Dasymetric map

The dasymetric map is a method of thematic mapping, which uses areal symbols to spatially classify volumetric data. The method was defined and developed in 1911 by Benjamin (Veniamin) Petrovich Semenov-Tyan-Shansky[2] and popularised by J.K. Wright, although there are earlier references to similar techniques from George Poulett Scrope (1833)[2] and Henry Drury Harness (1838).[3][4]

Mapping

The term "dasymetric" was invented by Semenov-Tyan-Shansky using the Greek translation for "measuring density" (dasys – dense, metreo – to measure).[2] Semenov-Tyan-Shansky defined dasymetric maps as maps "on which population density, irrespective of any administrative boundaries, is shown as it is distributed in reality, i.e. by natural spots of concentration and rarefaction."[2]

Developed methods and approaches in dasymetric mapping include areal interpolation, filtered areal weighting using the binary method, filtering with land cover data, and cadastral-based expert dasymetric system.[5][6]

Dasymetric maps are used instead of choropleth maps because they represent underlying data distributions more accurately. Choropleth maps and dasymetric maps differ in three main ways. First, dasymetric zones are generated using ancillary data while boundaries on choropleth maps use units used for more general purposes (such as U.S. county boundaries). Second, choropleth zones have varying levels of internal homogeny while dasymetric maps are designed to be internally homogenous.[7] Last, choropleth mapping methods are standardized while dasymetric methods are under researched.[8]  

Considered a hybrid or compromise between isopleth and choropleth maps,[9][10] a dasymetric map utilizes standardized data, but places areal symbols by taking into consideration actual changing densities within the boundaries of the map. To do this, ancillary information is acquired, which means the cartographer steps statistical data according to extra information collected within the boundary.

Like other forms of thematic mapping, the dasymetric method was created and historically used because of the need for accurate visualization methods of population data. Dasymetric maps are not widely used because of a lack of standardized dasymetric mapping techniques that are accessible to the public. This leads to methods which are highly subjective with inconsistent criteria.[5] Although fields such as public health still rely on choropleth maps, dasymetric maps are becoming more prevalent in developing fields such as aerial interpolation and population estimation using remote sensing.[5]

References

  1. "Western Geographic Science Center". Retrieved 13 November 2015.
  2. Petrov, Andrey (2012). "One Hundred Years of Dasymetric Mapping: Back to the Origin". The Cartographic Journal. 49 (3): 256–264. doi:10.1179/1743277412Y.0000000001.
  3. Harness, Henry D. (1838). Atlas to Accompany the Second Report of the Railway Commissioners, Ireland. H.M.S.O., Dublin.
  4. Robinson, Arthur H. (1955). "The 1837 Maps of Henry Drury Harness" (PDF). The Geographical Journal. 121 (4). pp. 440–450.
  5. Lwin, K.K (March 2010). "Development of GIS Tool for Dasymetric Mapping". International Journal of Geoinformatics. 6: 11–18.
  6. Maantay, Juliana Astrud; Maroko, Andrew R.; Herrmann, Christopher (2007-01-01). "Mapping Population Distribution in the Urban Environment: The Cadastral-based Expert Dasymetric System (CEDS)". Cartography and Geographic Information Science. 34 (2): 77–102. doi:10.1559/152304007781002190. ISSN 1523-0406.
  7. Mennis, Jeremy (2003). [DOI: 10.1111/0033-0124.10042 "Generating Surface Models of Population Using Dasymetric Mapping"] Check |url= value (help). The Professional Geographer. 55: 31–42.
  8. Eicher, Cory L. (2001). [10.1559/152304001782173727 "Dasymetric mapping and areal interpolation: Implementation and evaluation"] Check |url= value (help). Cartography and Geographic Information Science. 28: 125–138.
  9. "Dasymetric Mapping and Areal Interpolation: Implementation and Evaluation. – Cartography and Geographic Information Science". Accessmylibrary.com. Retrieved 2011-12-14.
  10. http://www.geog.ucsb.edu/~kclarke/G118/Lecture08.html

Further reading

  • Petrov, A. "Setting the record straight: On the Russian origins of dasymetric mapping." Cartographica, 2008, 44(2)
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