W artykule przedstawiono różne możliwości zastosowania w kartografii trójkąta Osanna, zwanego również wykresem trójkątnym. Po krótkim zarysowaniu historii tego sposobu prezentacji, szczegółowo omówiono jego właściwości oraz zasady konstrukcji. Pokazano różne sposoby czytania i interpretacji trójkąta, a także kartograficzne przykłady jego zastosowania.
EN
Osanna Triangle, also known as a triangular diagram, is a specific method of data presentation, used in statistics and socio-economic cartography to present phenomena of three-fold structure. This type of diagram presents which part of the whole is composed by particular elements, what the proportion of those elements is and how similar elements in two or more various entities compare. It is used as an independent presentation form as well as a legend of thematic maps. The term 'Osanna Triangle' comes from a name of a German mineralogist, Alfred Karl Osanna (1859-1923), who analyzed minerals according to their atomic and particle contents. The chemical classification of rocks, which he prepared, was presented on triangular diagrams. Osanna Triagle is a diagram of relations of three variables placed in a system of three coordinates. The location of each point within the triangle is determined by three coordinates, read at its sides, on heights led from its angles or on lines of the grid (fig. 2). Proper interpretation of the diagram bases on the understanding of significance of points' placement within the triangle. Often the triangle is divided into smaller units (triangles, rectangles) in order to establish areas where points with similar features occur (fig. 4). This diagram can be used to present the structure of a given statistical set and also conclusions about the whole set (fig. 5). Also, it can show the dynamics of a phenomenon through changing value of particular elements of the structure in time (fig. 6). Osanna Triangle is frequently used as an explanation, map legend, most often related to a choropleth presentation. Basing on a triangular diagram one can conclude about the distribution of phenomenon's value and determine choropleth classes. Application of an unorthodox triangular set of coordinates, to which we are not used, makes the perception of Osanna Triangle rather difficult. Perhaps this is why this method of data presentation is not commonly used.
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