Custom Search
|
|
 
|
||
|
UNITS OF LINEAR MEASUREMENT Linear measure is used to express distances and to indicate the differences in their elevations. The standard units of linear measure are the foot and the meter. In surveying operations, both of these standard units are frequently divided into tenths, hundredths, and thousandths for measurements. When longer distances are involved, the foot is expanded into a statute or to a nautical mile and the meter into a kilometer. Table 1-1 shows the conversion factors for the common linear measurements. English Units In the English system, the most commonly used basic unit of linear measurement is the foot, a unit that amounts to slightly more than three-tenths of the international meter. In what is called ENGINEERS measurement, the foot is subdivided decimally; that is, into tenths, hundredths, or thousandths of a foot. In what is called CARPENTERS measurement, or English units, the foot is subdivided into twelfths called inches, and the inch is further subdivided into even-denominator fractional parts, as 1/2 in., 1/4 in., 1/8 in., and so on. Fractions or multiples of the basic 1-ft unit are used to form larger units of linear measure as follows:
A unit of linear measurement, called a VARA of Spanish and Portuguese origin, was formerly used to measure land boundaries in those areas of the United States that were at one time under Spanish control. In those areas old deeds and other land instruments still contain property descriptions in varas, which vary from state to state and country to country from 32 to 43 in.Metric Units In many of the non-English-speaking countries of the world, the most commonly used basic unit of linear measure is the meter. The length of a meter was originally designed to equal (and does equal very nearly) one ten-millionth part of the distance, measured along a meridian, between the earths equator and one of the poles. A meter equals slightly more than 1.09 yd.The big advantage of the metric system is the fact that it is a decimal system throughout; that is, the fact that the basic unit can be both subdivided into smaller units decimally and converted to larger units decimally by simply moving the decimal point in the appropriate direction. Names of units smaller than the meter are indicated by the Latin prefixes deci-(one-tenth), centi- (one-hundredth), mini- (one-thousandth), and micro- (one-millionth), as follows:
Names of units larger than the meter are indicated by the Greek prefixes deca- (ten), hecto- (one hundred), kilo- (one thousand), myria-(ten thousand), and mega- (one million), as follows:
|
 
|
|
|
||
