Each year, new localisation techniques elaborate new potential objectives. In recent years they have been trying to accost the hidden part of the localisation systems. In fact, each technique deployed outdoors, cannot easily be deployed indoors or when we have an environment with difficulties. This phenomenon is due to the large number of obstacles that a transmitted signal has to pass, as in the case of GPS systems. The scientific world has carried out research to improve indoor methods, using different techniques. In the following article, we describe some of these techniques and try to understand their functionalities, study the advantages, the drawbacks, and make comparisons. The real aim of this paper is to create a quasi-exhaustive list of the existing methods to localize or position a mobile device, in extremely difficult conditions. To obtain the final position, systems use data that they compute with mathematical equations by different ways. In general, they use the distances or angles between a mobile and reference points or bases. These data are employed to reach the outcome