 An engineer scale can be used to estimate straight line distances on a topo map. To do this, first determine map scale using the scale bar or representative fraction printed on the map. For this example, the map scale is 1 to 24,000, which means that 1 inch on the map represents 24,000 inches on the ground. To determine feet, divide 24,000 by 12 inches per foot. So in this case, 1 inch on the map is equal to 2,000 feet on the ground. Knowing that, we can then determine which side of the scale we should use to make our distance measurements. Because 1 inch equals 2,000 feet on this map, we can use the 20 side of the engineer scale to make distance measurements. Each tick mark will represent 100 feet, making the number 1 on the scale equal 1,000 feet and the number 2 equal 2,000 feet. To determine the straight line distance, place the 0 mark on your starting point and line up the scale to your desired end point. Then count the tick marks between the two points. In this example, the starting point is the Dixie Lookout Tower and our end point is a small structure at the end of an unimproved road. When we count the tick marks between the two points, we see we have 67 tick marks. Remembering that each tick mark is equal to 100 feet, we multiply the number of tick marks by 100, or 67 times 100 equals 6,700 feet. To determine distance in miles, divide the number of feet by 5,280 feet in a mile. So the straight line distance in miles between the two points is 6,700 divided by 5,280 feet in a mile equals 1.26 miles.