Drawing Arches and Circles

• One of the first things a student will learn to do with a compass is draw. By placing the spike arm of the compass firmly on paper, and rotating the drawing end around the fixed point, a perfectly symmetrical circle results. An arch or half-circle is simply a matter of dragging the pencil only halfway. This function of the compass is common for architecture and drafting. The size of the circle or arch is set by the angle formed by the arms. The desired radius, the distance from the center of a circle to its outer edge, is the illustrator's guide to setting the circle's size.
  
  

Measuring Distance

• A compass with two spikes and no pencil or drawing end is known as a "dividing compass," and it is used to measure distances on a map. The angle between the two spikes is set to equal some set distance on the map, using the scale. For example, if 1 inch equals 10 miles on a map, the compass will be set to 1 inch. Place one spike on the starting point,swiveling the compass toward the destination along the route. Count the number of swivels (or inches) between the two points. From there, return to the scale and calculate the distance.
  
  

Geometric Construction

• A compass can be used in geometry lessons to draw lines and shapes accurately. In concert with a straightedge, any shape can be drawn to accurate dimensions using a compass. An equilateral triangle, whose three sides are of the same length, can be drawn using a straight edge and a compass. Draw two dots along a straight line to represent the edges of the base of the triangle. Place the spike arm of the compass on one dot, and draw a circle with a radius the same length as the base. Place the spike arm on the other dot and draw an identical circle, intersecting the first. The spot where the two circles intersect at the top is the top point of the triangle, or apex. Use a straightedge to connect the dots.
  
  

Iconography

• The compass serves an aesthetic purpose as well as its intended practical uses. The image of the two-arms and a circular hinge has come to be a symbol of precision and careful thought in the West. Architecture firms and various educational institutions make use of this symbol. The Freemasons have one of the most universally recognized compass icons, their square and compass symbol, found on their buildings, documents and in jewelry. The prevailing notion on that symbol is that the compass represents the Freemasons' objective to keep their behavior within the bounds of honesty and morality.