Yes, the photos need to be in the Map module to tag them in the Map module.
To put 300,000 images in the filmstrip , you need to put all the images in one collection.
A lot of my photos are geotagged, but only a few (relatively speaking) have been keyworded with location names. In LR is it possible to use the Map Module to view the locations of all photos in the library? That would make it quite easy to find all photos taken within a certain area.
I can show on a map all 28000 geotagged images in my catalog. I don't usually even show the filmstrip under the map, I just click on All Photographs in my Library Module, and then go to the Map module. If you're going to do this for purposes of adding keywords, you don't need ALL of your photos on the map anyway, you can do this in bunches.
Thanks all! It took all morning to import just some of images into LR (I use Bridge normally), and those that imported okay (most of them) show up nicely on the map like you all said they would. A shame I can't view them like this in Google Earth, but the LR map view is still very helpful.