# CIRCLE CIRCUMFERENCE

The measurement around the perimeter of a circle. To find the circumference, multiply Pi (3.142) by the diameter.

## Related Terms

### ABSOLUTE TEMPERATURE SCALE

A scale of temperature measurement in which zero degrees is absolute zero.

### HYDROGRAPHY

The science that deals with the measurement and description of the physical features of the oceans, seas, lakes, rivers, and their adjoining coastal areas, with particular reference to their use for navigation.

Radionavigation based on the measurement of the time differences in the reception of signals from several pairs of synchronized transmitters. For each pair of transmitters the isochrones are substantially hyperbolic. The combination of isochrones for two or more pairs of transmitters forms a hyperbolic lattice within which position can be determined according to the measured time differences

### THERMOGRAPHY

The use of infrared thermography whereby temperatures of a wide variety of targets can be measured remotely and without contact. This is accomplished by measuring the infrared energy radiating from the surface of the target and converting this measurement to an equivalent surface temperature.

### INFLUENCE QUANTITY

A quantity which is not the subject of the measurement but which influences the value of the quantity to be measured, or the indications of the measuring instrument, or the value of the material measure reproducing the quantity.

### ERROR OF MEASUREMENT

The discrepancy between the result of the measurement and the true value of the quantity measured. NOTE 1: In general, 'true value' may be replaced by 'conventional true value'. NOTE 2: The discrepancy can be expressed as either: the algebraic difference between these two values, i.e. (error of measurement) = (result of measurement) - (true value), or as the quotient of that difference and the value of the quantity measured. These two forms of expression are often identified as 'absolute error' and 'relative error' respectively.

### MEASUREMENT UNCERTAINTY

That part of the expression of the result of a measurement which states the range of values within which the true value or, if appropriate, the conventional true value is estimated to lie.

### GRAINS OF MOISTURE

The unit of measurement of actual moisture contained in a sample of air. (7000 grains - one pound of water).

### FOOT

1. the lower edge of any sail. 2. the bottom of a mast. 3. a measurement of 12 inches.

### SOUNDING

The measurement of the depth of water.