Topographic Maps from history to knowledge

Topographic maps  

 

Topographic Machine (Lieca TS06)

Every map has its own special language. The road maps have lines for streets, routes, and highways. The political maps have boundary lines, capital stars, and major cities. For topography maps, the contour lines are the key to understanding this map's special language. Topography is the size and shape of natural and human-made land features. Map projections and globes do not give scientists detailed information about our planet's surface. This is why topographic maps are very useful. 

 Earth scientists, such as geographers and cartographers, want to know about the Earth's surface. They want to know about the shape, size, and elevation of its land features. Elevation is the height of a land feature above sea level. This is also referred to as the mean sea level. Elevation is calculated by choosing a point halfway between the highest and lowest ocean tide levels. At mean sea level the elevation of a land feature is zero. 

 Contour lines show changes in elevation. They are isograms because they connect points on the land surface that have the same elevation. These lines also show the shape of the land feature. Every fifth contour line is bolder than the other lines. This line is an index contour. Cartographers include the index contour to make the map easier to read. (This way you don't have a bunch of squiggly lines going on forever in front of your eyes.) The four lines above and below the index contour are not in bold. Index contours are also labeled with the elevation of that area. Contour lines also never cross. If an exact elevation is available, an "X" will be added next to the number. If the contour lines are spaced widely apart, this means the elevation is increasing gradually. The land in that area is basically level. Contour lines that are drawn close together mean a sharp increase in elevation. They are used to show the slope or steepness of a land feature.


The Datum