Radiometric calibration is a general term used in science and technology for any set of calibration techniques in support of the measurement of electromagnetic radiation and atomic particle radiation. These can be for instance, in the field of
radiometry
Radiometry is a set of techniques for measurement, measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power (physics), power in space, as opposed to phot ...
or the measurement of
ionising radiation
Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...
radiated from a source.
Ionising radiation
![Radioactivity and radiation](https://upload.wikimedia.org/wikipedia/commons/6/6e/Radioactivity_and_radiation.png)
Ionising radiation is non-visible and requires the use of ionisation detectors such as the
Geiger Muller counter or
ion chamber
The ionization chamber is the simplest type of gas-filled radiation detector, and is widely used for the detection and measurement of certain types of ionizing radiation, including X-rays, gamma rays, and beta particles. Conventionally, the term ...
for its
detection and measurement. Instruments are calibrated using standards traceable to national laboratory radiation standards, such as those at The
National Physical Laboratory in the UK.
Count rate measurements are normally associated with the detection of particles, such as
alpha particle
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...
s and
beta particle
A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β∠...
s. However, for
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
and
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
dose measurements a unit such as the
gray
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
or
sievert
The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radi ...
is normally used.
The following table shows ionising radiation quantities in SI and non-SI units.
Satellite sensor calibration
Spectral data acquired by satellite sensors are influenced by a number of factors, such as atmospheric absorption, scattering, sensor-target-illumination geometry, sensor calibration, and image data processing procedures, which tend to change through time. Targets in multi-date scenes are extremely variable and have been nearly impossible to compare in an automated mode. In order to detect genuine landscape changes as revealed by changes in surface reflectance from multi-date satellite images, it is necessary to carry out radiometric correction. Two approaches to radiometric correction are possible: absolute and relative. The absolute approach requires the use of ground measurements at the time of data acquisition for atmospheric correction and sensor calibration. This is not only costly but also impractical when archival satellite image data are used for change analysis. The relative approach to radiometric correction, known as relative radiometric normalization (RRN), is preferred because no in-situ atmospheric data at the time of satellite overpasses are required. This method involves normalizing or rectifying the intensities or digital numbers (DN) of multi-date images band-by-band to a reference image selected by the analyst. The normalized images would appear as if they were acquired with the same sensor under similar atmospheric and illumination conditions to those of the reference image.
[Yang, Xiajun, and C. P. Lo. "Relative radiometric normalization performance for change detection from multi-date satellite images." Photogrammetric Engineering and Remote Sensing 66.8 (2000): 967-980.]
See also
*
Counts per minute
The measurement of ionizing radiation is sometimes expressed as being a ''rate'' of counts per unit time as registered by a radiation monitoring instrument, for which counts per minute (cpm) and counts per second (cps) are commonly used quantities ...
*
Radiometric resolution
Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring to ...
References
* Olsen, Doug; Dou, Changyong; Zhang, Xiaodong; Hu, Lianbo; Kim Hojin; Hildum, Edward. 2010.
Radiometric Calibration for AgCam Remote Sens. 2, no. 2: 464-477.
*D. Hall; G. Riggs; V. Salomonson. (1995). "Development of methods for mapping global snow cover using moderate resolution imaging spectroradiometer data." Remote Sensing of Environment. 54, no. 2: 127-140.
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Remote sensing
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