I have an exiting map with several layers. Some layers contain raster maps, others have other elements (such as vector data - SDE Feature Class). All layers are in Finland_Zone_3 coordinate system: Now I need to update some maps. The new maps are in different projection. They use EUREF_FIN_TM35 coordinate system. The new maps are TIFF files and they don't seem to have projection information embedded (when I try to import them with ArcMap I get error 'The following data sources you added are missing spatial reference information. This data can be drawn in ArcMap, but cannot be projected'). I have tried to add 'spatial reference information' / define correct coordinate system to the TIFF(s) before adding them to my map, but I have had no success. The map always gets shown few 1000s of kms west from where it should be. I have also tried defining correct(?) transformations but this has had no effect. 1. Change spatial reference of TIFF with arcgis catalog to 'geographic coordinate systems ->, Europe ->, EUREF FIN.prj' 1. change spatial reference of TIFF to 'Projected Coordinate Systems->,Continental->,Europe->,ETRS_1989_LCC' (which I understand is close enough to EUREF_FIN) with arcCatalog 5. but this time I cannot see the imported map at all. Selecting imported map layer and 'zoom to layer' does not do anything. Do you have 'EUREF FIN TM35FIN' in the projected coordinate systems->,National Grids folder? Try defining the TIFF to that using its property page in ArcCatalog. Make sure you have write permissions for the TIFF and its folder as that sometimes causes a problem. If you don't have the prj file, or changing the definition to it doesn't work, try using the ETRS89 UTM zone 35N definition in the UTM->,Other GCS folder. The parameters are all the same. You will need to set the geographic/datum transformation. You should use the KKJ_To_EUREF_FIN or KKJ_To_ETRS_1989_2 transformation, depending on what you use. Transformations are always defined in a particular direction (from A to B), but so far all the methods we support are inversible. The dialogs just don't bother to flip the transformation names if the data is in the opposite direction. Some of my maps are constructed as tens or hundreds individual TIFF files. Obviously I would rather not change the spatial reference to each of these individually. Will I achieve correct results if I define a new raster dataset in my SDE server, define it's spatial reference to the correct one, and then import all those TIFFs to this dataset? another question - if I define a transformation for my map raster, and the final raster is large (36000*64000) - is this a performance problem? Would I need to do the tranformation off-line and use the transformed raster to avoid performance hit of the on-line transformation? How can I do that? Source.