![]() ![]() This enabled mariners to navigate safely far from land, increasing sea trade, and contributing to the Age of Discovery. The invention of the compass made it possible to determine a heading when the sky was overcast or foggy, and when landmarks were not in sight. ![]() On cloudy days, the Vikings may have used cordierite or some other birefringent crystal to determine the sun's direction and elevation from the polarization of daylight their astronomical knowledge was sufficient to let them use this information to determine their proper heading. The Norse are believed to have used a type of sun compass to locate true north. Objects that have been understood as having been used for navigation by measuring the angles between celestial objects, were discovered in the Indus Valley site of Lothal. Other techniques included sampling mud from the seafloor (China), analyzing the flight path of birds, and observing wind, sea debris, and sea state (Polynesia and elsewhere). Navigation prior to the compass īefore the introduction of the compass, geographical position and direction at sea were primarily determined by the sighting of landmarks, supplemented with the observation of the position of celestial bodies. This was replaced in the early 20th century by the liquid-filled magnetic compass. Dry compasses begin appearing around 1269 in Medieval Europe and 1300 in the Medieval Islamic world. The first usage of a compass in Western Europe was recorded in around 1190 and in the Islamic world 1232. Magnetized needles and compasses were first described in medieval Europe by the English theologian Alexander Neckam (1157–1217 AD). Later compasses were made of iron needles, magnetized by striking them with a lodestone. Shen Kuo provided the first explicit description of a magnetized needle in 1088 and Zhu Yu mentioned its use in maritime navigation in the text Pingzhou Table Talks, dated 1111–1117. It was called the "South Pointing Fish" and was used for land navigation by the mid-11th century during the Song dynasty (960–1279 AD). The first compasses were made of lodestone, a naturally magnetized stone of iron, in Han dynasty China. The history of the compass started more than 2000 years ago during the Han dynasty (202 BC – 220 AD). North corresponds to 0°, so east is 90°, south is 180° and west is 270°. The angle increases in the clockwise position. The structure of a compass consists of the compass rose, which displays the four main directions on it: East (E), South (S), West (W) and North (N). The compass is a magnetometer used for navigation and orientation that shows direction in regards to the geographic cardinal points. Finally, use the bottom edge of the protractor as a straight edge to draw a line between the two points.Song dynasty figurine of a man holding a compass ![]() Rotate the protractor and line the bottom edge up between the vertex and the small dot. Now, find the hash mark on the protractor that corresponds with the angle you want to draw, and draw a small dot outside of it. Then, line the bottom edge of the protractor up with the vertex and draw a straight line along it. Draw a small dot in the hole on the protractor to mark the vertex. To draw an angle with a protractor, first place the center point along the bottom edge of the protractor where you want the vertex of the angle to be. If the angle is facing left, use the top row of numbers. If the angle is facing to the right, use the bottom row of numbers on the protractor. Follow the other leg of the angle up to the protractor’s arc to see what number it intersects with and find the degree of the angle. Line up the bottom edge of the protractor with one leg of the angle. To measure angles with a protractor, first place the center point along the bottom edge of the protractor over the vertex of the angle you're measuring. You can use a protractor to measure and draw angles. ![]()
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