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M apping technique s Symbol and dot maps

Explore the use of symbol and dot maps to represent numerical data on point locations accurately. Understand geometric and pictographic symbols, scaling methods, and the application of dot maps for spatial data visualization. Contact Diana Makarenko-Piirsalu for more information.

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M apping technique s Symbol and dot maps

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  1. Mapping techniquesSymbol and dot maps Mrs Diana Makarenko-Piirsalu MSc in Landscape Ecology and Environmental Protection Geolytics OÜ Mere tee 15, Saviranna, Jõelähtmevald, Harjumaa, ESTONIA diana.makarenko-piirsalu@geolytics.ee Mob. +372 556 19 636 ESTP Course: Use of GIS in NSIs – Representing statistics on thematic maps, Kongsvinger,Norway, 5th to 37th of March, 2013 Attribution (by) Licensees may copy, distribute, display and perform the work and make derivative works based on it only if they give the author or licensor the credits in the manner specified by these. http://creativecommons.org/licenses/by/3.0/

  2. What are symbol maps? • Used to represent numerical data on point locations • True point data • Measured at actual point locations (persons crossing border at border guard locations) • Raw data are used • Conceptual point data • Data are collected over areas but represented at point locations ( number of inhabitants in a city) • Standardized data can be used ( the same standardization methods are applicable as for choropleth maps: ratio of two raw attributes)

  3. Symbols • Geometric symbols • Visually more stable (circles) • More difficult to estimate relative size of 3D symbols • Pictographic symbols • Facilitate understanding of phenomena • In case of overlapping difficult to interpret • More difficult to estimate the relative size Source: Statistical atlas of Lithuania 2010, Statistics Lithuania, 2010

  4. Scaling proportional symbols • Mathematical scaling • Symbol sizes are represented in direct proportion to corresponding data value • Perceptual scaling • Larger symbols are made visually larger as people eyes tend to underestimate the size of large symbols relation to actual data value • Range - graded scaling • Based on the classed data each class will be represented with different size of the symbol • Size for symbols are determined to represent the class values visually logically

  5. Dot maps • Used to represent numerical data • Conceptual data can be used (number of persons in administrative units, inhabited areas) • Determine areas into which dots should be placed based on the spatial distribution of the phenomena and available data • Select dot size (how big the dot is) and unit value (how much the dot represents) • Dot size – too small „insignificant“ distribution vs too high „excessive density“ • In the area with the highest density of the phenomena dots should start almost merge with each other

  6. THANK YOU! Mrs Diana Makarenko-Piirsalu MSc in Landscape Ecology and Environmental Protection Geolytics OÜ Mere tee 15, Saviranna, Jõelähtmevald, Harjumaa, ESTONIA diana.makarenko-piirsalu@geolytics.ee Mob. +372 556 19 636 ESTP Course: Use of GIS in NSIs – Representing statistics on thematic maps, Kongsvinger,Norway, 5th to 7th of March, 2013

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