Thematic Mapping – Geography Notes – For W.B.C.S. Examination.

থিম্যাটিক ম্যাপিং – ভূগোল নোট – WBCS পরীক্ষা।

A thematic map is a map that focuses on a specific theme or subject area such as physical phenomena like temperature variation, rainfall distribution and population density in an area. Thematic maps emphasize spatial variation of human issues like population density or prevalence of diseases. This is in contrast to general reference maps, which just show natural features like landforms, lines of transportation, rivers, human settlements and political and administrative boundaries. Thematic maps use the base data of general reference maps as reference points for mapping specific themes, and to enhance the understanding of the map’s theme and purpose. Normally, however, all thematic maps use maps with coastlines, city locations and political boundaries as their base maps.Continue Reading Thematic Mapping – Geography Notes – For W.B.C.S. Examination.

The map’s specific theme is then layered onto this base map via different mapping programs and technologies like a geographic information system (GIS). Thematic maps did not develop as a map type until the mid-17^th Century because accurate base maps were not present prior to this time. The first thematic maps were created only after accurate base maps displaying coastlines, cities and other boundaries became available.

While general reference maps show where something is in space, thematic maps tell a story about that place, for example, A city map. Thematic maps are sometimes referred to as graphic essays that portray spatial variations and interrelationships of geographical distributions. Location, of course, is important to provide a reference base of where selected phenomena are occurring.

Mapping Considerations:

There are several things to consider while designing thematic maps. The most significant consideration ought to be the users, since this helps to decide as to which reference points need to be included in addition to the theme. For example, a thematic map intended for use by political scientists may include political boundaries, while one intended for a geologist might need contours showing elevation. The sources of a thematic map’s data are also important and should be carefully considered. In order to make the most useful maps, one must find accurate, current and reliable sources of information on a wide range of subjects – from environmental features to demographic data.

Types of Thematic Maps:

There are three categories of thematic maps – univariate, bivariate and multivariate. A thematic map is univariate if the non-location data is all of the same kind. Population density, cancer rates, and annual rainfall are three examples of univariate data. Bivariate mapping shows the geographical distribution of two distinct sets of data. For example, a map showing both rainfall and elevation may be used to explore a possible correlation between the two variables. More than two sets of data leads to multivariate mapping. For example, a single map might show rainfall in addition to elevation and vegetation density in order to understand their interrelationships.

Choropleth Maps:

 A choropleth map is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per-capita income. This technique assumes a relatively even distribution of the measured phenomenon within each region. Generally speaking, differences in hue are used to indicate qualitative differences, such as land use, while differences in saturation or lightness are used to indicate quantitative differences, such as population.

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