navit-project.org

I'm new to using Navit and have a few questions. My background for using this is I have fixed up an older Jeep for traveling offroad, and am looking into using Navit for basic navigation. I will be using just one map file (of my home state in the US), I don't need to search for anything, and I don't need routing. I just want to see where I am on a map. I've been going through the code, and started to get the binfile code working. My first question at this point is what is the purpose of the index file within the binfile? Assuming that it contains a bunch of entries, is there a struct somewhere describing these entries?