<html><head></head><body dir="auto" style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="ApplePlainTextBody"><div class="ApplePlainTextBody">"Orthorectification" is the cartographic process here. This means "stretching" an image to remove distortion so it will match (or closely match given mathematical constraints) the spatial accuracy of a given map (like OSM's data) so that a close-enough match between the image and the existing map data occurs, furthering additional editing which is reasonably accurate. OSM's Java-based editor JOSM has a plugin (this software is a bit "early" although it has been around for years) called PicLayer [1]. This allows orthorectification of numerous image types via scaling, rotating and the like so that the image can be overlaid upon OSM data in a layer that furthers additional editing.<br><br>Orthorectification can "breathe new life" into old, archived map data at a different scale (or with skew or terrain-blocked or horizon-view distortion) by "bringing them into topological harmony" with the present dataset.<br><br>SteveA<br><br>[1] https://josm.openstreetmap.de/wiki/Help/Plugin/PicLayer</div></body></html>