In the study, the latest computer methods of clustering and visualization are applied to reliable and quantitatively relevant intralinguistic and extralinguistic data on adjacent crossborder dialects of two closely related South Slavic languages, Serbian and Bulgarian, for the first time in Slavic linguistic geography. The survey is a pilot experimental one. The objectives of the study are the correct machine conversion of the existing analog primary data into a digital format, the development of digital tools for processing and clustering the primary data, and the generation of trial combinatorial linguistic maps. It is assumed that as a result of applying the methods of systematization, analysis, synthesis, and visualization of the geographical distribution of clusters of linguistic and extralinguistic data, a cartographic explication of objective boundaries between closely related languages is possible. The primary data for the study were obtained by a machine digitizing of a part of the South Slavic diale