The precision of a map / plan depends on the fineness and accuracy with which the details are plotted. Moreover, the plotting accuracy on paper, varies between 0. 1 mm to 0.4 mm, of which the mean value of 0.25 mm is usually adopted as plotting accuracy. This, therefore, imposes limit on linear measurements that can be represented on the map at a given scale and thus accuracy. The measurements to be made on the ground. For example, if the plotting scale is 1: 1000, than the maximum possible distance on ground, that can be represented as map, is 0.25 x 1,000 mm i.e., 0.25 meter. Thus, any detail having length less than 0.25 meter can not be plotted and thus, field measurement for objects having dimension less than 0.25 meter are not needed. If the scale is still smaller say 1: 50,000, then maximum plottable ground distance is 0.25 x 50,000mm i.e., 12.5 meter. Thus any object having length or width less than 12.5 meter, such as roads, railway track, etc. cannot be plotted on map. However, if the features are important and can not be ignored, these are represented on map by proper conventional signs and colours adopting the ‘Principles of Generalisation' of Details.

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