1. A reference to the verification of the accuracy of an instrument by comparing the measurements or other data which are provided with that of a valid standard which have been proven to be trustworthy.
2. Pertaining to a size of vessels or the calibers of tube-like parts.

1. The specification and measurements of the properties or performances of a device so it can be used for subsequent measuring procedures.
2. The dimensions of the size of a tube, or the determination or correction of the lines on a round structure similar to a pipe.

In mapping, a line on which markers are placed at intervals which are accurately measured so they can be used for distance-measuring instruments or equipment.

The numerical results which are used to determine if aerial cameras are giving the proper focal length of the camera-lens unit and the relationship of principal points of a photograph to the fixed standard marks of a camera and significant corrections for the lens distortion.

A line that gives the correct value for each indicated reading of a meter or control dial.

A test shooting that is intended to determine the necessary corrections for each gun or launcher of a battery to hit the intended target or targets: The calibration fire is used in order to make sure all the weapons hit the same points or that the impacts have the desired patterns.

On a radar screen, the electronically generated marks that provide numerical values for the navigational parameters; such as, bearing, distance, height, and/or time.

A glass negative that has been exposed with its emulsion side in the same position as that which is presented by the service emulsion at the time of exposure, providing a record of the distance between the camera's fiducial marks or references for comparisons or measurements.

In ordnance dealing with weapons, the point at which synchronized firing is directed.

A special signal that helps ships or aircraft to find their positions and which is operated primarily for determining shipboard radio direction-finders by transmitting continuously during specifically scheduled hours or whenever it is desired.

Any of the various types of standards that indicate whether an analytical instrument or procedure is working within he prescribed limits: Some calibration references the testing of solutions used with pH meters, and solutions with known concentrations of standard solutions that are used with spectrophotometers or devices used to compare two light radiations wavelength by wavelength.

A pattern which is made in accordance with an aerial camera to show the relationship of the principal point of a camera to its standard symbols, for rapid and accurate marking of the principal points on a series of photographs.