What is Thematic Mapping

Thematic Maps serve an important source of GIS information. A thematic map is a map used to convey geographical information such as climate, density of population, land use and other geographical aspects of any city, region, state or country. Thematic maps also known as geographic assays use/utilize base data of places and coastlines as a reference point and then draw out the inferences.

Thematic maps are used not only for showing the distribution of different attributes but they also depict relationship between different attributes also. Similar to dynamic mapping, thematic mapping enables a geographer to update/change mapping elements and view the changes as they happen. Thematic maps are very useful because they provide information about locations, outline the relationships between different attributes and the charts made can be used for navigational purpose as well.

The origin of thematic maps can be traced back to 1686, when Edmond Halley (an English astronomer) published a map known as terrestrial map. This map can be called as the earliest map that came into existence. However, the obvious use of thematic mapping first came out in 1854, when John Snow, a physician from London utilized thematic principles for devising a map for analyzing the spread of cholera in a particular area. Since then, these thematic maps have been used regularly for getting information about a particular area.

While making a map, the cartographer needs to be careful of portraying the data on the map in such a manner that the audience can understand it very carefully. The cartographer needs to examine the location or the physical area and thereafter collect the data sets. Although the general principle remains the same but there are different techniques for mapping a particular area. Choropleth is the most frequently used method for thematic mapping. In case of Proportional symbols the area or the information is represented with the help of point locations.

In Isarithmic method, the maps are used for depicting smooth continuous phenomena such as precipitation etc. In the Dot method, a particular feature or occurrence is used for displaying a spatial pattern. Dasymetric maps make use of areal symbols. However, although boundaries are displayed on dasymetric maps, these geographic units may span multiple theme values. This method is used quite rarely.

So, I hope that you can see the importance of thematic maps pertaining to the information they convey. Thematic maps are an important tool for getting all kinds of information regarding geographical regions.