In situ

Not to be confused with Insitu, Inc..

In situ is a Latin phrase meaning "in place" or "on site", derived from in ("in") and situ (ablative of situs, "place"). It refers to an object existing, or an event or process occurring, within its original environment. The term is widely used across multiple disciplines. By maintaining objects—or observing phenomena—within their original environment, in situ methods enhance analytical accuracy, particularly when contextual factors are critical to the subject under investigation. In contrast, ex situ methods involve relocating these elements, which can potentially alter or disrupt their inherent context.

In natural sciences, for example, geology and environmental science rely on in situ processes and measurements conducted directly at the site of interest. Geologists analyze soil composition and rock formations in the field to obtain accurate data unaffected by changes that might occur during transportation. Environmental scientists monitor ecosystems on-site to assess factors like pollution levels or biodiversity, ensuring that their observations reflect the true state of the environment. In biology, studying organisms in situ involves observing them within their natural habitats, essential for understanding behaviors, interactions, and ecological relationships that may not manifest under artificial conditions. Chemistry and experimental physics employ in situ methods to examine substances and reactions in their original states, allowing for real-time observation of dynamic processes.

In applied sciences, aerospace engineering utilizes in situ inspection and monitoring technologies to assess the condition of systems and components within their operational environments. Medicine, especially oncology, uses the term in situ to describe early-stage cancers confined to their original location, such as carcinoma in situ (CIS). Identifying a tumor as in situ indicates that it has not invaded neighboring tissues, which is a critical factor in determining prognosis and treatment strategies. In space science, in situ planetary exploration involves direct observation and data collection from celestial bodies without returning samples to Earth. Instruments such as Mars rovers analyze Martian soil in situ, circumventing the logistical challenges of sample-return missions while delivering the required scientific data.

In the humanities, particularly archaeology, the concept of in situ is applied to preserve the contextual integrity of the subject under examination. Archaeologists study items at their original discovery sites to maintain the spatial relationships and environmental factors that contribute to accurate historical interpretations. The arts embrace the in situ concept when creating or displaying artwork within its intended context. For example, artists may design pieces specifically for certain locations, such as sculptures integrated into public parks or installations that interact with architectural spaces. Displaying art in situ strengthens the connection between the work and its surroundings by situating the piece within a broader environmental or cultural framework.

Aerospace engineering

In the aerospace industry, in situ refers to inspection and monitoring technologies used to assess the condition of systems or components within their operational environment, without requiring disassembly or removal from service. Various non-destructive and structural monitoring methods are available for detecting in situ damage during service, including infrared thermography, speckle shearing interferometry (also known as shearography), and ultrasonic testing, which are used to characterize damage from impacts on composite structures. Each method has its limitations—infrared thermography may be less effective on materials with low emissivity, shearography requires controlled environmental conditions, and ultrasonic testing can be time-consuming for large structures. However, their combined use has proven effective in damage assessment. A study demonstrated the use of live monitoring with AC and DC sensors to identify cracks, delaminations, and fiber fractures in composite laminates by detecting changes in electrical resistance and capacitance.

Archaeology

A Hohokam arrowhead in situ

In archaeology, in situ refers to artifacts or other materials that remain at their original site, undisturbed since they were left by past peoples. Documenting the precise location, depth, and surrounding materials of in situ finds allows archaeologists to reconstruct detailed accounts of historical events and practices. While artifacts are often carefully extracted for analysis, features—such as hearths, postholes, and building foundations—typically must be documented in situ to preserve contextual information as excavation progresses to deeper layers. The documentation process includes not only written descriptions in site notebooks but also scaled drawings, mapping, and high-resolution photography. Advanced techniques such as 3D scanning and Geographic Information Systems (GIS) are employed to capture more complex details. Artifacts found out of context (ex situ) lack their original interpretive value; however, they can still offer insights into the types and locations of undiscovered in situ artifacts, thereby informing future excavations.

