By Dave Field
I found some useful free apps for navigating to your favorite cave searching spot using your smartphone, pad or tablet. The first is ViewRanger GPS. Assuming your device has GPS, this makes your phone or tablet essentially a handheld GPS. You may also be able to locate your position using cell towers, but I have not looked into this. Location Services on the device must be activated for this to work. It has a nationwide topographic base map at 10-foot intervals. Not too detailed, but adequate for most navigation. More detailed maps can be purchased from their website at a modest cost.
Waypoints that you wish to navigate to are called Points of Interest (POI). A menu on the map can be pulled up that has an option to enter coordinates. In the U.S. you need to make sure it is set to North (hemisphere) and West (of the prime meridian). I get coordinates of awesome looking karst features from LiDAR and Google Earth to enter. After entering the coordinates, the cursor will move to that location on the map. Then go back to the menu and Create a POI. This POI can later be called up and navigated to.
Likewise, when you are walking through the woods and come upon a nice pit no one has ever been in (it happens!), you can make a POI for that location so you can navigate back to it when you have your vertical gear.
The prevalent accuracy of a phone GPS is about 3 meters with open sky. As with even the best GPSs, accuracy drops significantly under a heavy canopy, perhaps around 10 meters. My tablet does not have a phone or data plan, and ViewRanger still works. Therefore, it should work on your phone even if out of cell tower range.
ViewRanger has many other functions found on handheld GPS such as tracking and setting up routes, which can be done on their website. So, your handheld GPS will soon be a garage sale item.
The next app is GPS Status. This is is a simple app that shows the locations of GPS satellites behind a compass, and has a bar graph at the bottom to show satellite strength. Will give your position, heading, automatically determines declination at your location, speed, etc. Has a good online users manual. The pitch/roll function could be used to do dips on strata, and for leveling the compass for strike measurements (as will the bubble level in the middle of the compass). This is better than other clinometer apps I have seen because you can lay the phone flat instead of on its edge. My phone indicates that this app is a bit of a battery hog, so beware.
The last is GPS Photo Viewer. This is a convenient app for getting the coordinates of where a picture was taken. So, when you take a picture of that pit no one has been in, you can get the location of it from the picture. Again, “Location” on the device will need to be turned on to get the location stamped on the photo. In my use of the app, it seems to work best if you open your camera from inside the app, where there is an icon to do so.