The contour lines that are far apart are gradual slopes; the contour lines that are close together are steep. If you are navigating, it is easier to walk on the shallower slope. Other features such as saddles the place between two peaks are generally also easier to navigate.
Related questions How do contour lines show hills and depressions? Why do contour lines never cross on a topographic map? How do you recognize a valley on a topographic map?
How can you identify a steep area on a topographic map? How do you make a profile of a landform on a topographic map? What information can be found in the map key? Why do people use topographic maps? How do you read a topographic map? Where these lines are above sea level they are simply called contour lines and where they are below sea level they are called bathymetric contour lines. Contour lines can tell an informed reader many things about the shape of the land and its ruggedness.
The closer contours are together the steeper the land and the further they are away from each other the flatter the land. On the Nullarbor Plain, for instance, very few contour lines would be shown, but over the Snowy Mountains an enormous number of contour lines would be shown. A word of warning: topographic maps do not show every contour line, rather they choose sample of the lines. For example every 20, 50, metres — depending on the scale of the map. This is called the contour interval of the map.
As a result of this selection process, the difference in density of the contour lines is only indicating relative changes in the shape of the landscape — on that map! The reading of topographic maps and interpretation of contour lines, is a much written about topic. Please refer to the Further Reading hyperlinks to learn more about contours and understanding what they mean. A bit of history: Contours were developed in the 19th century s.
Prior to this, various systems of drawing the relief had been experimented with, including a system called hachuring.
These systems have largely disappeared from modern map making, but they are intriguing to read about. By comparing these two it is clear that the map is an excellent summary of the landscape of the area. Note that the features which dominate the photograph also dominate the map. Four maps have been selected across Australia to illustrate the vast range of information which can be contained in a topographic map. These maps are all part of a series of maps which cover the whole of Australia and they have been produced using the same specification — i.
For series maps, particularly topographic series maps , a variety of map conventions have been developed. One which can be confusing is the different map numbering systems. In series maps it is essential that individual maps should be easily and uniquely identifiable. Map name alone is not sufficient to easily identify and locate an individual map. This is especially a problem where there are a large number of maps in a topographic map series.
For example in Australia there are:. This system hinged on two features:. It was agreed that the smaller scale grid should be for ,, often called million scale topographic mapping.
The 'nested' smaller scales were ,, ,, ,, , etc. In the Fifth International Geographical Congress agreed on the development of a world-wide, ,, or million scale series of maps. The maps were to be produced using an internationally agreed, consistent specification. For several reasons the development of the IMW maps was slow — reasons included two World Wars, the Great Depression and lack of funding in poorer countries.
International interest waned and by the s only of the proposed maps were completed. The project was abandoned by the mids. The Australian component of the IMW was 49 maps. Work on these began in and was completed in Whatever shape the contour line makes is the same shape that the land forms in that particular area. Contour lines that seem close together normally indicate steep land, while the lines that are spread further apart show land that is relatively flat.
Contour lines that tell you there are two peaks indicate the presence of a saddle, or gap, betwixt the peaks. To match a topographic map to the landscape around you, which helps to identify features like mountains and creek beds, make sure the map is oriented correctly.
Line up the compass needle, which points north, with the arrow on the compass rose to accomplish proper orientation.
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