Hay_Geog380_Topic_04_Mapping_Techniques_v4_Weather.pdf

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