In order to accurately display the position of every place on the earth, people assume a coordinate system for the earth's surface, that is, latitude and longitude lines. So, how did the original longitude and latitude lines form? How to measure? In 344 AD, Alexander crossed the sea and invaded, then moved eastward. Military geographer Nierkus searched for information along the way and prepared to draw a "map of the world". He found that on the route of Alexander's eastward expedition, from west to east, the change of seasons was similar to the length of sunshine. So he made an important contribution-for the first time, he drew a parallel line on the earth, starting from the Strait of Gibraltar, along the torus and Himalayas, and reaching the Pacific Ocean.

Alexander's empire was a flash in the pan and soon collapsed. But in Alexandria, Egypt, a famous library appeared. Eratosthenes, a curator for many years, is well-read and proficient in mathematics, astronomy and geography. He calculated that the circumference of the earth was 46,250 kilometers and drew a map of the world with 7 meridians and 6 latitudes.

In 120, a young man also studied astronomy and geography in this ancient library. This is Claudius Ptolemy. Ptolemy integrated the previous research results, thought that maps should be drawn according to fixed points with known latitude and longitude, and put forward the concept of drawing latitude and longitude network on maps. To this end, Ptolemy measured the latitude and longitude of important cities and strongholds in the Mediterranean and compiled eight volumes of geographical works. Including the latitude and longitude of 8000 places. In order to draw the longitude and latitude lines on the earth on a plane, he tried to draw them into simple sectors, thus drawing the famous Ptolemy map. /kloc-At the beginning of the 5th century, the navigator Henry began to put "Ptolemy Map" into practice. However, after repeated inspection, I found that this map is not practical. Some of Henry's captains said with regret, "Although we admire the famous Ptolemy very much, we found that the fact is contrary to what he said."

A "standard clock" is the key to correctly determine the latitude and longitude. It is obviously more convenient and practical to make accurate clocks and watches at sea than to rely on celestial bodies to time. /kloc-the progress of mechanical technology in the 0/8th century has finally created conditions for solving this long-standing problem. Harrison, a watchmaker in Yorkshire, England, spent 42 years making five timepieces in succession, each of which is more accurate and perfect than the other, and the accuracy is getting higher and higher. The fifth stop is only the size of a pocket watch, and the error caused by longitude measurement is only 1/3 miles. Almost at the same time, a sea timepiece designed and manufactured by French watchmaker Pierre leroy was put into use. At this point, the problem of longitude measurement at sea has finally been initially solved.

Latitude and longitude calculation method

The coordinate points of longitude and latitude lines can determine any position on the map, and you can know your corresponding position on the map by mastering the longitude and latitude lines and determining methods.

Meridian refers to the meridian that passes through the north and south poles and divides the circumference of the earth into 360 degrees. You can calculate the longitude of your position by time. For example, when Greenwich Mean Time is zero, your local time is exactly 8: 20 and the time difference between the two places is 8 hours and 20 minutes. So the longitude of your location is 15× 8+20 ÷ 4 = 125, which means east longitude 125 degrees, which is the ordinate on the map. On a long-distance trip, tourists can calculate the longitude of this place as long as they bring two watches, one is Greenwich Mean Time and the other is local time.

Latitude is a coordinate line parallel to the equator, which divides the northern and southern hemispheres into 90 degrees and intersects the meridian vertically. Latitude 1 spans about 1 10 km. The method of determining latitude is simple. On the night when you can see Polaris, you only need to measure the angle between a horizontal line and Polaris with a protractor. This degree is latitude.

Mastering the measurement method of latitude and longitude is the most basic skill for a tourist. This skill is the most important positioning method in wilderness, Gobi, desert and ocean.