In certain types of measurement, when the existing temperature differs from a standard temperature, the measured values will be in error and must be corrected, In each of the several temperature-measurement scales, the unit of measure is called a DEGREE, which varies for the different temperature scales, When the scale extends below zero, values below zero are identified by a minus sign. Temperatures are writ-ten, for example, as 23F or 5C, the letter designating the particular temperature scale. To avoid confusion when writing or talking about temperature, we should always be sure to indicate the type of scale used, Two of the most commonly used temperature scales are the CENTIGRADE scale and the FAHRENHEIT scale.

On the Centigrade scale (also known inter-nationally as "Celsius Scale" after Anders

Celsius, a Swedish astronomer who first devised it), zero is the freezing point of water, and plus 100 is its boiling point.

On the Fahrenheit scale, the temperature of the freezing point of water is plus 32, and its boiling point is plus 212.

Now let us compare these scales. A Fahrenheit degree represents five-ninths of the change in heat intensity indicated by a degree on the Centigrade scale. Temperatures on either of the two scales can be converted to the other by the following formulas:

Note that, when converting Fahrenheit to Centigrade, you should first subtract the 32, then multiply by 5/9. When converting Centigrade to Fahrenheit, you should first multiply by 9/5, then add the 32.

Measurements of atmospheric pressure are used in surveying to determine approximate differences in elevation between points on the earths surface and to determine the best approximate correction for the effect of atmos-pheric refraction. The units of measure for atmospheric pressure and their relationships are as follows:

    = 1,03323 kilograms per square centimeter

    = 1.01325 bars, or 1013.25 millibars

Dry measure is a system of measure of volume used in the United States for dry commodities, such as grains, fruits, and certain vegetables. The basic unit in dry measure is the BUSHEL. The standard U.S. bushel contains about 77.6 lb of water. Since there are about 62.4 lb of water in a cu ft, it follows that a U.S. bushel has a volume of

Board measure is a method of measuring lumber in which the basic unit is a BOARD FOOT (bf). A board foot is an abstract volume 1 ft long by 1 ft wide by 1 inch thick. The chief practical use of board measure is in cost calculations; lumber is sold by the board foot just as sugar is sold by the pound.

There are several formulas for calculating the number of board feet in any given length of lumber of given section dimensions. Because lumber dimensions are most frequently given by length in feet and width and thickness in inches, the following formula is probably the most practical:

Board measure is calculated on the basis of the nominal, not the actual, section dimensions. The actual section dimensions of (for example) 2 by 4 stock, which is surfaced on all four surfaces (S4S), are about 1 5/8 in. thick by 3 5/8 in. wide. Nevertheless, the computation for the number of (for example) 300 linear ft of 2 by 4 stock would be as follows: