i put together a couple of things on youtube showing various scenarios for using mapwarper. for folks new to OHM who want to know how to bring in source material that isn’t already geo referenced, this should help a bit.
1) In this one, i take a 1834 survey map of the Albany terminus of the Erie Canal, load it into mapwarper, rectify it, and then bring it into JOSM for editing:
2) In this one, i take an aerial image from 1952 which in theory contains the footprint of Clearview Speedway in South Westerlo NY (from USGS earthexplorer), bring it into mapwarper and align it. the scenario is a little different from the survey map, the image is much larger and a few issues show up that need to be addressed:
3) In this one, I look at what can be done to deal with the case where there is more than one map on a single scanned image, in this case something already scanned in on the NYPL website, but not quite usable as is: