Dewpoint is the temperature to which air must be cooled to reach its saturation point. The cooling must be done at a constant pressure and moisture content. A rising dewpoint indicates increasing moisture.

Wet bulb temperature is the lowest temperature to which the current air can be cooled. Cooling is achieved by evaporating water into air at a constant pressure. Wet bulb temperature is measured by a psychrometer. The greater the difference is between wet and dry bulb temperatures, the drier the air is.

Base and meridian lines are similar to latitude and longitude lines. Use geographic locations, such as prominent features of the area, as reference points.

Townships are rectangular blocks of land about 6 miles square. The squares are gridded and numbered according to their position north or south of the base line.

Ranges are columns of townships set side by side. They are numbered starting at the meridian that runs through the point of origin of each system. Ranges run east and west.

Latitude and longitude are measuring lines used for locating places on the surface of the Earth. They are angular measurements, expressed as degrees of a circle. A full circle contains 360°. Each degree can be divided into 60 minutes, and each minute is divided into 60 seconds. The symbol for minutes is (´) and for seconds is ("). 

Resection is a method of finding one's own location on a map by sighting two known landmarks.
The procedure is as follows:

1. Find at least two landmarks on the map that can be also identified on the ground. With a compass measure an azimuth to each of the landmarks on the ground.
2. Adjust for declination.
3. Convert to back azimuths.
4. Using the two known landmarks on the map, draw the lines of the back azimuths until the lines cross.
5. The location is where the two lines cross.

Intersection is a method of locating a point on a map by intersecting lines from two known landmarks on the ground. Intersection is one method fire lookouts use in determining the location of a fire. The procedure is as follows:

A closed traverse is a series of connected lines whose lengths and bearings are measured off these lines (or sides), which enclose an area. A closed traverse can be used to show the shape of the perimeter of a fire or burn area. If you were to pace continuously along the sides of a closed traverse, the finishing point would be the same as the starting location.

A vector has a magnitude (often representing distance or speed) and direction. When a clinometer (see Section 4.5) is used to estimate the slope percent and the slope length is measured with a metal tape, the result is a vector. The slope length represent the magnitude and the slope percent can be converted into a slope angle that represents direction. Vectors can provide information about the distance and direction of fire spread, or the speed and direction of fire spread or wind. 

The magnetic reference for Earth is north regardless of whether you are traveling north or south. Magnetic declination, or declination, is the difference between the true north reading from the map and the magnetic north reading from a compass. When a compass is used in combination with a map, a correction must be made to allow for declination.

A compass is an instrument used to determine direction in fire control work. An azimuth compass is graduated/marked with a full circle of 360 degrees called an azimuth circle. Compass components include a magnetic needle that always points to magnetic north, a graduated circle for laying off angles from true north, and a sighting line for extending a line of sight while following a course of direction. The north end of the needle is marked with a small arrow.