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Question
What is an Isopleth map? How an interpolation is carried out?
Solution
The word Isopleth is derived from Iso meaning equal and pleth means lines. Thus, an imaginary line, which joins the places of equal values, is referred to as Isopleth. The more frequently drawn isopleths include Isotherm (equal temperature), Isobar (equal pressure), Isohyets (equal rainfall), Isonephs (equal cloudiness), Isohels (equal sunshine), contours (equal heights), Isobaths (equal depths), Isohaline (equal salinity), etc. Interpolation is used to insert the intermediate values between the observed values of two stations/locations, such as temperature recorded at Chennai and Hyderabad or the spot heights of two points. Generally, drawing of isopleths joining the places of the same value is also termed as interpolation.
Methods of Interpolation:
- Firstly, determine the minimum and maximum values given on the map.
- Calculate the range of value, i.e. range = maximum value – minimum value.
- Based on range, determine the interval in a whole number like 5, 10, 15, etc.
- The exact point of drawing an isopleth is determined by using the following formula
`"Point of Isopleth"= "Distance between two points in cm" /"Difference between the two values of corresponding points"× "Interval"`
