Geog 380: Geospatial Communication Mapping Techniques PDF
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Uploaded by HotInfinity5397
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2023
Geoffrey Hay
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Summary
These lecture notes cover mapping techniques, including types of maps, symbols, and spatial data representation. The notes also discuss choropleth maps, proportional symbol maps, dot maps, heat maps, and dasymetric maps. The focus of the lecture revolves around the methods used in cartography.
Full Transcript
Geog 380: Source: https://earth.nullschool.net Geospatial Communication Topic 04: Mapping Techniques © Geoffrey Hay (2023) Next few topics Topic 04: Topic 05: Topic 06: Map types/techniques Data measurement and classification Colour and Symbology GEOG 380 (Topic 04) 2 Learning outcome...
Geog 380: Source: https://earth.nullschool.net Geospatial Communication Topic 04: Mapping Techniques © Geoffrey Hay (2023) Next few topics Topic 04: Topic 05: Topic 06: Map types/techniques Data measurement and classification Colour and Symbology GEOG 380 (Topic 04) 2 Learning outcomes By the end of this lecture topic, a successful student will be able to: § Identify some of the main map types and techniques § Evaluate different techniques for types of spatial data GEOG 380 (Topic 04) 3 Types of maps https://ftp.maps.canada.ca/pub/nrcan_rncan/raster/atlas/eng/reference/n_america/mcr_0031_2005.jpg § Reference vs. thematic § Static vs. dynamic § Geovisualization is equivalent to “interactive digital cartography” § Interesting examples: World City Populations The Carbon Map Johns Hopkins Covid-19 World – wind, air, and water GEOG 380 (Topic 04) 4 Functions of symbols Differentiate between ‘things’ Convey quantity Indicate location Encloses (e.g., surrounds) to create structure Highlight or draw attention to a particular ‘thing’ Form meaning – symbols encoded to contain data/info § Symbols can be Field 2018; Pg. 459 § § § § § § https://www.educare.bz/unit/ the-concept-of-map-symbols/ § Geometric § Mimetic (i.e., resemble or imitate) § Literal § Symbols derived from the abbreviation of some words – in the form of text/letters. Used to indicate the locations of features they represent GEOG 380 (Topic 04) 5 Feature dimensionality § Point – 0-D § Has location – is infinitely small § Line: 1-D § Has length § Polygon/region/area: 2-D § Has length and width https://www.slideshare.net/iivanoo/mission-planning-of-autonomous-quadrotors § ‘Functional surface’: 2.5-D § Continuous surface which can have only one z-value of an attribute for any x, y location (e.g., elevation) § Volumes: 3-D § Can have multiple values of attribute at each x,y location § Or, in other words, has an attribute for each x,y,z location GEOG 380 (Topic 04) 6 Nature of spatial data Field 2018; Pg. 99 GEOG 380 (Topic 04) 7 Choropleth maps § Commonly use to portray data collected from discrete spatial units § i.e., municipalities or provinces § A (statistical thematic) shaded map based on a range of values in the key i.e., age, wealth, population. § Limitations https://upload.wikimedia.org/wikipedia/commons/1/17/World_population_density_map.png § (Example) The Carbon Map GEOG 380 (Topic 04) § Does not show variation within the unit § Boundaries are arbitrary – not necessarily associated with discontinuities in phenomenon 8 Class # & colors § What colors should you use and how many classes? § ColorBrewer 2.0 https://colorbrewer2.org/ type=sequential&scheme=BuGn&n=3 GEOG 380 (Topic 04) 9 Choropleth – issues (e.g., MAUP) § The Modifiable Areal Unit Problem (MAUP) occurs by aggregating data and representing it with bias at different scales or boundary