What is the purpose of placing bar scales on maps? Solution A bar scale is placed on maps so that after a number of years when the map is used,there will be distortion of the map (paper on which map is drawn). So the Scale specified on map may not give the correct distance on field as the map is distorted. There will be proportional distortion of the bar scale drawn on map. By the use of this proportional distortion we can get the correct distance on field..