Using geobrowsers for thematic mapping Bjørn Sandvik MSc in Geographical Information Science University of Edinburgh Postgraduate Research Conference 17-19 March 2008 Supervisors: Bruce Gittings and James Reid

Research questions What are the current capabilities for thematic mapping in geobrowsers? How could thematic mapping be better supported by geobrowsers? GIS & Web standards Thematic mapping Geo- browsers Public datasets Visualisations

What are the current capabilities for thematic mapping in geobrowsers?

How could thematic mapping be better supported by geobrowsers?

What are thematic maps? Choropleth maps Proportional symbol maps Graph symbol maps Animated maps (temporal) Flow maps Dot maps Isarithmic maps Dasymetric maps Cartograms Univariate maps (1) Bivariate maps (2) Multivariate maps (3+)

Choropleth maps

Proportional symbol maps

Graph symbol maps

Animated maps (temporal)

Flow maps

Dot maps

Isarithmic maps

Dasymetric maps

Cartograms

What is a geobrowser? Google Earth Google Maps OpenLayers Microsoft Virtual Earth ArcGIS Explorer NASA World Wind Yahoo! Maps 3D vs. 2D

Google Earth

Google Maps

OpenLayers

Microsoft Virtual Earth

ArcGIS Explorer

NASA World Wind

Yahoo! Maps

3D vs. 2D

Why use geobrowsers for thematic mapping? Easy to use Embeddable Support both raster and vectors Can combine dataset from various sources Sperical projection (3D) ” Earth feeling” Free Why not? To much information? Technical restrictions? Lack of OGC standards support? Ad intrusion?

Easy to use

Embeddable

Support both raster and vectors

Can combine dataset from various sources

Sperical projection (3D)

” Earth feeling”

Free

Why not?

To much information?

Technical restrictions?

Lack of OGC standards support?

Ad intrusion?

Thematic Mapping Engine Thematic Mapping Parameters OpenLayers PHP Library Web Interface Web Processing Service Thematic Mapping Engine

Choropleth map in Google Earth $map = new ThematicMap(); $map->setType("choropleth"); $map->addData($values); $map->addBorders($borders); $map->setColourRange($colors); $kml = $map->getKML(); Data source: UNdata

Using the 3rd dimension $kml = $map->getKML(‘3D’); Data source: UNdata

Proportional symbol maps $map->setType(“symbol"); $map->setBasenam($basemap); $map->setSymbolSize(”pop”); Data source: UNdata and Tom Patterson

Challenge 1: polygon holes Data source: UNdata

Challenge 2: Mercator Can OpenLayers do better?

Challenge 3: Performance

Challenge 4: Complexity function kmlSymbolCalculator( $longitude, $latitude, $distance, $points, $altitude ) { $EARTH_RADIUS_EQUATOR = 6378140.0; $RADIAN = 180 / pi(); $long = $longitude; $lat = $latitude; $long = $long / $RADIAN; $lat = $lat / $RADIAN; $f = 1/298.257; $e = 0.08181922; $kml = '<Polygon>' . PHP_EOL . ' <outerBoundaryIs>' . PHP_EOL . ' <LinearRing>' . PHP_EOL . ' <coordinates>'; for ( $bearing = 0; $bearing <= 360; $bearing += 360/$points) { $b = $bearing / $RADIAN; $R = $EARTH_RADIUS_EQUATOR * (1 - $e * $e) / pow( (1 - $e*$e * pow(sin($lat),2)), 1.5); $psi = $distance/$R; $phi = pi()/2 - $lat; $arccos = cos($psi) * cos($phi) + sin($psi) * sin($phi) * cos($b); $latA = (pi()/2 - acos($arccos)) * $RADIAN; $arcsin = sin($b) * sin($psi) / sin($phi); $longA = ($long - asin($arcsin)) * $RADIAN; $kml .= &quot; &quot;.$longA.&quot;,&quot;.$latA; } $kml .= ' </coordinates>' . PHP_EOL . ' </LinearRing>' . PHP_EOL . ' </outerBoundaryIs>' . PHP_EOL; return $kml; }

Challenge 5: Temporality

Best to follow standards? Thematic Mapping Engine DDI/DCMI SDMX Metadata ISO 19115:2003 OGC SLD/SE extension? Best practices Thematic mapping techniques GML / WFS WKT / WKB GeoJSON XML CSV Array JSON TMS Parameters Storage Data in Data out Geobrowser WMS Map Tiles KML WFS / GML GeoJSON GeoRSS

Open philosophies Open Source Open Data Open Access My sins Access for all Redistribution Vectors… Saved by UNdata… “ All data and metadata provided on UNdata’s website are available free of charge and may be copied freely , duplicated and further distributed provided that they are not put up for sale or otherwise commercially exploited and that UNdata is cited as the reference.”

Open Source

Open Data

Open Access

My sins

Access for all

Redistribution

Vectors…

Saved by UNdata…

GIS democratisation “ Central control of computer databases, such as GIS, tend to increase the power to the bureaucrats, administrators, technical experts and computer literate groups who use them at the expense of those who lack the expertise to access to these systems” (Arnoff, 1989, p. 285) “ Those with best access to knowledge and efficient information processing gain economic, military and political advantage over those lagging it.” (Onsrud, 1985)

“ Central control of computer databases, such as GIS, tend to increase the power to the bureaucrats, administrators, technical experts and computer literate groups who use them at the expense of those who lack the expertise to access to these systems” (Arnoff, 1989, p. 285)

“ Those with best access to knowledge and efficient information processing gain economic, military and political advantage over those lagging it.” (Onsrud, 1985)

Exploratory mapping ” Mapping should proceed through multiple, competing visualisations which are not created by the cartographer and transmitted to the user, but made on the spot by the user acting as his or her own cartographer” - Jeremy Cramption My dissertation: Give the data, the cartographic toolbox and the visualisation tools to the user in a web-based interface.

” Mapping should proceed through multiple, competing visualisations which are not created by the cartographer and transmitted to the user, but made on the spot by the user acting as his or her own cartographer” - Jeremy Cramption

My dissertation: Give the data, the cartographic toolbox and the visualisation tools to the user in a web-based interface.

Website and blog thematicmapping.org