If you buy DeLorme's xMap software then you can (evidently) make your own maps from public data sources. If you look at the info on their website it's really confusing - there are many different versions of xMap ranging from about $250 to over $1,000. PN-40 owners say that if you call DeLorme they will sell you the basic version of xMap for $100. But prices have evidently increased since then.