Graphing is a method of showing the relationship between two or more sets of data by means of a chart or sketch. Trends in data are easier to identify with a graph than a data table.

A graph can be created using graphing paper (you purchase gridded paper or draw your own), a computer application such as Excel, or graphing applications for a personal digital assistant (PDA) or phone. A graph shows a set of data points plotted in relation to the horizontal axis and vertical axis. 

A chain is equal to 66 feet and is the basic unit for measuring distances in fire-control work. There are 80 chains in 1 mile.

A pace is the distance on level ground between the heel of one foot and the heel of the same foot where it next touches the ground while walking normally (two normal steps). As everyone's pace differs, it is important to determine one's individual pace length.

Slope refers to the angle, or grade, of an incline. Slope can be upward or downward. Slope is typically expressed as a percent, and corresponds to the amount of rise, or vertical distance, divided by the run, or horizontal distance. Percentage means per 100. Slope can also be expressed as an angle, which gives the amount of deviation from flat as a number of degrees. Conversions between slope percent and slope angle can be done using a scientific calculator and the inverse tangent (arc tan) function.

Degrees are the unit of measure used for angles, just as feet are used to measure distance. The symbol for degrees is "°". There are 360° in a full circle, and 90° in a right angle. A protractor is used for measuring angles. As shown below, a protractor is a half or full circle measuring device, marked in degrees along the outer edge, with a straight line running from 0° to 180°. There is a small hole in the center of the protractor. To use a protractor: 

Angles are formed when two or more lines come together at a point. The angle in the image below is 45 degrees. A right angle, where the two lines are perpendicular to each other, is 90 degrees. The closer together the two lines, the smaller the angle.

Friction loss comparison of the forestry hose and hose on the Forest Service qualified products lists for 5100-186 and 5100-187 in units of pounds per square inch per 100 feet.