 1: 50,000 – 1: 75,000;
– Used for navigation close to land, among islands, fjords, straits;
Coast Charts
– Drawn at a scale between 1: 5,000 – 1: 25,000;
– Used for operating in ports, roads, gulfs and bays.
For navigation purposes are used the following cartographic projections:
Harbor Charts
– With Rectangular Canvas;
– And the rhumb line appears as a straight line;
Mercator’s Projection
– Used for the navigation on the great circle;
Gnomonic Projection
– Used for navigation in the polar regions.
Stereo geographic Projection
Scales are expressed as ratios and differ from map to map. The scale, printed in the upper right corner of the map, will look something like 1:100,000. A ratio of 1:10,000 indicates that every 1in (2.5cm) the map equals 10,000in (25,000cm) in the real world.
1 Use the scale indicator to track distance on a chart.
Rky Stands for?
Rocky Floor
Tr indicates?
Nearby Tower
Whf stands for?
Wharf
Bn means?
Beacon
CG may indicate?
Coast Guard station on a U.S. map
A nautical chart presents most of the information used by the marine navigator, including
latitude and longitude scales, topographical features, navigation aids such as lighthouses and radio beacons, magnetic information, indications of reefs and shoals, water depth, and warning notices.
