Abstract <p>The achievements and problems of V.B. Sochava’s geosystem doctrine, its spread abroad, and development towards the joint use of conceptual, statistical, and mathematical analysis in geography are discussed. The doctrine is considered in the context of the general systems theory and the possibility of applying other intertheories that explain the properties of nature, economy, and population of a territory in unified system terms. The basic concept is a “structure” that imposes a system order on a set of elements to ensure their organization and functioning. Geosystems differ in the type of intertheoretical description of elements and their relationships—complex, functional, dynamic, behavioral, classificational, etc., as well as in the form of expression: natural and integral geosystems, metasystems, monosystems, polysystems, geocomplexes, episystems, chorions, and holosystems. Their properties are reflected by special mathematical formulas of differential geometry of layered (fibered) spaces. In particular, holosystems of integrity are described as structures of surfaces defined by continuous functions (manifolds), enveloping in these spaces the planes of functions of a set of adjacent monosystem layers (geomeres) and thereby determining their pairwise connectivity and territorial organization of polysystems (geochores) in the unity of the geographical environment. Different types of geosystems are considered only as subjects, not objects, of geographical research, which makes it possible to choose specific directions, models, and methods for solving scientific problems. The formalization of accumulated geosystem knowledge is supported by conceptual schemes in the form of graphs and charts and materials of statistical processing of primary and cartometric data. Sochava set the task of creating a functional-geomeric model to reflect the importance of geomers in the structure of geochores. It is proposed to discuss this problem in terms of the ordinal intertheory of describing the distribution of geoms by significance (occurrence) in different physical–geographical regions of Baikal Siberia. It is assumed that the same problem is solved by different intertheories using the appropriate mathematical apparatus. The development of such research tools corresponds to different ways to improve the geosystem analysis methods.</p>