Georeferencing

21.05.2017 12:31 Uhr

Georeferencing in QGIS

  • Download this file: http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~279991~90052930 in at least large size
    • Use export button
  • Open QGIS Desktop 2.18.6
  • Make sure the following plugins are installed: Erweiterungen –> Erweiterungen verwalten und installieren…
    • GDAL-Georeferenzierung
    • OpenLayers Plugin
  • Open a suitable backgound map
    • Web –> OpenLayers plugin
  • Choose Raster –> Georeferenzierung
  • Open downloaded file in Georeferencer window
    • Use coordinate system: WGS 84 / Pseudo Mercator EPSG:3857
  • Set Transformationsparameter (yellow cog wheel)
    • Transformationstyp: try Helmert first
    • Ziel-KBS: WGS 84 / Pseudo Mercator
    • Ausbaberaster: a TIFF file you can find afterwards.
  • Select “Add Point” (small yellow star next to lines meeting)
  • Repeat until you have enough points (trial and error):
    • find fixpoint on old map, click on it
    • choose “From map canvas”
    • click on corresponding point on modern map
    • OK
  • Select “Start georeferencing” (green arrow)
  • Open resulting file as a layer in QGIS
    • Tip: change Eigenschaften: Transparenz
  • Experiement with different “Trasformation types”
    • under “Trasformation settings” (yellow wheel)
  • What are the main differences between a map from 1665 and  a modern map?
    • mapping techniques?
    • the landscape?
    • other things?

Try it out in the lab, you can also install QGIS and try it at your own computer: http://qgis.org/

Try also other maps, and compare. Can you find systematic differences in how hard it is?

Georeferencing can be the topic of Hausarbeit.