There may be times when the distance you are measuring exceeds the graphic scale. In these cases, you will need to place an intermediate tick mark (C) at the 1,000-meter mark on the extension scale. You know that the point from point (B) to point (C) is 6,000-meters. Now, measure the distance between point (C) and point (A), again using your extension scale. In this example, the distance between points (C) and (A) is 420-meters. Your total distance between points (B) and (A) then becomes 6,420-meters (6,000-meters + 420-meters = 6,420-meters).

In this example, the right tick mark (B) is aligned with the 3,000-meter mark on the primary scale. To determine the total distance to the nearest 10-meters, look at the extension scale. The extension scale is marked in alternating shaded blocks, each block representing 100-meters. The left tick mark (A) falls halfway between the 200-meter and 300-meter blocks, thus it represents 250-meters. The total distance between our two points (A,B) is 3,250-meters (3,000-meters + 250-meters = 3,250-meters).

To convert map distance to ground distance, move your paper down to the appropriate graphic bar scale located on the bottom of your map. Align the right tick mark (B) with the printed number in the primary scale so that the left tick mark (A) is in the extension scale.

Place the edge of your paper on the map touching the edge of both points. Your paper should extent beyond both points. Make a tick mark on the edge of the paper at each point. Remember that the center of a topographic symbol designates the true location of the object on the ground.

Step 1: Placement

Step 2: Convert

Step 3: Measure

Step 4: Distance