The contour interval is the isoline that is a function of the to variables and states the points of the equal intervals with reference to the sea levels and is illustrated on a topographic map, showing valleys, hills and steepness of slopes.
A contour interval shows the highest and lowest point of the gradient and another example is of the isopleth that is line of the equal interval of pressure.
The lines A and B are contour lines that show the low terrain or the features of lower heights and the elevation of Y is 446 meters and the point of W will be between the 100 to 300 like 200 or 250 meters. The X represents some mad made objects like a station.
