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Loxodromic Navigation
Loxodromic navigation (from Greek ''λοξóς'', oblique, and ''δρóμος'', path) is a method of navigation by following a rhumb line, a curve on the surface of the Earth that follows the same angle at the intersection with each meridian. This serves to maintain a steady course in sailing. Navigating on a spherical surface with a fixed course (\beta in the figure) results in a spiral path that approaches the North Pole for courses ranging from 270º to 090º and the South Pole for courses from 090º to 270º. On a nautical chart plotted according to the Mercator projection, a loxodromic course appears as a straight line. Comparison Chart See also * Great circle navigation * Windrose network * Map * Portolan map * Marine sandglass * Compass rose * Isoazimuthal The isoazimuth is the locus of the points on the Earth's surface whose initial orthodromic course with respect to a fixed point is constant. That is, if the initial orthodromic course Z from the starting poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loxodrome
In navigation, a rhumb line, rhumb (), or loxodrome is an arc (geometry), arc crossing all meridian (geography), meridians of longitude at the same angle, that is, a path with constant bearing (navigation), bearing as measured relative to true north. Introduction The effect of following a rhumb line course on the surface of a globe was first discussed by the Portuguese people, Portuguese mathematician Pedro Nunes in 1537, in his ''Treatise in Defense of the Marine Chart'', with further mathematical development by Thomas Harriot in the 1590s. A rhumb line can be contrasted with a great circle, which is the path of shortest distance between two points on the surface of a sphere. On a great circle, the bearing to the destination point does not remain constant. If one were to drive a car along a great circle one would hold the steering wheel fixed, but to follow a rhumb line one would have to turn the wheel, turning it more sharply as the poles are approached. In other words, a g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthodromic Vs Loxodromic
An orthodromic impulse runs along an axon in its anterograde direction, away from the soma. In the heart, orthodromic may also refer to an impulse going in the correct direction from the dendrites to axon terminal (from the atria to the ventricles) in contrast to some impulses in re-entry. See also *Antidromic *Action potential *Anterograde Tracing In neuroscience, anterograde tracing is a research method which is used to trace axonal projections from their source (the cell body or soma) to their point of termination (the synapse). A hallmark of anterograde tracing is the labeling of the pres ... References Neurophysiology {{Neuroscience-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoazimuthal
The isoazimuth is the locus of the points on the Earth's surface whose initial orthodromic course with respect to a fixed point is constant. That is, if the initial orthodromic course Z from the starting point ''S'' to the fixed point ''X'' is 80 degrees, the associated isoazimuth is formed by all points whose initial orthodromic course with respect to point ''X'' is 80° (with respect to true north). The isoazimuth is written using the notation ''isoz(X, Z)'' . The isoazimuth is of use when navigating with respect to an object of known location, such as a radio beacon. A straight line called the ''azimuth line of position'' is drawn on a map, and on most common map projections this is a close enough approximation to the isoazimuth. On the Littrow projection, the correspondence is exact. This line is then crossed with an astronomical observation called a Sumner line, and the result gives an estimate of the navigator's position. Isoazimutal on the spherical Earth Let ''X' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compass Rose
A compass rose, sometimes called a wind rose, rose of the winds or compass star, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions (north, east, south, and west) and their intermediate points. It is also the term for the graduated markings found on the traditional magnetic compass. Today, a form of compass rose is found on, or featured in, almost all navigation systems, including nautical charts, non-directional beacons (NDB), VHF omnidirectional range (VOR) systems, global-positioning systems (GPS), and similar equipment. Types Linguistic anthropological studies have shown that most human communities have four points of cardinal direction. The names given to these directions are usually derived from either locally-specific geographic features (e.g. "towards the hills", "towards the sea") or from celestial bodies (especially the sun) or from atmospheric features (winds, temperature). Most mobile populations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Sandglass
A marine sandglass is a timepiece of simple design that is a relative of the common hourglass, a marine (nautical) instrument known since the 14th century (although reasonably presumed to be of very ancient use and origin). Sandglasses were used to measure the time at sea or on a given navigational course, in repeated measures of small time increments (e.g., 30 minutes). Used together with the chip log, smaller marine sandglasses were also used to measure the boat speed through the water in knots. Although vital to maritime navigation, marine sandglasses were not accurate measuring instruments for the passage of time; many design and environmental factors could affect the duration of sand's flow, and therefore its reported time. Their use continued through the early 19th century, when they were supplanted by reliable mechanical timepieces, and by other advances in marine navigation. Marine sandglasses were very popular on board ships, as they were the most dependable measurement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portolan Map
