Chorographic Chart
Delineates a particular country.
Coast Survey Chart. Delineations of the coast as issued by the United States Coast Survey Office at Washington.
General Chart. A map on a small scale, covering a large extent of coast line and ocean.
Great Circle Charts. Special charts constructed on the central or gnomonic projection, in which all great circles are represented as straight lines. These answer the same purpose for great circle sailing that Mercator's chart answers for rhumb sailing.
Harbor Chart. Also known as a Harbor Plan. A map of a particular harbor, on a large scale, for the convenience of seamen, giving the lights, buoys, soundings, courses, leading marks, etc. The parallels and meridians are, as a rule, not shown.
Heliographic Chart. A chart representing the sun, and the spots on his surface.
Hydrographic Charts. Charts published by the Hydrographic Office in Washington, which office is under the jurisdiction of the Bureau of Navigation. These charts delineate the navigable waters of the world, land, rocks, shoals, depths, currents, tides, latitudes, longitudes, etc.
Magnetic Chart. (See Variation Chart.)
Mercator's Chart. A style of chart invented by Gerard Kauffman, better known as Mercator, on which the parallels and meridians are all straight parallel lines, but only the meridians are equi-distant; the distance between the parallels increases from the equator toward either pole in the same proportion as the degrees of longitude decrease on the globe, this projection being constructed by the aid of the table of meridional parts.
Ocean Charts. Maps representing the entire area of one of the five oceans of the world--Atlantic, Pacific, Indian, Arctic and Antarctic.
Z. Zenith
ABC. Vertical section of the earth
AE. Height of observers' eye above earth's surface.
FEG. Parallel to the tangent to the surface at A, representing the true horizon.
EIH. Represents the apparent horizon
FEH. Dip of the horizon
M. Object to be observed by throwing image to apparent horizon at H
MEH. Observed altitude, which is greater than the angle MEF by the quantity of the angle FEH
ABC, DEF. Atmosphere surrounding the earth
D. Observer
a. Star
Da. The line the star would be observed on if there was no refraction
Db. The line the star is observed on owing to refraction.
SECOND CONSIDERATION
T. Sun below the horizon.
TI. A ray of light proceeding from T, comes in a right line to I, and is there turned out of its rectilinear course, and is so bent down towards the eye of the observer at D that the sun appears in the direction of the refracted ray above H.
When a body is in the zenith there is no refraction, the rays of light entering the atmosphere in straight lines.
Physical Charts. Maps delineating the currents and drifts of the ocean, prevailing winds, ice limits, etc.
Plane Chart. A map representing the meridians as parallel, and on which no allowance is made for the spherical figure of the earth.
Polar Charts. Maps of the regions about the poles of the earth.
Selenographic Chart. A chart representing the moon, and the spots on her surface.
Skeleton Chart. Also known as a Track Chart. Blank sheets on Mercator's projection for plotting the track of a vessel.
Telegraphic Chart. A chart on which the line of a telegraph-cable is shown.
Topographic Chart. A delineation of an area of country.
Track Chart. (See Skeleton Chart.)
True Chart. A map representing geographical bearings and directions without reference to the variation of the compass.
Variation Chart. A chart on Mercator's projection representing the variation of the compass by curved lines. Variation Charts of the World may be obtained from any nautical dealer.