In situ is a Latin phrase that translates literally to "on site" or "in position".
It means "locally", "on site", "on the premises" or "in place" to describe an event where it
takes place, and 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 unanticipated
problems.
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,
of 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 as not providing
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.
When excavating a burial site or surface deposit "in situ" refers to cataloging, recording,
mapping, photographing human remains in the position they are discovered.
The label in situ indicates only 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.
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.
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.
The term can also refer to a work of art created at the site where it is to be displayed, rather
than one created in the artist's studio and then installed elsewhere.
Astronomy 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 and biomedical engineering
In biology and biomedical engineering, in situ means to examine the phenomenon exactly
in place where it occurs.
In the case of observations or photographs of living animals, it means that the organism
was observed in the wild, exactly as it was found and exactly where it was found.
The organism had not been moved to another location such as an aquarium.
This phrase in situ when used in laboratory science such as cell science can mean 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 by experimentation, but it would
not be the same as working with the cell alone.
In vitro was among the first 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 conservation of genetic resources, "in situ conservation" is the process of protecting
an endangered plant or animal species in its natural habitat, as opposed to ex situ conservation.
Chemistry and chemical engineering In chemistry, in situ typically means "in
the reaction mixture."
There are numerous situations in which chemical intermediates are synthesized in situ in various
processes.
This may be done because the species is unstable, and cannot be isolated, or simply out of convenience.
Examples of the former 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 without
being removed from the reactors.
Civil engineering In architecture and building, in situ refers
to construction which is carried out at 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.
The phrase may also refer to those assets which are present at or near a project site.
In this case, it is used to designate the state of an unmodified sample taken from a
given stockpile.
Site construction usually involves grading the existing soil surface so that material
is "cut" out of one area and "filled" in another area creating a flat pad on an existing slope.
The term "in situ" distinguishes soil still in its existing condition from soil modified
during construction.
The differences in the soil properties for supporting foundations, accepting underground
utilities, and shedding storm water persist indefinitely.
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 extra 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.
In Big Data space, in situ data would mean bringing the computation to where data is
located, rather than the other way.
like in traditional RDBMS systems where data is moved to computational space.
Design and advertising In design and advertising the term typically
means the superimposing of theoretical design elements onto photographs of real world locations.
This is a pre-visualization tool to aid in illustrating a proof of concept.
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, 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.
Economics In economics, in situ is used when referring
to the in place storage of a product, usually a natural resource.
More generally, it refers to any situation where there is no out-of-pocket cost to store
the product so that the only storage cost is the opportunity cost of waiting longer
to get your money when the product is eventually sold.
Examples of in situ storage would be oil and gas wells, all types of mineral and gem mines,
stone quarries, timber that has reached an age where it could be harvested, and agricultural
products that do not need a physical storage facility such as hay.
Electrochemistry In electrochemistry, the phrase in situ refers
to performing electrochemical experiments under operating conditions of the electrochemical
cell, i.e., 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.
Environmental remediation 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.
Experimental physics In experimental physics "in situ" typically
refers to a method of data collection or manipulation of a sample without exposure to an external
environment.
For example, the Si(111) 7x7 surface reconstruction is visible using a scanning tunneling microscope
when it is prepared and analyzed in situ.
Experimental psychology In psychology experiments, in situ typically
refers to those experiments done in a field setting as opposed to a laboratory setting.
Gastronomy In gastronomy, "in situ" refers to the art
of cooking with the different resources that are available on the site of the event.
Here you are not going to the restaurant, but the restaurant comes to your home.
Law In legal contexts, 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.
In the field of recognition of governments under public international law the term in
situ is used to distinguish between an exiled government and a government with effective
control over the territory, i.e. the government in situ.
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?"
with what in the same position in the sentence as the grammatical object would be in its
affirmative counterpart.
An example of an English wh-element that is not in situ: "What did John buy?"
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.
Medicine In oncology: for a carcinoma, in situ means
that malignant cells are present as a tumor but have not metastasized, or invaded, beyond
the basement membrane of where the tumor was discovered.
This can happen anywhere in the body, such as the skin, breast tissue, or lung.
This type of tumor can often, depending on where it is located, be removed by surgery.
In anatomy: in situ refers to viewing structures as they appear in normal healthy bodies.
For example, one can open up a cadaver's abdominal cavity and view the liver in situ or one can
look at an isolated liver that has been removed from the cadaver's body.
In nursing, "in situ" describes any devices or appliances on the patient's body that remain
in their desired and optimal position.
Mining In situ leaching or in situ recovery refers
to the mining technique of injecting water underground to dissolve ore and bringing the
uranium-impregnated water to the surface for extraction.
Petroleum production In situ refers to recovery techniques which
apply heat or solvents to heavy crude oil or bitumen reservoirs beneath the earth's
crust.
There are several varieties of in situ techniques, but the ones which work best in the oil sands
use heat.
The most common type of in situ petroleum production is referred to as SAGD this is
becoming very popular in the Alberta Oil Sands.
RF transmission In radio frequency 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".
Space-related 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.
The Mars Direct mission concept is based primarily on the in situ fuel production using Sabatier
reaction.
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.
Vacuum technology In vacuum technology, in situ baking refers
to heating parts of the vacuum system while they are under vacuum in order to drive off
volatile substances that may be absorbed or adsorbed on the walls so they cannot cause
outgassing.
See also carcinoma in situ
ex vivo in silico
in utero in vitro
in vivo In situ conservation
Ex situ conservation List of Latin phrases
List of colossal sculpture in situ References