I´m trying to recover a previous version of a Qgis file, because I started playing around with CRS, and saved the file and closed it, thinking next time it woud be easy to get everything back into place.. BUT now all my layers are flying around all over the place and I can´t get them back to matching one on top of the other even when they apparently ahve the same CRS and projection (I´ve been trying to for hours, apparently there´s something seriously wrong with native projections.. but I did have them neatly lined up, so I don´t know what happened) So, I think the easiest would be to go back to last night´s version of the file. Except, when I right click the file and hit restore previous version, there are no previous versions to choose from... any ideas? I´m running Qgis Essen on Windows Parallels (I´m on Mac Yosemite OS).
QGIS stores the data in several places:
- the data of every vector and raster layer is stored in the file(s) according to the format you have chosen (shapefile, spatialite, Geotiff etc)
- Web services might be cached locally, otherwise only the connection parameters are stored
- all layer and styling information is stored in a .qgs project file, and backed up in a .qgis~ file until the next save operation
So it depends on the steps you did where the changes were stored. CRS information is stored in vector/raster files as well as the project file.
For shapefiles, QGIS stores the projection information also in a .qpj file which is not used by any other software. You have to delete that if you reload the data from external sources. Otherwise, you have to use
Set Layer CRS to assign back the right projection.