![Sirius A and B Hubble photo](https://upload.wikimedia.org/wikipedia/commons/f/f3/Sirius_A_and_B_Hubble_photo.jpg)
In
natural science and
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
, an artifact or artefact is any
error
An error (from the Latin ''error'', meaning "wandering") is an action which is inaccurate or incorrect. In some usages, an error is synonymous with a mistake. The etymology derives from the Latin term 'errare', meaning 'to stray'.
In statistics ...
in the perception or representation of any information introduced by the involved equipment or technique(s).
Computer science
In ''
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includi ...
'',
digital artifact
Digital artifact in information science, is any undesired or unintended alteration in data introduced in a digital process by an involved technique and/or technology.
Digital artifact can be of any content types including text, audio, video, ...
s are anomalies introduced into digital signals as a result of
digital signal processing.
Microscopy
In ''
microscopy'',
visual artifact
Visual artifacts (also artefacts) are anomalies apparent during visual representation as in digital graphics and other forms of imagery, especially photography and microscopy.
In digital graphics
* Image quality factors, different types of vi ...
s are sometimes introduced during the processing of samples into
slide
Slide or Slides may refer to:
Places
* Slide, California, former name of Fortuna, California
Arts, entertainment, and media Music Albums
* ''Slide'' (Lisa Germano album), 1998
* ''Slide'' (George Clanton album), 2018
*''Slide'', by Patrick Glees ...
form.
Econometrics
In ''
econometrics
Econometrics is the application of statistical methods to economic data in order to give empirical content to economic relationships. M. Hashem Pesaran (1987). "Econometrics," '' The New Palgrave: A Dictionary of Economics'', v. 2, p. 8 p. 8 ...
'', which trades on computing relationships between related
variables, an artifact is a spurious finding, such as one based on either a faulty choice of variables or an over-extension of the computed relationship. Such an artifact may be called a ''statistical artifact''. For instance, imagine a hypothetical finding that presidential
approval rating
An opinion poll, often simply referred to as a survey or a poll (although strictly a poll is an actual election) is a human research survey of public opinion from a particular sample. Opinion polls are usually designed to represent the opinions ...
is approximately equal to twice the percentage of citizens making more than $50,000 annually; if 60% of citizens make more than $50,000 annually, this would predict that the approval rating will be 120%. This prediction is a statistical artifact, since it is spurious to use the
model
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure.
Models c ...
when the percentage of citizens making over $50,000 is so high, and gross error to predict an approval rating greater than 100%.
Remote sensing
Medical imaging
In
medical imaging
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...
, artifacts are misrepresentations of tissue structures produced by imaging techniques such as
ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
,
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 ...
,
CT scan, and
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI). These artifacts may be caused by a variety of phenomena such as the underlying physics of the energy-tissue interaction as between ultrasound and air,
susceptibility artifacts, data acquisition errors (such as patient motion), or a reconstruction
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
's inability to represent the anatomy. Physicians typically learn to recognize some of these artifacts to avoid mistaking them for actual
pathology
Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...
.
In ultrasound imaging, several assumptions are made from the computer system to interpret the returning echoes. These are: echoes originate only from the main ultrasound beam (while there are side lobes and grating lobes apart from the main ultrasound beam); echoes returns to transducer after a single reflection (while an echo can be reflected several times before reaching the transducer); depth of an object relates directly to the amount of time for an echo to reach the transducer (while an echo may reflect several times, delaying the time for the echo return to the transducer); speed of ultrasound in human tissue is constant, echoes travel in a straight path. and acoustic energy of an echo is uniformly attenuated. When these assumptions are not maintained, artifacts occur.
Medical electrophysiological monitoring
In medical
electrophysiological
Electrophysiology (from Greek , ''ēlektron'', "amber" etymology of "electron"">Electron#Etymology">etymology of "electron" , ''physis'', "nature, origin"; and , ''-logia'') is the branch of physiology that studies the electrical properties of bi ...
monitoring, artifacts are anomalous (interfering) signals that originate from some source other than the electrophysiological structure being studied. These artifact signals may stem from, but are not limited to: light sources; monitoring equipment issues; utility frequency (50 Hz and 60 Hz); or undesired electrophysiological signals such as
EMG presenting on an
EEG
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...
-,
EP-,
ECG
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the hear ...
-, or
EOG- signal. Offending artifacts may obscure, distort, or completely misrepresent the true underlying electrophysiological signal sought.
Radar
![Multipath propagation diagram en](https://upload.wikimedia.org/wikipedia/commons/f/f2/Multipath_propagation_diagram_en.svg)
In
radar signal processing
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, ...
, some echoes can be related to fixed objects (
clutter
Clutter and its derivations may refer to any of the following:
Excessive physical disorder
* Clutter, a confusing, or disorderly, state or collection, and possible symptom of compulsive hoarding
* Clutter (marketing), numerous advertisements, a ...
), multipath returns,
jamming, atmospheric effect (
brightband or
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...
),
anomalous propagation Anomalous propagation (sometimes shortened to anaprop or anoprop) Peter Meischner (ed.), ''Weather Radar: Principles and Advanced Applications'', Springer Science & Business Media, 2005, page 144 includes different forms of radio propagation due to ...
, and many other effects. All those echoes must be filtered in order to obtain the position, velocity and type of the real targets that may include aircraft, and weather.
See also
*
Sonic artifact
In sound and music production, sonic artifact, or simply artifact, refers to sonic material that is accidental or unwanted, resulting from the editing or manipulation of a sound.
Types
Because there are always technical restrictions in the way a ...
, in sound and music production, sonic material that is accidental or unwanted, resulting from the editing of another sound.
*
Visual artifact
Visual artifacts (also artefacts) are artifact (error), anomalies apparent during visual representation as in digital graphics and other forms of imagery, especially photography and microscopy.
In digital graphics
* Image quality#Image quality f ...
, in imaging, any unwanted visual alteration introduced by the imaging equipment.
*
Compression artifact
A compression artifact (or artefact) is a noticeable distortion of media (including images, audio, and video) caused by the application of lossy compression. Lossy data compression involves discarding some of the media's data so that it beco ...
, in computer graphics, distortion of media by the data compression.
References
{{DEFAULTSORT:Artifact (Error)
Error
Optical illusions
Data compression
Radar theory