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UID:pretalx-foss4g-europe-2025-CYVEPS@talks.staging.osgeo.org
DTSTART;TZID=CET:20250716T110000
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DESCRIPTION:More than 30000 scanned historical maps from the archive of the
  National Land Survey of Finland were georeferenced and made available as 
 open data through download services. The oldest maps which were georeferen
 ced in this project are from 1860s.  Maps until 1917 cover the area of the
  Grand Dutchy of Finland in the Russian Empire\, and since 1917 the area o
 f the independent Republic of Finland.\n\nAll the georeferenced maps were 
 originally produced into some regular mapsheet grid. In theory this makes 
 georeferencing easy because the four corner points of a mapsheet can be us
 ed as ground control points\, and the georeferenced coordinates are known 
 by the grid. However\, during the period 1860-2020 about 15 different maps
 heet grids and 5 different coordinate systems have been used and most of t
 hem were not available as spatial data in a digital format. Also\, the map
  makers have not always honored strictly the mapsheet grid which make issu
 es for automatic processing.\n\nThe georeferenced maps were published in C
 loud Optimised GeoTIFF format in two versions. One version preserves the w
 hole information of the scanned map and contains the original marginalia a
 nd possible handwritten remarks\, while the other version is clipped to th
 e area of the actual map for making it easy to build seamless mosaics from
  adjacent map sheets. Maps were published through the Geoportti Research I
 nfrastructure that is particularly targeted for researchers\, teachers\, a
 nd students\, but that is open for everybody. Maps can be downloaded with 
 a web application or as mass download by using HTTP\, FTP\, or rsync. Maps
  can also be searched and downloaded with STAC.\n\nIn this talk the genera
 l workflow of georeferencing historical maps is presented with examples ab
 out typical oddities in historical maps which can make the workflow fail. 
 Reasons are also given for the decisions that were made about the file for
 mat\, compression\, and image metadata.
DTSTAMP:20260527T015047Z
LOCATION:SA01
SUMMARY:Georeferencing and publishing Finnish historical maps - Jukka Rahko
 nen\, Külli Ek
URL:https://talks.staging.osgeo.org/foss4g-europe-2025/talk/CYVEPS/
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