U.S. Army Survival Guide ($2.99 for iPhone/iPad, free Android version available from a different developer)
This app is useful for just about any trip to the outdoors. As the name suggests, this app contains the official field manual of the U.S. Army. But that doesn't mean you need to be a member of the army to use it; in fact, the app is useful for just about any trip to the outdoors. Outdoor fanatics in particular will enjoy the survival guide, which covers different kinds of environments (desert, tropical, cold weather, sea, and more). In addition, you'll find information on first aid, shelters, water procurement and more. Whether you need to learn how to tie a knot or build a fire, this app can help you out. Clicking through the chapters is easy and there are pictures to go along with the explanations, too. Videos are all that the app is missing.
Park Maps ($0.99 for iPhone)
Park Maps (pictured) allows you to download high-resolution maps for more than 250 national parks, monuments and recreational areas in the U.S. Once downloaded, the maps are available offline, so that you can consult all the points of interests while you are out and about. Whether you want more information about wildlife sighting areas or you need to find a restroom inside one of the parks, this app will help you do so.
Knot Time ($3.99 for iPhone)
Out in the wilderness tying knots correctly is vital and the Knot Time app is here to help. From boating to fishing to mountaineering, the 33 knots are organized by what they are used for. When you download the app, you automatically download a how-to video for each knot, so it will be available offline when you are out and about. There is also a free version, Knot Time Lite, which covers just 9 knots.
Backcountry Navigator Pro GPS ($9.99 for Android, Windows Mobile version also available)
Backcountry Navigator works just like a complex GPS system would. In addition to topographical maps, this app comes with color aerials as well as road maps, all of which are available offline after the initial download. You can enter your own waypoints using longitude and latitude information or other grid references. When you're done with your trip, you can share it via email or social media so your friends and family can see what exciting places you have been to. If you don't want to shell out ten dollars right away, try the free demo version first.
MotionX GPS ($0.99 for iPhone)
MotionX GPS provides topographical maps that go beyond the national parks. Again, you can download maps before you go so you don't have to rely on 3G or 4G when you are hiking or otherwise engaged in the outdoors. In addition, the app also lets you save tracks and waypoints, and if you're in need of a compass, that is included, too. Whether you are cycling, hiking, running, sailing, or even flying, this app can be used on land, water and in the air. There is also an HD version for iPad ($1.99).