Land Navigation · 6 min
GPS, phones and what they cannot do
Why this matters
Your clients will navigate by phone whether you approve or not, and you will use a GPS yourself because it is genuinely good. Knowing precisely where it fails is what keeps it a tool rather than a single point of failure.
By the end of this lesson you will be able to
- State what a GPS is reliably good at and what it is not
- Read coordinates in the systems a Ranger will ask for
- Plan for battery, cold and canopy
What it does well
- Tells you where you are, to within a few metres, in conditions where no other method works: fog, dark, featureless forest
- Records a track you can follow back out. In flat, thick country like the western Adirondacks this is worth a great deal
- Gives a coordinate you can read to a dispatcher, which shortens a rescue dramatically
What it does badly
- Batteries die, and lithium and lithium-ion both lose capacity fast in the cold. A phone at 10°F can go from 60% to dead in minutes
- Screens fail: wet, gloves, glare, a drop on rock
- Accuracy degrades under heavy canopy, in deep valleys and against cliffs, exactly the terrain where you most want it
- It shows position, not route. A dot on a screen does not tell you the cliff band between you and the trail. A map does
- Downloaded maps are only downloaded if someone actually downloaded them, and phone coverage in the Adirondack interior is largely absent
The professional standard
Carry map and compass, know how to use them, and treat electronics as a supplement. A guide whose navigation stops when a battery dies is not navigating. Carry the GPS anyway: used together they are better than either alone.
Coordinates
| System | Looks like | Notes |
|---|---|---|
| Decimal degrees | 43.9712, -74.4321 | What most phone apps show. Fine for a dispatcher |
| Degrees, minutes, seconds | 43° 58' 16" N, 74° 25' 56" W | Traditional. Watch the units when reading aloud |
| UTM | 18T 552340E 4869210N | Metres on a grid. Easiest to plot on a paper map with a grid tool |
Whatever you use, say which system you are reading when you pass a position, and read the digits slowly, twice. Most of the time lost in a rescue is spent resolving a bad coordinate.
Cold and power
- Keep the phone or GPS inside a layer, against the body, not in an outer pocket
- Carry a charged power bank, also kept warm, and the right cable
- Put the phone in airplane mode. Searching for a signal it will never find is the fastest way to flatten it
- Carry spare lithium AA cells for a dedicated GPS. They handle cold far better than alkaline
From the field
Your client's phone has the whole route on it, and it dies at the col at 15°F. This is a non-event, because you are carrying the paper map, you have been thumbing it all morning, and your own GPS is on lithium cells inside your jacket. That is what redundancy looks like in practice.
This lesson is part of the NYS Licensed Guide Exam course. Open it in the course to answer the retrieval checks that go with it, track what you have read, and quiz the whole unit. Lessons, quizzes and the glossary are free.