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In situ (Template:PronEng) is a Latin phrase meaning in the place. It is used in many different contexts.

Aerospace

In the aerospace industry, equipment on board aircraft must be tested "in situ", or in place, to confirm everything functions properly as a system. Individually, each piece may work but interference from nearby equipment may create problems not anticipated. Special test equipment is available for this "in situ" testing.

Archaeology

In archaeology, "in situ" refers to an artifact that has not been moved from its original place of deposition. In other words, it is stationary, meaning "Still". An artifact being "in situ" is critical to the interpretation of that artifact and, consequently, to the culture which formed it. Once an artifact's 'find-site' has been recorded, the artifact can then be moved for conservation, further interpretation and display. An artifact that is not discovered "in situ" is considered out of context and will not provide an accurate picture of the associated culture. However, the out of context artifact can provide scientists with an example of types and locations of "in situ" artifacts yet to be discovered.

"In situ" only expresses that the object has not been "newly" moved. Thus, an archaeological in-situ-find may be an object that was historically looted from another place, an item of "booty" of a past war, a traded item, or otherwise of foreign origin. Consequently, the "in situ" find site may still "not" reveal its provenance but with further detective work may help uncover links that otherwise would remain unknown. It is also possible for archaeological layers to be reworked on purpose or by accident (by humans, natural forces or animals). For example, in a "tell-tell mound", where layers are not typically uniform or horizontal, or in land cleared or tilled for farming.

The term "In situ" is often used to describe ancient sculpture that was carved in place such as the Sphinx or Petra. This distinguishes it from statues that were carved and moved like the Colossi of Memnon which was moved in ancient times.

Architecture

In architecture and building, in situ means construction which is carried out on the building site using raw materials. Compare that with prefabricated construction, in which building components are made in a factory and then transported to the building site for assembly. For example, concrete slabs may be in situ or prefabricated.

In situ techniques are often more labour-intensive, and take longer, but the materials are cheaper, and the work is versatile and adaptable. Prefabricated techniques are usually much quicker, therefore saving money, but factory-made parts can be expensive. They are also inflexible, and must often be designed on a grid, with all details fully calculated in advance. Finished units may require special handling due to excessive dimensions.

Art

In art, in situ refers to a work of art made specifically for a host site, or that a work of art takes into account the site in which it is installed or exhibited. For a more detailed account see: Site-specific art.

Astronomy

Future space exploration or terraforming may rely on obtaining supplies in situ, such as previous plans to power the Orion space vehicle with fuel minable on the moon.
Mars Direct mission concept is based primarily on the in situ fuel production using Sabatier reaction.

A fraction of the globular star clusters in our Galaxy, as well as those in other massive galaxies, might have formed in situ. The rest might have been accreted from now defunct dwarf galaxies.

Biology

In biology, in situ means to examine the phenomenon exactly in place where it occurs (i.e. without moving it to some special medium). This usually means something intermediate between in vivo and in vitro. For example, examining a cell within a whole organ intact and under perfusion may be in situ investigation. This would not be in vivo as the donor is sacrificed before experimentation, but it would not be the same as working with the cell alone (a common scenario in in vitro experiments).

In-vitro was the first of humankind’s attempts to qualitatively and quantitatively analyze natural occurrences in the lab. Eventually, the limitation of in-vitro experimentation was that they were not conducted in natural environments. To compensate for this problem, in-vivo experimentation allowed testing to occur in the originate organism or environment. To bridge the dichotomy of benefits associated with both methodologies, in-situ experimentation allowed the controlled aspects of in-vitro to become coalesced with the natural environmental compositions of in-vivo experimentation.

In oncology: for a carcinoma, in situ means that malignant cells are present as a tumor but has not metastasized, or invaded, beyond the original site where the tumor was discovered. This can happen anywhere in the body, such as the skin, breast tissue, or lung.

In conservation of genetic resources, "in-situ conservation" (also "on-site conservation") is the process of protecting an endangered plant or animal species in its natural habitat, as opposed to ex-situ conservation (also "off-site conservation").

Chemistry and chemical engineering

In chemistry, in situ typically means "in the reaction mixture." There are numerous unstable molecules which must be synthesized in situ (i.e. in the reaction mixture but cannot be isolated on their own) for use in various processes. Examples include the Corey-Chaykovsky reagent and adrenochrome.

In chemical engineering, in situ often refers to industrial plant "operations or procedures that are performed in place". For example, aged catalysts in industrial reactors may be regenerated in place (in situ) without being removed from the reactors.

Computer science

In computer science an in situ operation is one that occurs without interrupting the normal state of a system. For example, a file backup may be restored over a running system, without needing to take the system down to perform the restore. In the context of a database, a restore would allow the database system to continue to be available to users while a restore happened. An in situ upgrade would allow an operating system, firmware or application to be upgraded while the system was still running, perhaps without the need to reboot it, depending on the sophistication of the system.

An algorithm is said to be an in situ algorithm, or in-place algorithm, if the amount of memory required to execute the algorithm is O(1), that is, does not exceed a constant no matter how large the input. For example, heapsort is an in situ sorting algorithm.

In designing user interfaces, the term in situ means that a particular user action can be performed without going to another window, for example, if a word processor displays an image and allows you to edit the image without launching a separate image editor, this is called in situ editing.

Earth and atmospheric sciences

In physical geography and the Earth sciences, in situ typically describes natural material or processes prior to transport. For example, in situ is used in relation to the distinction between weathering and erosion, the difference being that erosion requires a transport medium (such as wind, ice, or water), whereas weathering occurs in situ. Geochemical processes are also often described as occurring to material in situ.

In the atmospheric sciences, in situ refers to obtained through direct contact with the respective subject, such as a radiosonde measuring a parcel of air or an anemometer measuring wind, as opposed to remote sensing such as weather radar or satellites.

Electrochemistry

In electrochemistry, the phrase in situ refers to performing electrochemical experiments under operating conditions of the electrochemical cell ie, under potential control. This is opposed to doing ex situ experiments that are performed under the absence of potential control. Potential control preserves the electrochemical environment essential to maintain the double layer structure intact and the electron transfer reactions occurring at that particular potential in the electrode/electrolyte interphasial region.

Space sciences

In the space sciences, in situ refers to measurements of the particle and field environment that the satellite is embedded in, such as the detection of energetic particles in the solar wind, or magnetic field measurements from a magnetometer.

Environmental engineering

In situ can refer to where a clean up or remediation of a polluted site is performed using and simulating the natural processes in the soil, contrary to ex situ where contaminated soil is excavated and cleaned elsewhere, off site.

Literature

In literature in situ is used to describe a condition. The Rosetta Stone, for example, was originally erected in a courtyard, for public viewing. Most pictures of the famous stone are not "in-situ" pictures of it erected, as it would have been originally. The stone was uncovered as part of building material, within a wall. Its in situ condition today is that it is erected, vertically, on public display at the British Museum in London, England.

Linguistics

In linguistics, specifically syntax, an element may be said to be in situ if it is pronounced in the position where it is interpreted. For example, questions in languages such as Chinese have in-situ wh-elements, with structures comparable to "John bought what?" while English wh-elements are not in-situ (see wh-movement): "What did John buy?"

Law

In legal context, in situ is often used for its literal meaning. For example, in Hong Kong, in situ land exchange involves the government exchanging the original or expired lease of a piece of land with a new grant or re-grant with the same piece of land or a portion of that.

Medicine

Cancer in situ means cancer that is in one place. This type of cancer can often, depending on where it is located, be removed by surgery.

Petroleum production

In situ means "in place", and refers to recovery techniques which apply heat or solvents to heavy oil or bitumen reservoirs beneath the earth. There are several varieties of in situ technique, but the ones which work best in the oil sands use heat.

RF transmission

In radio frequency (RF) transmission systems, in situ is often used to describe the location of various components while the system is in its standard transmission mode, rather than operation in a test mode. For example, if an in situ wattmeter is used in a commercial broadcast transmission system, the wattmeter can accurately measure power while the station is "on the air".

Military/Police/engineering

Destroy in situ, commonly used as an order to detonate an explosive device (bomb, landmine etc.) as opposed to transporting it to another location for disposal.

S.I.T.U

Satellite Identification and Tracking Unit. A now defunct, once elite Canadian AirForce unit of NORADS' Space Command. Located in New Brunswick Canada, and was stood down in May 1992. The unit utilized a 4 ton Baker Nunn camera.

References

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 In [[biology]], ''in situ'' means to examine the phenomenon exactly in place where it occurs (i.e. without moving it to some special medium). This usually means something intermediate between ''[[in vivo]]'' and ''[[in vitro]]''. For example, examining a [[w:cell (biology)|cell]] within a whole [[organ (anatomy)|organ]] intact and under [[perfusion]] may be ''in situ'' investigation. This would not be ''in vivo'' as the donor is sacrificed before experimentation, but it would not be the same as working with the cell alone (a common scenario in ''in vitro'' experiments).
-In-vitro was the first of humankind’s attempts to qualitatively and quantitatively analyze natural occurrences in the lab<ref name="citation pending">citation pending</ref>. Eventually, the limitation of in-vitro experimentation was that they were not conducted in natural environments. To compensate for this problem, in-vivo experimentation allowed testing to occur in the originate organism or environment<ref name="citation pending"/>. To bridge the dichotomy of benefits associated with both methodologies, in-situ experimentation allowed the controlled aspects of in-vitro to become coalesced with the natural environmental compositions of in-vivo experimentation.
+In-vitro was the first of humankind’s attempts to qualitatively and quantitatively analyze natural occurrences in the lab. Eventually, the limitation of in-vitro experimentation was that they were not conducted in natural environments. To compensate for this problem, in-vivo experimentation allowed testing to occur in the originate organism or environment. To bridge the dichotomy of benefits associated with both methodologies, in-situ experimentation allowed the controlled aspects of in-vitro to become coalesced with the natural environmental compositions of in-vivo experimentation.
 In [[oncology]]: for a [[carcinoma]], ''in situ'' means that [[malignant]] cells are present as a tumor but has not metastasized, or invaded, beyond the original site where the tumor was discovered. This can happen anywhere in the body, such as the skin, breast tissue, or lung.