Portolan charts are nautical charts, first made in the 13th century in the Mediterranean Sea, Mediterranean basin and later expanded to include other regions. The word ''portolan'' comes from the Italian language, Italian ''portulano'', meaning "related to ports or harbours, harbors", and which since at least the 17th century designates "a collection of sailing directions". Definition The term “portolan chart” was coined in the 1890s because at the time it was assumed that these maps were related to portolani, medieval or early modern books of sailing directions. Other names that have been proposed include rhumb line charts, compass charts or loxodromic navigation, loxodromic charts whereas modern French scholars prefer to call them nautical charts to avoid any relationship with portolani. Several definitions of portolan chart coexist in the literature. A narrow definition includes only medieval or, at the latest, early modern Nautical chart, sea charts (i.e. maps that prim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Windrose Network
A rhumbline network (or windrose network) is a navigational aid consisting in multiple lines in a web-like grid drawn on portolan charts (and other early maps). These nautical charts were used in the medieval age and age of exploration in marine navigation. Since the invention of the Mercator projection c. 1600, the term ''rhumb line'' (or ''loxodrome'') has been redefined to mean a mathematically precise curve of constant bearing on the Earth's surface. To avoid confusion, the lines on earlier sailing charts can be unambiguously called ''windrose lines'', since they are not true rhumb lines by the modern definition. A rhumb line in the modern sense is only straight on a chart drawn with the Mercator projection, but not on charts from the 13th–16th centuries. Older windrose lines were a close approximation on charts of the Mediterranean Sea and surrounding areas, but the rhumb lines on small-scale maps such as the Teixeira planisphere were highly inaccurate. The grid can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Circle Navigation
Great-circle navigation or orthodromic navigation (related to orthodromic course; from the Greek ''ορθóς'', right angle, and ''δρóμος'', path) is the practice of navigating a vessel (a ship or aircraft) along a great circle. Such routes yield the shortest distance between two points on the globe. Course The great circle path may be found using spherical trigonometry; this is the spherical version of the '' inverse geodetic problem''. If a navigator begins at ''P''1 = (φ1,λ1) and plans to travel the great circle to a point at point ''P''2 = (φ2,λ2) (see Fig. 1, φ is the latitude, positive northward, and λ is the longitude, positive eastward), the initial and final courses α1 and α2 are given by formulas for solving a spherical triangle :\begin \tan\alpha_1&=\frac,\\ \tan\alpha_2&=\frac,\\ \end where λ12 = λ2 − λ1In the article on great-circle distances, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercator Projection
The Mercator projection () is a cylindrical map projection presented by Flemish geographer and cartographer Gerardus Mercator in 1569. It became the standard map projection for navigation because it is unique in representing north as up and south as down everywhere while preserving local directions and shapes. The map is thereby conformal. As a side effect, the Mercator projection inflates the size of objects away from the equator. This inflation is very small near the equator but accelerates with increasing latitude to become infinite at the poles. As a result, landmasses such as Greenland, Antarctica and Russia appear far larger than they actually are relative to landmasses near the equator, such as Central Africa. History There is some controversy over the origins of the Mercator. German polymath Erhard Etzlaub engraved miniature "compass maps" (about 10×8 cm) of Europe and parts of Africa that spanned latitudes 0°–67° to allow adjustment of his portable pocket-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greek Language
Greek ( el, label=Modern Greek, Ελληνικά, Elliniká, ; grc, Ἑλληνική, Hellēnikḗ) is an independent branch of the Indo-European family of languages, native to Greece, Cyprus, southern Italy (Calabria and Salento), southern Albania, and other regions of the Balkans, the Black Sea coast, Asia Minor, and the Eastern Mediterranean. It has the longest documented history of any Indo-European language, spanning at least 3,400 years of written records. Its writing system is the Greek alphabet, which has been used for approximately 2,800 years; previously, Greek was recorded in writing systems such as Linear B and the Cypriot syllabary. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems. The Greek language holds a very important place in the history of the Western world. Beginning with the epics of Homer, ancient Greek literature includes many works of lasting impo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautical Chart
A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land (topographic map), natural features of the seabed, details of the coastline, navigational hazards, locations of natural and human-made aids to navigation, information on tides and currents, local details of the Earth's magnetic field, and human-made structures such as harbours, buildings, and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper (raster navigational charts) or computerized electronic navigational charts. Recent technologies have made available paper charts which are printed "on demand" with cartographic data that has been downloaded to the commercial printing company as recently as the night before printing. With each daily download, critica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Pole
The South Pole, also known as the Geographic South Pole, Terrestrial South Pole or 90th Parallel South, is one of the two points where Earth's axis of rotation intersects its surface. It is the southernmost point on Earth and lies antipodally on the opposite side of Earth from the North Pole, at a distance of 12,430 miles (20,004 km) in all directions. Situated on the continent of Antarctica, it is the site of the United States Amundsen–Scott South Pole Station, which was established in 1956 and has been permanently staffed since that year. The Geographic South Pole is distinct from the South Magnetic Pole, the position of which is defined based on Earth's magnetic field. The South Pole is at the centre of the Southern Hemisphere. Geography For most purposes, the Geographic South Pole is defined as the southern point of the two points where Earth's axis of rotation intersects its surface (the other being the Geographic North Pole). However, Earth's axis of rotat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
