page_title: Dasymetric map
section_title: History
hierarchical_section_title: Dasymetric map / History
caption_attribution_description: English: A map of population density, from an 1833 book by George Poulett Scrope on Political Economy. The cartographer is not credited. Obtained from a public domain scan at archive.org
context_page_description: The dasymetric map is a type of thematic map that uses areal symbols to visualize a geographic field by refining a choropleth map with ancillary information about the distribution of the variable.
context_section_description: The earliest maps using this kind of approach include an 1833 map of world population density by George Julius Poulett Scrope and an 1838 map of population density in Ireland by Henry Drury Harness, although the methods used to create these maps were never documented.
  The term "dasymetric" was coined in 1911 by Semenov-Tian-Shansky, who first fully developed and documented the technique, defining them 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.". He proposed several methods for improving on choropleth maps, some of which can more properly termed isarithmic maps, but the dasymetric technique he most fully developed and applied is still used today, albeit using digital data and tools such as  GIS.
  Beyond Russia, the technique was popularized in the 1930s by J.K. Wright, who has sometimes been incorrectly credited with its invention.
  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.  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.
caption: Scrope's 1833 map of world population density, possibly the first dasymetric map.
exif: {"Image Tag 0x000B": "Windows Photo Editor 10.0.10011.16384", "Image Orientation": "Horizontal (normal)", "Image Software": "Windows Photo Editor 10.0.10011.16384", "Image DateTime": "2019:12:20 15:07:14", "Image ExifOffset": "2242", "Image Padding": "[]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "96", "Thumbnail YResolution": "96", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "4516", "Thumbnail JPEGInterchangeFormatLength": "10113", "EXIF DateTimeOriginal": "2019:12:20 15:06:34", "EXIF DateTimeDigitized": "2019:12:20 15:06:34", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF ColorSpace": "sRGB", "EXIF Padding": "[]"}