Dasymetric map
Topic: Graphical Representation of Data and Thematic Maps · NCERT: Beyond NCERT
Meaning
A dasymetric map is an improved choropleth map. A choropleth shades each whole administrative unit in one tone, as if the value were the same everywhere inside it. A dasymetric map uses extra information to redraw the zones first. For example, it removes forests, deserts, snowfields and water bodies before shading population density. Values then sit where people actually live. This gives a truer picture than a choropleth, which shows a sudden jump at every boundary.
Example
In Himachal Pradesh, the high snow-covered ranges have almost no people, and most people live in the valleys. A dasymetric density map leaves out the snow and bare rock, so the density is shown only in the lived-in valleys, not spread over the whole state.
Don't confuse with
- A choropleth map shades whole administrative units by their average value. A dasymetric map reshapes the zones to follow where the feature really exists.