Protractors

Like the triangle, most Alvin protractors are made of transparent plastic. They are available in 4-,6-, 8-, and 10-inch sizes and are either circular or semicircular in shape. Protractors are used for measuring and laying off angles other than those that may be drawn with the triangle or a combination of triangles. Most of the work you will do involving the use of the protractor will involve plotting information obtained from field surveys. 

Protractors used by the EA are usually graduated in increments of 1/2°. By careful estimation, angles of 1/4° may be obtained. Protractor numbering arrangement varies. Semicircular protractors are generally labeled from 0° to 180° in both directions. Circular protractors may be labeled from 0° to 360° (both clockwise and counterclockwise), or they may be labeled from 0° to 90° in four quadrants. 

Protractors should be stowed and cared for in the same manner as triangles.