The third Wednesday of each November is GIS Day! Arnaud started us off with a gereral presentation about GIS in French. - GIS are systems for representing spatial and geographic data: vector and raster, capable of loading many geographic filetypes, and projecting these data onto a 2d plane (the screen). - We got sidetracked by important discussions about Null Island (lat 0°, long 0°) which can become a graveyard for geocoding errors… see the wikipedia article - Inventory of different GIS software, with a nod to the goal of tonight’s presentation: QGIS
Adam then led us through two tutorial from qgistutorials.com. After downloading and installing QGIS, we dove into the first tutorial: 1) Working with attributes The goal was to work with the data in order to find cities with more than 1 million inhabitants, which were also capital cities. We did this by creating attribute selections, and also by querying the data source. Workshop successfully completed by all participants!
On to the next: 2) point in polygon Here we wanted to associate earthquake data to the country in which the earthquake occured, in order to ascertain the country with the most significant earthquakes. We added on to the workshop by symbolising each polygon in the output dataset by the number of recorded significant earthquakes, as determined in our analysis. Again, workshop successfully completed by all participants!
We then checked out a QGIS plugin (OpenLayers Plugin) to enable OSM basemaps in QGIS, which gives us instant reference for our data.
A few interesting links: dropchop.io super lightweight GIS client, thetruesize.com view how the Google mercator projection can be misleading, Jason Davies’ Projection transitions, and finally qgis.org.
Next meetup scheduled - Tuesday 15 December for another leaflet.js tutorial.
Thanks again to our organisers for sharing their knowledge in a kind manner!
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22 Décembre 2015
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