To the best of my knowledge, no. You have to have the gps plugged in.
The 1.4 GB on your hard drive is what's used to get the maps on the gps. You could think of it as a zip file, which can't be used as a normal file.
I"m a bit new to this too though. I'd prefer to not have to plug in the gps, but it doesn't seem to be a big issue.
Learning how to use BaseCamp... now that's an issue. It's very unintuitive, and for something you don't use that often, that's not a good thing.