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Precautions taken while constructing choropleth map.

Answer Text:
Precautions taken while constructing choropleth map.
(i) The shading should show a progressive increase in density.
-Avoid a blank because it can give the wrong impression of zero density. Example of different methods of shading.
(ii) The range of values may be divided into groups by either arithmetic progression, when the range is not
great. E.g 1-10, 11-20, 21-30, or a geometric progression e.g 1-10, 11-20, 21-40, 41-80, 81-160, 161-320
(iii) Variation in density can also be shown by proportional shading i.e by drawing horizontal lines close together to represent increase in density.
e.g see the bars below.
(iv) Do not show variation in density by merely drawing lines at different angles.
e.g.
(v) A more pleasing appearance of continuity and transition can be
achieved if shading lines are “carried across” as far as possible.
(vi) It is advisable to use a key with individual boxes.