This activity is designed to provide practice in the application of Lessons 1, 2, 3 and 4.

Skills used:

• measure azimuth to distant known points
• convert magnetic to grid azimuth
• determine back azimuth
• plot back azimuth

Mastering the first three lessons, along with this last student activity, will allow individuals to plot their location on a topographical map using the Resection method

Definition: Resection - method of locating your position on a map by determining the back direction from two well-defined distant known points.

1. Determine the azimuth (direction in degrees) to numerous distant known locations.

2. Convert magnetic azimuths to grid azimuths

3. Convert grid azimuths to back azimuths

4. Draw the back azimuths on the map

5. Identify your location on the map

In an outdoor environment, utilizing the skills developed in the four lessons, students working in pairs will accomplish the five steps in identifying their location using Resection

Students must use a topographical map of their location.

1. Orient the map towards North using the compass.

2. Measure the magnetic azimuth to a distant known location. The examples here are not the exercises but steps to use. Students will have to pick distant known points in their locations. These locations must be identifiable by their ability to see them visually and identify them on the map. In the example below we will use Hill 107 (A). We measure the azimuth with a lensatic compass. The magnetic azimuth to Hill 107 is 335 degrees.

3. We determine the declination to be plus 10 degrees. The magnetic azimuth plus 10 gives us a grid azimuth of 345. (335+10=345).

4. Since 345 is more than 180 we will subtract 180 to determine the back azimuth from Hill 107. (345-180=165)

5. Using a protractor, we line up the vertical cross hair with a North and South grid line. Use a straight edge. Line one end of the edge with the degree reading of 165 on the outside of the protractor. Align the straight edge with the center of Hill 107 and a degree reading 165 on the outside of the protractor. Make sure the vertical cross hair in the center of the protractor is aligned with a North and South grid line. We make a dot in the center of the protractor and at the tick mark for 165. Remove the straight edge and connect the tick marks using a pencil (never use ink or you will be unable to correct errors).

6. Measure a second distant known point. Like the first magnetic azimuth this must be one the student can see and associate with the map. As a second point we are going to use the road junction (B). We determine the magnetic azimuth to be 35 degrees.

7. The the declination of 10 degrees does not change. The magnetic azimuth plus 10 gives us a grid azimuth of 45. (35+10=45).

8. Since 45 is less than 180 we will add 180 to determine the back azimuth from the road junction. The back azimuth is 225 degrees (45+180=225).

9. Using a protractor we line up the vertical cross hair with the a North South grid line. Using a straight edge we line up the degree reading of 225, the road intersection, and the center of our protractor. Mark two tick marks (center of protractor and outside protractor. Remove the protractor and make a line between the tick marks.

10. The point where the two lines intersect is our location.

Helpful World Wide Web Pages:

Student Resources:

Outside environment

1. Lensatic Compass

2. Topographic map of Location

3. ruler or straight edge

3. Three identifiable distant known points

4. Writing paper

5. Pencil no pens

Instructor Resource:

Known direction to the 5 major identifiable known points

This exercise will be a 'go' or 'no-go' endeavor for this drill

To receive a 'go' the students must:

• draw two back azimuths on his map
• the two azimuths must intersect within 300 meters of his location

Students not receiving a 'go' will seek the assistance of an instructor.

Assistant instructors will be students who have received a 'go' and have been instructed on the required teaching techniques.