Capsule Robot Endoscope (CRE), as one of the widely used methods of gastrointestinal medical examination, has the characteristics of painless, non-cross infection, and no movement restriction, compared with other traditional endoscopes. To obtain the precise location of the lesion, positioning the capsule robot in the digestive tract has become a hot research topic in related fields. In recent decades, with the rapid advancement of indoor and outdoor positioning technologies, several well-established methods have emerged that enable the acquisition of high-precision real-time spatiotemporal integration data. These methods hold great potential for interdisciplinary applications in location services across various domains. The manuscript aims to draw inspiration from surveying and mapping positioning techniques by reviewing existing microspace positioning technologies to overcome inherent technical challenges. This article has reviewed more than 100 pieces of literature at home and abroad from four major academic search engines and has further studied the state of the art of several capsule robot positioning technologies commonly used. Microspace positioning technology in capsule robots is evaluated across eight factors: positioning accuracy, power consumption, portability, comfort, complexity, robustness, extensibility, and cost. We summarize the technical challenges associated with capsule robot positioning technology from each positioning technology's limitations, finally proffering prospective avenues for future research. Our investigation reveals that the six identified capsule robot positioning technologies have distinct advantages and disadvantages. Among these, magnetic field-based positioning technology exhibited superior overall performance and is gradually advancing toward commercialization. Vision-based positioning technology, while significantly contributing to medical applications, particularly in enhancing augmented reality and surgical navigation, faces challenges related to the weak-textured and non-rigid characteristics of the gastrointestinal environment. Additionally, the limitation posed by the size and energy consumption of capsule robots make difficulties for single-source positioning techniques. We have proposed several promising future research directions by considering the capsule robot's current positioning technological challenges and the advancements of cutting-edge indoor and outdoor positioning technologies. These include exploring new positioning sources, integrating multiple sensor fusion, and developing real-time three-dimensional gastrointestinal models. These new approaches are expected to enhance the safety and reliability of capsule robot positioning technology. They can potentially promote the development of capsule robots further and provide support for diagnosing and treating gastrointestinal diseases.
