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制图学

在地图或航图上用图形表示地球自然面貌的科学和技术。它是一门古老的学科,可上溯到史前时代人们所画的渔猎地区图。巴比伦人把世界画成平的圆盘状,托勒密於2世纪着有地理学八卷集,指出地球是一个圆球,为後人研究奠定了基础。中世纪时,按照托勒密的理论绘制的地图都以耶路撒冷为中心,并把东方画在图的上方。较精确的地图是从14世纪开始的,当时为了航海制成了航图。新大陆发现後,要求制图学采用新技术,特别是采用正确的投影技术。麦卡托使用一种圆柱投影方式,视地球为一圆柱。圆柱投影法具有许多优点,但在高纬度地区常常失真。等高线地图是用线连接同等高度的点来显示地形,以平均海平面来做参考点。现代制图方法大多使用航空照相或卫星雷达作为绘制任何一种地图或航图的基础,用这种方法作出的地球地形图达到前所未有的准确度。透过人造卫星摄影,现已能够绘制月球以及一些行星和它们的卫星的表面图。

cartography

Art and science of representing a geographic area graphically, usually by means of a map or chart. Political, cultural, or other nongeographic features may be superimposed. Ptolemy's eight-volume Geography showed a spherical earth. Medieval European maps followed Ptolemy's guide but placed east at the top of the map. The 14th century saw the development of more accurate maps for use in navigation. The first surviving globe dates from 1492. Discovery of the New World led to new techniques in cartography, notably projection of a curved surface onto a flat surface. Gerardus Mercator used a cylindrical projection; which treats the earth as a cylinder. Cylindrical projections have many advantages, though they cause distortions at high latitudes. Contour maps show relief by connecting points of equal elevation with lines, mean sea level being the reference point. Modern cartography uses aerial photography and satellite radar for a degree of accuracy previously unattainable. Satellites have also made possible the mapping of features of the moon and of several planets and their moons. See also geographic information system, global positioning system.