GPS thoughts

My trail use of GPS is much like big_load's, mostly for spot checks on the trail. I've never used the tracking feature.

However, I do use GPS almost every day for my bike rides. The app I use to keep track of mileage utilizes iPhone GPS feature.

Mrs. big_load has a terrible sense of direction under most circumstances.  But the night sky changes everything for her.  If she can see a patch of stars, she can find her way.  Just don't ask her to guess which way the wind will blow when the air cools off at night.

I find a GPS very useful for off trail hiking. One particular destination is crisscrossed with game trails, and it's easy to get side-tracked and miss a narrow ridge that is basically the only way to get there. A few hundred feet in either direction means a fair amount of backtracking.

Id'll also mention that I have a basic unit, so other than the track back function, there are no built in maps. I still rely on paper maps, and I always carry a compass as a backup.

While driving, I've had a GPS direct me to take a "road" (and I use that term in the loosest definition) I wouldn't even think of taking a jeep on.

I also find Google maps very useful. They seem to be very good at re-routing around accidents. In the end, a GPS is a tool, with the utility and limitations of any other tool.

I have a sextant as well, and I think it's wise the Navy continues to teach its use.  It would be rather easy for someone like China or Russia do disable or jam the satellites used. 

Agree with what Travis well summarized.

I recently did a hike in Death Valley National Park badlands in the Black Mountains where a GPS track was valuable. During most of my day hiking, backpacking, or skiing a GPS track is merely an amusement.

I had never actually bought and used a cellphone daily until buying the moto G smartphone in the fall on 2015. My decades honed topographic map skills are at an expert level so serve me well. But it was obvious there were advantages to using a GPS device in some circumstances and it was on this hike I expected to see those advantages with more clarity. I downloaded the pricy Trimble Navigator app and have used it several times making tracks on day hikes. I bought the Trimble full $100 California topographic map set 32gb SDcard that conveniently has several spare gigabytes for other cellphone stuff. The map set very importantly includes a map view that shows land ownership. As a landscape photographer of obscure places, that is of huge value when driving in rural areas and wondering if what is across barbed wire fences is either private as in NO TRESPASSING lands or public lands since many of the latter are not signed so.

During my noted hike the first instance of the advantage of this app was upon entering a wash canyon mouth, as I was certain it was the correct one because it exactly matched the one I'd been looking at so much on the topo. By map alone that would not have been certain until moving up the narrowing canyon then verifying the many wash turns matched the map. The bizarre badlands topography of the northern Black Mountains have considerable steep slopes with less than 40 foot granularity of USGS 7.5 minute topographic maps. Accordingly features are difficult to assess.

During the 11 mile off trail hike that ended a half hour after dusk in the dark, I had to negotiate climbing up through 3 puzzling badlands mazes of climbing 300, 100, and 150 feet uphill respectively to reach my destination interspersed by easier wash areas. Once down inside such narrow washes, one often cannot see left right forward or back because they snake around in weird ways. Thus orientation is difficult down inside such that returning on the same route as one came is not obvious. Like Zeke's comment of kayaking through mangrove islands.

And as someone that has done considerable night day hiking and backpacking, it was obvious GPS could make a huge difference when doing so off trail in the dark because recognizing landscapes can be very difficult as one can see only limited distances even with powerful headlamps. The slope of a mountain may just be 200 yards away and without moonlight one might just see blackness until moving closer. That is one reason I bought a cheap 5mw laser pointer because in inky dark mountain areas it can illuminate further than any headlamp, even my 2550 lumen eagletac mx25l3c nichia 219 flashlight.

David

The US Military has the option to shut off GPS.

Many of the GPS enabled weapons systems will navigate for a time after the loss of a GPS signal.

GPS does not work in space.

Which brings navigation back to inertials for space navigation. The last I 'heard' was a hydrogen atom makes a good gyro and there are some great chip accelerometers in existance. There was a move from SINS (ships intertial navigation) to GPS and now the move is to PINS (precision intertial navigation). The idea with PINS is with one navigation system to be able to navigate on land, in the air, on the water, under the water, or in space.

Thus the return to train navigators in dead reckoning. A good understanding of dead reckoning is helpful when using inertials.

They'd turn on full encryption. I expect the other systems would do the same.

They'd also fire up local area jammers. That happened in San Diego when a tech was testing a system and hadn't disconnected the antenna: shut down every ATM in the city lol. Turns out the ATM system uses the highly accurate God time signal to time stamp transactions. Oops.

GPS is nice, but when I came up, there was no such thing.  All of the serious navigation was done with a map and compass for the most part.  Of course, we all know there are other ways to figure out where you are at and where you are going.

The thing I like about keeping those skills up is they don't require a battery!!!  ;-)