A bit of a hijack of my own thread:
What this is all about is advising people on how to determine their location for if/when they have to call for help if they get stuck or their vehicle breaks down. And I'm thinking about in places like on the highway (or off!) in the southwest or plains states, where traffic may be light, exits are far apart, and the only landmarks are expanses of flat terrain. Most people probably don't pay attention to highway mile markers, but if you have a GPS device, in theory you should be able to find out the coordinates of your current location.
I have figured out how to do it in the Google Maps app (it's not "difficult," but it's also not intuitive). I know hiking GPS units display coordinates, but I don't know if the automotive navigation units do. I have an old Tom Tom GPS in my Jeep, and I don't think it allows me to access latitude and longitude. But I'll check on that.
Then I started looking at cell phone apps that might make this easier. I found a free compass app that's very easy to use, but requires the device to have a built-in magnetic compass. My old Samsung Galaxy SIII does -- my current Samsung J3 Eclipse does not. The compass app opens up with a display that includes the latitude and longitude.
Then comes the fun part -- a friend turned me onto an app that's a actually a fairly complete avionics package. We both looked at it because of daydreams about buying or building an ultralight aircraft. Ultralights can only only VFR (Visual Flight Rules) so they don't need (and the weight limitations won't allow) a complete set of expensive gauges and sensors. But this app, installed on a modest tablet, offers maybe 90 percent of the functionality of a modern "glass" cockpit (without any engine gauges or autopilot, of course).
There's a free version (B&W) and a Pro version (color, with the capability to interface with an external sensor module for real-time airspeed and altitude, rather than GPS). I've been playing with the free version. It's overkill for the purpose of finding your location to call for a tow truck, but it's fun to play with.
Looking at their web site, I just discovered that the Pro version is available for free to anyone who has access to US Department of Defence (DoD) and Intelligence Community users. So if anyone out there is military and you want to turn your Yugo into a ground effects aircraft, here's what you need:
http://a-efis.com/downloads (Scroll down for the GEOINT version)
If any of you are pilots and you'd be willing to download even the free version and try it out in an actual aircraft, I would be very interested to get some field reports on how it performs. It seems like it would make for a great backup system against the possibility of an instrument failure.