The earliest known map was painted on the walls of a cave in Lascaux, France about 17,000 years ago. It was a star chart, with dots depicting Vega, Deneb, and Altair (the Summer Triangle) as well as the Pleiades star cluster. The oldest map of land is a small clay tablet, estimated to be 4500 years old, found near Kirkut Iraq. The Babylonians used accurate surveying techniques and this map (with cardinal directions) shows a river valley which includes a plot of land described as 354 iku (12 hectares) owned by a person called Azala.
The oldest surviving Chinese maps date from 2400 years ago.
Several Greek philosophers claimed Earth was a sphere but Aristotle (384–322 BCE) is credited with the proof. He pointed out that lunar eclipses were always circular, some stars were not visible everywhere and ships crossing the horizon seemed to sink from view.
Eratosthenes (275–195 BCE) coined the term, "geography", and was the first person to determine the Earth's circumference (to within 1.4 % accuracy!). He learned of a well in the Egyptian city of Swenett (modern Aswan) into which the sun shone directly only on the summer solstice. On that day, he comparing the length of shadows in Alexandria, 524 miles (843 km) farther North. He assumed the Earth to be a sphere and calculated that the circumference to be 250,000 stadia or 39,375 km, (which is 1.4% less than the correct number of 40,076 km or 24902 mile or 2160 nautical mile).
He went on to create charts with meridians (north-south lines) and parallels (west–east lines) with their origin in the Greek city of Rhodes. These axis lines were placed over the map of the earth and divided the world into sectors.
Claudius Ptolemy (90–168 CE) revolutionized map making by using perspective projection to depict the spherical earth on a map and suggesting precise methods for fixing the position of geographic features on its surface using astronomy and mathematics with a coordinate system of parallels of latitude and meridians of longitude.
Gerardus Mercator of Belgium published an early map of the world in 1569 CE based on a projection that was far more accurate than earlier maps. The Mercator projection, a cylindrical map projection, is uniquely suited to marine navigation as all lines of constant bearing (those making constant angles with the meridians - rhumb lines - the shortest line on a sphere ) are represented by straight segments on a Mercator chart. Courses and bearings are measured with protractors and easily transferred from point to point, on the chart, with the help of parallel rulers. Dividers are used to mark distances from the minutes of arc scale marked on the vertical axis (meridian angles) which are nautical miles.
A meridian (line of longitude) is the half of a great circle on the Earth's surface, between the North Pole and the South Pole. (It is thus 10800 nautical miles long so that one degree of longitude corresponds to 60 nautical miles and one arc-minute equals one nautical mile.) This distance is equal to 20,003.93 km or 12,429.9 statute miles. The prime (or zero) meridian passes through Greenwich observatory in Britain and all others are measured in degrees East or West of Greenwich up to 180 degrees west (or 180 degrees east).
On small maps errors are negligible but large maps distorts the size of objects as the latitude increases from the Equator. So landmasses near the poles, like Greenland and Antarctica, appear much larger than they actually are. The distance between two points in Euclidean space is the length of a straight line between them, but on a sphere there are no straight lines. The shortest distance between two points on the surface of a sphere is known as a rhumb line or great-circle or orthodromic distance.
Early sailors preferred to sail along a line of latitude as the angle between the horizon and the pole star was always the same, but this was not the shortest distance and over a long voyage the difference could be significant. Navigators began to calculate the course change required as they crossed each 15 degree meridian line. Initially the course would be greater (or less) than the rhumb line (the course line on a Mercator chart) and it would become less (or greater) that the rhumb line half way through the voyage.
A latitude is a line parallel to the equator measured in degrees ranging from 0° at the Equator to 90° (North or South) at the poles. Note that one degree of Latitude is one nautical mile only at the equator. At any other latitude it will be less, and at the poles it is zero.
So any point on the Earth's surface can be identified by its latitude and longitude. For example New York City is at 40.7128° N, 74.0060° W. Which means it is 40.7128° North of the equator and 74.0060° West of Greenwich in Britain. Traditionally 40.7128° N, 74.0060° W would be written as 40° 42.8' (arc-minutes)N and 74° 0.4' W. So, 40° x 60 = 2400 n.miles + 42.8 n.miles = 2442.8 nautical miles north of the equator.
Sidney Australia is at 33.8688° S, 151.2093° E. (South of the equator and east of Greenwich).
London, Britain, is at 51.5074° N, 0.1278° W (it is just west of Greenwich and 3090.444 n.miles north of the equator.
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Middle Era
Não FicçãoJesus and Muhammad adopted the Hebrew's belief in one God and Christianity and Islam spread throughout the world. The Chinese were using gunpowder in the 9th century and, by the 13th , cannon dominated the battlefields. Paper money appeared in China...
