In situ tests* are, literally, those that are carried out in the same place where the object of analysis is located. In geotechnics, the term is applied to the tests that are carried out on land to determine its characteristics. In construction it is usually used to define the testing of materials on site, especially in the foundation elements. On-site tests are also carried out in other fields, such as environment (noise measurements, pollution, mainly), agriculture, etc.

They are part of the geotechnical recognition techniques, constituting an alternative or complement to laboratory tests on extracted samples.

They aim to eliminate or reduce some of the limitations of laboratory tests:

The extracted samples are small in size, so they are only representative of a small portion of the land. This drawback is solved by taking a large number of samples. However, in many cases the behavior of the terrain cannot be modeled based on small-size measurements. This occurs when there are macrostructural features such as the presence of bowls or edges, jointing, cracking, stratification or schistosity in residual soils and rocks, distribution of lenses, variations in depth, etc.

"In situ" tests allow, in principle, to obviate these limitations. However, this is only partially achieved, and on the other hand, new ones appear:

There is a wide variety of in situ tests, which can be grouped according to various criteria:

On the other hand, in situ tests also differ from each other in terms of their purpose, which ranges from general recognition for identification of soil types, to complex and expensive tests on foundation elements that require large resources for their execution.

Geophysical methods and penetration tests could be considered included within the group of in situ tests. However, they have particular characteristics, and constitute in themselves important elements in the recognition of the terrain.

The main types of in situ tests on land are: