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Authored by Fabian Kowatsch

FOSS4G 2019 Lab Example 1: Visualizing the evolution of buildings of the inner city of Bucharest


Full lab presentation: 2019-08-28_foss4g_lab.pdf


Software Requirements:

Estimated Time:

  • 20 minutes (variable depending on size of data and resolution of GIF)

This example explains how to generate a time series visualization of the evolution of buildings within a defined bounding box (in this case, the inner city of Bucharest). It consists of three main steps that are as follows:

Step 1: data extraction using the ohsome API

We define the parameters that we want to use as a filter for our request:

bbox: 26.0785,44.422,26.12173,44.44078 generated using http://norbertrenner.de/osm/bbox.html
time: 2008-01-01 until 2019-07-01
keys: building
types: way,relation
properties: metadata,tags (so we also get all the tags of each OSM feature)

full URL:
https://api.ohsome.org/v0.9/elementsFullHistory/geometry?bboxes=26.0785,44.422,26.12173,44.44078&keys=building&properties=tags,metadata&showMetadata=yes&time=2008-01-01%2C2019-07-01&types=way,relation

response:
buildings_way-relation.geojson

Step 2: importing and preparing the GeoJSON data in QGIS

drag-drop the GeoJSON into QGIS
choose polygons only
save the layer as geopackage
define a styling of the data, e.g. using the @version attribute

Step 3: creating a time series visualization using TimeManager plugin + ImageMagick

load data into TimeManager and define start+end times using @validFrom and @validTo attributes
export the video as .png files (Windows) or directly as animated gif or video (Linux, OSX)
Windows: create a gif using tool like ImageMagick

ImageMagick command:
magick convert -resize 1024x768 -delay 10 -loop 0 *.png result.gif


Further info: http://k1z.blog.uni-heidelberg.de/?s=ohsome
Link to example 2: https://gitlab.gistools.geog.uni-heidelberg.de/snippets/24

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