User notes: Weights should add up to a total of 100. Distance & Length Select your preferred method of calculating road and section distances. a) Great Circle distance calculations eliminate the need for maps or mapping knowledge and may be adequate for most locations. b) Map constants may be derived from any topographical map that covers the area of the road network being managed. Layout feet and minutes for North to South on a nearly central vertical line on the map; East to West on a nearly central horizontal line.