- Tytuł:
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Sposoby ujęcia danych a poprawność map opracowanych metodą kartogramu
Data character and correctness of choropleth maps - Autorzy:
- Tomaszewska, M.
- Powiązania:
- https://bibliotekanauki.pl/articles/204173.pdf
- Data publikacji:
- 2009
- Wydawca:
- Polskie Towarzystwo Geograficzne
- Tematy:
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kartogram
dane
poprawność
mapa
choropleth map
correctness
maps - Opis:
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W artykule krytycznie podsumowano dorobek kartografii w zakresie stosowanych podziałów sposobów ujęcia danych, przedstawiono propozycję typologii danych uwzględniającą najczęściej stosowane przez kartografów kryteria i na jej tle oceniono poglądy kartografów na poprawność kartogramów w zależności od sposobu ujęcia danych wykorzystanych do ich opracowania.
Choropleth is currently one of the most commonly used methods of cartographic presentation. However, the rules of application of this method have not been clearly established yet. One of the controversial issues is the character of data. Using the criterion of presentation data can be divided into 'raw' data, not related to any other data (i.e. absolute) and data in the form of a fraction, related to other data (i.e. relative). The method of presentation also determines further divisions of relative data used in cartographic literature. Division into the two categories (absolute and relative data) is widely accepted by cartographers, but the way they interpret relative data varies. It is visible in various terminology used for relative data by particular authors and various elements that it refers to (B.D. Dent 1996; K. Kocimowski, J. Kwiatek 1976; M. Kraak, F.-J. Ormeling 1998; J. Pastawski (ed.) 2006; L. Ratajski 1973, 1989; A.H. Robinson 1953; A.H. Robinson 1995; K.A. Saliszczew 1976; Slocum et al. 2009; W. Witt 1967, E. Wonka 1979, J.K. Wright 1995).The criteria used for classification of the character of data are not sufficient for establishing a specific definitive and exclusive logical division of the character of data (W. Marciszewski 1988). The author suggests a typological approach. When determining types the author proposes to keep the division into absolute and relative data (obtained by referring one set of data to another). On the other hand one has to recognize the aspect of data processing by mathematical-statistical operations and classify them as processed and unprocessed. Using the two criteria presented above the author proposes to determine four main data types: absolute unprocessed (e.g. the number of births), absolute processed (e.g. average number of births in the years 2000-2005), relative unprocessed (e.g. relation of births to deaths), relative processed (variation of the relation of births to deaths). The above considerations concerning the typological approach to the character of data can be presented as a scheme (fig. 1). Since some data types can not be classified as either purely relative or absolute, the sets overlap (gray area). This approach creates two intermediate types: data which can be considered either absolute processed or relative unprocessed (e.g. the number of cars per family in Warsaw treated as the total number of cars related to the number of families, or as an average number of cars per family) and data which can be classified either as absolute processed or relative processed (e.g. increase of the average number of cars per family in Warsaw in the last decade). Therefore six categories can be established. Cartographers agree, that the most proper method of map elaboration using the choropleth method is the one which uses relative data applied to the entire area of enumeration units, shown on a map of e.g. population density (B.D. Dent 1996; G.F. Jenks 1976; G.F. Jenks, F.C. Caspall 1971; F.J. Monkhouse 1970; F.J. Monkhouse, H.R. Wilkinson 1971; J.-C. Muller 1983,1985; M.-J. Kraak, F. Ormeling 1998; J. Pasławski 1991, 2003; J. Pravda 1983, 2004, T.A. Slocum et al. 2009). This group of the character of data - presented on the scheme as a dense dot pattern (fig. 2) - constitutes only a part of two basie types representing relative data. Method of elaboration of a choropleth basing on such data and its correct interpretation (linked to the size of basie fields) is presented in fig. 3. For choropleth map design cartographers also accept the use of other relative data: amounts related to a part of the area of enumeration units (e.g. share of wheat sown area in the total sown area), amounts related to the total population of a unit (e.g. share of population aged 1595 in total population), amounts related to a part of the population of a unit (e.g. percentage of working individuals) and amounts referred to other elements (e.g. number of inhabitants per pharmacy), (among others: D.J. Cuff, K.R. Bieri 1979; G.F. Jenks 1976; M.-J. Kraak, F. Ormeling 1998; L. Ratajski 1989; A.H. Robinson et al. 1988, 1995; K.A. Saliszczew 2001). The group of data which the article describes as relative (related to elements other than the total area of the enumeration unit) refers to two, previously discussed basie types (blue color) and two intermediate types (gray color). Its range is shown in sparse dot pattern (fig. 2). The reader interpreting the choropleth prepared basing on the data referring to elements other than the total area of the enumeration unit should be aware that the values of the presented indicator can be unconnected to the area of those units, and that the indicator's value is also affected by the data in its denominator, though such information is often not provided (fig. 4). Most cartographers are convinced that absolute data should be presented in the form of proportional symbols. Specialist who deny the possibility of applying absolute data for preparation of choropleth maps point out interpretative difficulties resulting from different size of reference units (D.J. Cuff, K. R. Bieri 1979; B.D. Dent 1996; G.F. Jenks 1976; A.H. Robinson, R. Sale, J. Mor-rison 1988; T.A. Slocum et al. 2009). When reading a choropleth map prepared using absolute data one should overlook the size of enumeration units (fig. 5), as in the case of choropleth presentations basing on relative data (referring to other elements than the enumeration unit). It should be pointed out that in the case of such presentation the values are not affected by any other data, which makes interpretation easier. It should be reminded that some data classified as relative data can be at the same time classified as absolute data. Therefore it is difficult to accept a notion that absolute data can not be used for choropleth maps. Considering the arguments presented by cartographers and the rangę of ambiguity concerning the classification of the character of data, one should recommend the use of relative data (referring to the whole enumeration unit) for preparation of choropleth maps. However, bearing in mind how common choropleth maps are, such recommendation is unlikely to change cartographic practice. What is more, application of other than relative data (refering to the whole area) for choropleth maps may have certain advantages e.g. basing on a choropleth it is easy, on the general level of map reading, to separate regions characterized by a certain value. Further theoretical considerations concerning the correetness of choropleth maps should also account for the results of empirical research on the preferences and skills of such maps' users. - Źródło:
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Polski Przegląd Kartograficzny; 2009, T. 41, nr 3, 3; 209-220
0324-8321 - Pojawia się w:
- Polski Przegląd Kartograficzny
- Dostawca treści:
- Biblioteka Nauki
Artykuł