In the case of underwater shipwrecks, the Convention on the Protection of the Underwater Cultural Heritage articulates principles that signatory states are required to follow. Among these is the recommendation that in situ preservation be prioritized as the preferred approach. This preference partly arises from the unique preservation conditions underwater, where reduced oxygen levels and stable temperatures can keep artifacts intact for extended periods. Removing shipwrecks from their submerged context can lead to rapid deterioration upon exposure to air, such as the oxidization of iron components.

During the excavation of burial sites or surface deposits, in situ specifically refers to the detailed recording and cataloging of human remains as found in their original positions. The excavation of mass graves, in particular, shows the complexity of preserving remains in their in situ state, where they may be entangled with soil, clothing, and other artifacts. With dozens or even hundreds of bodies to recover, researchers need to document the remains in their original context before determining details such as identity, cause of death, and other forensic factors.

Art

Further information: Site-specific art

Many temporary installations by Christo and Jeanne-Claude, such as The London Mastaba (pictured), exemplify the in situ approach in art.

In the arts, the term in situ was embraced by artists and critics in the late 1960s and 1970s to describe artworks created specifically for particular locations. These works are designed with careful consideration of the site's contextual attributes, making the relationship between the artwork and its environment central to their impact. Unlike pieces that are merely placed in a location, in situ artworks are conceived in dialogue with their settings, engaging with the location's history, geography, and social functions.

This approach is exemplified in the works of Christo and Jeanne-Claude, artists known for their site-specific environmental installations. Many of their projects involved wrapping large-scale landmarks and natural features in fabric, creating temporary transformations of familiar spaces that invite viewers to reconsider their surroundings in unexpected ways—The Pont Neuf Wrapped (1985) and Wrapped Reichstag (1995) are emblematic of the in situ approach. Similarly, American land artists, such as Robert Smithson and Michael Heizer, extended this concept into the natural landscape, where the art became inseparable from the earth itself. In a broader context, in situ has become an essential term in aesthetics and art criticism, signifying an artistic strategy that emphasizes the inseparability of a work from its site.

Astronomy

A fraction of the globular star clusters in the Milky Way 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.

In astronomy, in situ also refers to in situ planet formation, in which planets are hypothesized to have formed at the orbital distance they are currently observed rather than to have migrated from a different orbit (referred to as ex situ formation).

Biology and biomedical engineering

Live sea snail, species Nataea, photographed in situ

In biology and biomedical engineering, in situ means to examine the phenomenon exactly in place where it occurs (i.e., without moving it to some special medium).

In the case of observations or photographs of living animals, it means that the organism was observed (and photographed) in the wild, exactly as it was found and exactly where it was found. This means it was not taken out of the area. The organism had not been moved to another (perhaps more convenient) 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 (a common scenario for in vitro experiments). For instance, an example of biomedical engineering in situ involves the procedures to directly create an implant from a patient's own tissue within the confines of the Operating Room.

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 original 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" (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 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 biomedical engineering, protein nanogels made by the in situ polymerization method provide a versatile platform for storage and release of therapeutic proteins. It has tremendous applications for cancer treatment, vaccination, diagnosis, regenerative medicine, and therapies for loss-of-function genetic diseases.

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.

Civil engineering

In architecture and building, in situ refers to construction which is carried out at the building site using raw materials - as opposed to 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 cast in situ (also "cast-in-place") 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 on labour costs, 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 (filled) during construction. The differences in the soil properties for supporting building loads, accepting underground utilities, and infiltrating 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.

Another use of the term in-situ that appears in Computer Science focuses primarily on the use of technology and user interfaces to provide continuous access to situationally relevant information in various locations and contexts. Examples include athletes viewing biometric data on smartwatches to improve their performance, a presenter looking at tips on a smart glass to reduce their speaking rate during a speech, or technicians receiving online and stepwise instructions for repairing an engine.

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 ---except for space for recursive calls on the "call stack." Typically such an algorithm operates on data objects directly in place rather than making copies of them.