extents. https://gis.blog.ryerson.ca/2020/03/26/the-graduated-colour-map-a-minefield-for-armchair-cartographers/ GEOG 380 (Topic 04) https://www.canadiangeographic.ca/article/what-are-maps-really-saying-about-covid-19-canada 10 Proportional symbol maps § Scaling of symbols in proportion with a magnitude in the data § One of the biggest challenges is how to scale the symbol? § Extreme values dominate (or small ones are invisible) § Balance between readability and clutter https://en.wikipedia.org/wiki/Proportional_symbol_map#/media/File:Europe_GDP_Map.png GEOG 380 (Topic 04) 11 http://gisandstuff.blogspot.com/2015/02/choropleth-and-proportional-symbol.html Proportional symbol and choropleth GEOG 380 (Topic 04) 12 Dot, heat maps and dasymetric maps § Dot maps § Each dot represents a count of things § Placement of dots § Heatmaps § Show the density of dots not the dots themselves § Dasymetric https://i.redd.it/26g2wrtp7p871.png § Analogous to choropleth but doesn’t follow enumeration unit such as a postal code/census area (as these are somewhat arbitrary units). § Often used for population density GEOG 380 (Topic 04) 13 Dot & Heatmaps https://www.esri.com/arcgis-blog/products/js-api-arcgis/mapping/interactive-dot-density-maps-for-the-web/ GEOG 380 (Topic 04) https://developers.arcgis.com/javascript/latest/api-reference/esri-renderers-HeatmapRenderer.html 14 Dasymetric Map § Dasymetric mapping technique is one potential solution for mapping population density relative to residential land-use. § Dasymetric mapping depicts quantitative areal data using boundaries that divide the area into zones of relative homogeneity with the purpose of better portraying the population distribution. § Choropleth vs Dasymetric https://www.sfu.ca/geog/geog452spring03/group1/ choropleth.html Comparison of a choropleth map (top) and a dasymetric map (bottom) GEOG 380 (Topic 04) https://commons.wikimedia.org/wiki/File:DasymapBG_Bay_Area_choropleth_and_dasymetric_maps.jpg 15 Isarithmic mapping Based on the concept of continuity of phenomena § It is a 2D representation of a 3D volume Ø 2 Types of isarithmic maps exist: 1. Isometric § § True point data 2. Isopleth Field 2018; Pg. 245 § Conceptual point data § Collected over a geographical area or volume but data is considered located at points § Purpose to show how features differ in quantity as a surface. GEOG 380 (Topic 04) https://weatherworksinc.com/news/high-low-pressure 16 Isarithmic mapping § Isolines § lines connecting data points of the same value i.e., height § § Field 2018; Pg. 245 § Shading between isolines – suggests steps Continuous tone – many colours/grey shades Fishnet or 3D perspective view – obscures part of area GEOG 380 (Topic 04) 17 Isolines https://thetopoischanging.wordpress.com/2014/05/23/climate-lingo-1-isotherms-weremoving-poleward-baby/ https://www.weatheronline.co.uk/reports/wxfacts/Isobars-on-surface-maps.htm http://mapanalysis.blogspot.com/2011/04/isohyets.htm l GEOG 380 (Topic 04) 18 Topographic/relief maps § § GEOG 380 (Topic 04) https://www.maproomblog.com/2021/09/hachure-maps-in-qgis/ Many techniques used to map other continuous phenomena relevant for topography /elevation/relief 19 Unidirectional vs multidirectional hillshades https://pro.arcgis.com/en/pro-app/latest/help/analysis/raster-functions/hillshade-function.htm GEOG 380 (Topic 04) 20 Multivariate map (emphasis is on relationships) Slocum et al. 2005; Plate 18.4 Slocum et al. 2005; Plate 18.1 Slocum et al. 2005; Plate 18.2 Slocum et al. 2005; Plate 18.3 Slocum et al. 2005; Plate 18.5 GEOG 380 (Topic 04) 21 Spatial data and cartographic technique Field 2018; Pg. 99 § Spatial data can be represented in different ways § Up to cartographer to decide which method is best for the nature of the data and the message they want to communicate GEOG 380 (Topic 04) 22