QGIS

Install QGIS (OS X)

Follow the discriptions on the Download QGIS page. For Mac OS X, you need to download and install:

• GDAL Complete 1.11 framework package or later (including NumPy)
• Matplotlib Python module
• QGIS 2.12 or later
• Install the following QGIS plugins (Plugins > Manage and Install Plugins...)
  • QuickMapServices (to use OSM as a base map for creating data)
  • Georeferencer GDAL (to create new georeferenced base maps)

If you want to easily execute the GDAL command line tools, add the Programs folder to your shell path. For example add this to your ~/.bash_profile:

export PATH=/Library/Frameworks/GDAL.framework/Programs:$PATH

Georeference Historical Berlin Maps

When importing historical maps as raster maps (images), you have to assign coordinates to the map to place the map at the correct location in a process called georeferencing.

• Make sure you have the Georeferencer GDAL plugin installed. If not, go to Plugins > Manage and Install Plugins..., then search for Georeferencer GDAL and install the plugin.
• Open the Plugin Raster > Georeferencer > Georeferencer...
• Download the map you want to georeference, for example by clicking on the download link for Berlin 1690 (image is provided in TIF format)
• Open the downloaded image in the Georeferencer plugin with File > Open raster
• In the dialog that will open, you have to select the coordinate system of the map (CRS). For the Berlin 1690 map, this information is given on the download page of the map (DHDN / Soldner Berlin, EPSG:3068).
• Next, you'll have to assign coordinates to points on the map so that QGIS knows where the map is located. The more precise you work here, the better the results will be.
  • Reference points for the Berlin 1690 map are again given on the download page (bottom left: 23100/19600, top right: 26300/22600). This coordinates are in the coordinates system of the map (Soldner Berlin).
  • Zoom in to the left corner of the map, select the Edit > Add point tool and click the corner of the map image. Enter 23100 for X / East and 19600 for Y / North in the Enter map coordinates dialog.
  • Use the image size (3662 × 3497) as source X/Y
  • Doing the same for all corners will give you 4 reference points
  • Adding more reference points will give more accurate results (see below for common reference points, this list is the final result)
• Open the Settings > Transform settings dialog to change the output configuration. For the Berlin 1690 map, you want to minimize distortion and modification because the map is already in a the right output format.
  • Transform typ: Thin Plate Spline (transforms the image so that all reference points map exactly)
  • Output raster: a file name of your chosing
  • Resampling method: Lanczos
  • Target SRS: Soldner Berlin/EPSG:3068
  • Load in QGIS when done: enable to automatically create a layer after georeferencing
• Click File > Start georeferencing

Georeferencing will take a while. Afterwards, you'll have a new layer with the georeferenced raster map. (If not, add layer manually with Layer > Add Layer > Add Raster Layer....)

Common reference points:

• Nikolaikirche (NW corner): 25180.244,21109.930
• Marienkirche (SW corner): 25149.560,21505.960
• Friedrichswerdersche Kirche (round front side): 24517.297,21030.755

Add Base Layer for Reference

To check that the map was georeferenced correctly, you can use a base map from a known good source such as Open Street Map as a reference.

• QuickMapServices plugin (OSM Mapnik)
• Open Layers plugin: Unfortunately, the Open Layers plugin was broken at the time of writing this article (zoom didn't work with QGIS 2.6.1 on OS X).
• Google Maps: To manually add Google Maps, follow this advice and add this Google Maps XML file as raster layer with Layer > Add Layer > Add Raster layer (more XML files).
• Berlin Orthophotos: Berlin's geoportal offers satellite images with high resolution with a very permissible license.
  • WMS: Add http://fbinter.stadt-berlin.de/fb/wms/senstadt/k_luftbild2014 in Layer > Add Layer > Add WMS/WMTS Layer
  • Offline: Download satellite images and add them as raster layer. Unfortunately, the images come in a format called ECW, which is a pain to set up on OS X:
    • Make sure you have QGIS 2.6.1 with GDAL Complete 1.11 from here
    • Download and install ECW plugin v1.11.0-1
    • After the ECW installation, follow the instructions in VERY IMPORTANT POST INSTALL.textClipping that's part of the ECW install package to install the binary drivers for ECW support. In short, this involves downloading the ERDAS ECW/JP2 SDK v5.1 (MacOSX) and copying files into the GDAL installation directories.
    • Download some ECW files from the Orthophotos 2014 set, for example 392_5820, which includes Alexanderplatz.
    • Open QGIS, Layer > Add Layer > Add Raster Layer... and open the .ecw that's part of the downloaded zip file.
    • Use ETRS89/UTM zone 33N (EPSG:25833) as the coordinate system

Currently the most reliable option is the QuickMapServices plugin. Note that by using another map for referencing, you create a derived work and must comply to the map's licensing requirements.

Vectorize Map Information

When vectorizing information, please make sure to use maps where we have usage rights as a reference (and not other maps such as Google's) to avoid copyright issues.