The Garmin Astro comes with a "base" map. If you want more detailed mapping information you can add any of the regional Topo Maps, the entire USA Topo or the entire USA Car package which gives you turn by turn navigation. The regional topo maps and the car package are easy to use. You just plug the micro SD card into the slot under the batteries in the astro handheld. If you want the entire USA on Topo or you pick the car package in the DVD format, you will need a Micro SD card to download the information from your computer. It really is not that hard but it does take a little more work. I have run my Astro with both kinds of Maps and it does a really nice job. Be sure to check out Garmin's newest 24K Topo Maps
for the highest level of terrain detail.
The Topo Maps are best from a hunting standpoint. The biggest advantage is knowing where your dog is in relation to either roads or waterways. It really helps when you can tell that your dog is on the other side of a creek or river.
The Car Navigation package worked pretty well, but compared to any of the Garmin Nuvi units, it is not as user friendly. I would recommend that you look at some of the newer car units before you invest in the car option for the Garmin Astro. Neither of the mapping options is required to run the Astro but it does give you more information if you want it.