For example, heapsort is an in situ sorting algorithm, which sorts the elements of an array in place. Quicksort is an in situ sorting algorithm, but in the worst case it requires linear space on the call stack (this can be reduced to log space). Merge sort is generally not written as an in situ 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 the image to be edited without launching a separate image editor, this is called in situ editing.

AJAX partial page data updates is another example of in situ in a Web UI/UX context. Web 2.0 included AJAX and the concept of asynchronous requests to servers to replace a portion of a web page with new data, without reloading the entire page, as the early HTML model dictated. Arguably, all asynchronous data transfers or any background task is in situ as the normal state is normally unaware of background tasks, usually notified on completion by a callback mechanism.

With big data, 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. This is also known as in-situ processing.

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, ocean 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 oceanography and ocean sciences, in situ generally refers to observational methods made by obtaining direct samples of the ocean state, such as that obtained by shipboard surveying using a lowered CTD rosette that directly measure ocean salinity, temperature, pressure and other biogeochemical quantities like dissolved oxygen. Historically a reversing thermometer would be used to record the ocean temperature at a particular depth and a Niskin or Nansen bottle used to capture and bring water samples back to the ocean surface for further analysis of the physical, chemical or biological composition.

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 stimulating the natural processes in the soil, contrary to ex situ where contaminated soil is excavated and cleaned elsewhere, off site.

Experimental physics

Main article: In situ electron microscopy

In transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), in situ refers to the observation of materials as they are exposed to external stimuli within the microscope, under conditions that mimic their natural environments. This enables real-time observation of material behavior at the nanoscale. External stimuli in in situ TEM/STEM experiments include mechanical loading and pressure, temperature changes, electrical currents (biasing), radiation, and environmental factors—such as exposure to gas, liquid, and magnetic field—or any combination of these. These conditions allow researchers to study atomic-level processes such as phase transformations, chemical reactions, or mechanical deformations, providing insights into material behavior and properties essential for advancements in materials science.

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 at the site of the event. Here a person is not going to the restaurant, but the restaurant comes to the person's 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 (for example, "John bought bread"). An example of an English wh-element that is not in situ (see wh-movement): "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

Diagram of an in situ carcinoma, not having invaded beyond the basement membrane

In cancer/oncology: in situ means that malignant cells are present as a tumor but have not metastasized, or invaded beyond the layer or tissue type where it arose. This can happen anywhere in the body, such as the skin, breast tissue, or lung. For example, a cancer of epithelial origin with such features is called carcinoma in situ, and is defined as not having invaded beyond the basement membrane.

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.

In medical simulation, "in situ" refers to the practice of clinical professionals using high fidelity patient simulators to train for clinical practice in patient care environments, such as wards, operating rooms, and other settings, rather than in dedicated simulation training facilities.

In biomedical, protein nanogels made by the in situ polymerization method provide a versatile platform for storage and release of therapeutic proteins. It has tremendous applications for cancer treatment, vaccination, diagnosis, regenerative medicine, and therapies for loss-of-function genetic diseases.

Mining

In situ leaching or in situ recovery refers to the mining technique of injecting lixiviant underground to dissolve ore and bringing the pregnant leach solution to surface for extraction. Commonly used in uranium mining but has also been used for copper mining.

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 (steam).

The most common type of in situ petroleum production is referred to as SAGD (steam-assisted gravity drainage) this is becoming very popular in the Alberta Oil Sands.

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 air."

Space science

Main article: In situ resource utilization

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 the Sabatier reaction, which produces methane and water from a reaction of hydrogen and carbon dioxide.

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.

Urban planning

In urban planning, in-situ upgrading is an approach to and method of upgrading informal settlements.

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.

Road assistance

The term in situ, used as "repair in situ", means to repair a vehicle at the place where it has a breakdown.

See also

• In situ conservation
• Ex situ conservation
• List of colossal sculptures in situ
• List of Latin phrases
• All pages with titles beginning with In situ