Commons:Georectification

Georectification or map warping is the process of linking a pixel file with coordinates on a map. On https://warper.wmflabs.org/ we have a prototype that works on Commons files, but stores the rectification data on wmflabs. We want to store this data on Commons too so we have everything in one place.

General contents of data file

To be able to correctly rectify a Commons file on OpenStreetMap, we need the following data:

• Map image - The image that we're rectifying. We store the filename, entity id and the sha1 hash of the file.
• Geo control points (GCPs): A list of points that are combination of x & y for the pixel and lat/lon for the point on the map
• Pixel mask: A list of pixels (x and y or relative???) to crop the image
• Map mask: A list of coordinates (lon/lat) the correspond to the pixel mask crop on the map

Exact format is being discussed at User talk:Multichill/Map warping format and will be published here.