The study of mathematical knowledge in different contexts has acquired relevance due to the current interest in students' ability to use mathematics in solving real life problems. Thus, the purpose of this research is to characterize the knowledge in use in the measurement of inaccessible distances in Johann Stoffler's Elucidatio Fabricoe Ususque Astrolabii, published in 1513. The theoretical model used considers the study of the constitution of knowledge through the analysis of its genesis, development and transversality. The results reveal in the analyzed work an episteme of the measurement of inaccessible distances that includes both the search for a suitable reason to carry out the measurement and the dynamic analysis of the behavior of the shadows or the visual rays in the estimation of inclinations. This episteme is critical for the understanding of this mathematical knowledge in problem solving.