Does turning off Precise Location affect GPS accuracy on a hike?

The short answer

Yes, and more than most settings on a list like this one. With Precise Location off, a tracking app is not handed a slightly less accurate GPS fix — it is handed a different kind of information altogether: an approximate area rather than a point. A route built from a string of approximate areas does not come out as a slightly rougher version of your walk. It comes out blocky, jumping between positions that make no sense for how fast a person walks, with the shape of the trail lost almost entirely.

Two settings that get mistaken for one

Location Services access

This is the permission most people already think of — While Using the App, or Always — found under Settings → Privacy & Security → Location Services → the app in question. It decides whether an app gets location updates at all, and whether that continues once the app is in the background. This is the setting that matters for whether a recording keeps going with the screen locked or another app open.

Precise Location

This is a different toggle, sitting just below access on the same settings screen for a given app. It does not decide whether an app gets location — it decides the resolution of what it gets. On, an app receives your actual coordinate, as good as the current GPS fix allows. Off, it receives a coordinate blurred to somewhere inside a wide area, with no way to tell where in that area you actually are.

What "approximate" location actually gives an app

Apple built this as a genuine privacy feature, not a lesser version of the real thing. An approximate location is not a rounded-off version of your exact position — it is a different value entirely, describing an area rather than a point, and it changes far less often than a precise fix does. For an app checking the weather or suggesting somewhere nearby, that is plenty, and it is also less than the app strictly needs to know.

For a route recording a hike, it is not enough at any resolution. Distance, pace and elevation gain are all computed from the sequence of points a track is made of; feed that calculation an area a few kilometres wide instead of an exact coordinate and every one of those numbers stops meaning anything. The line on the map would not wander a little, the way ordinary GPS noise does under tree cover — it would snap between distant points that have nothing to do with the pace of a person on foot.

Why iOS defaults toward approximate at all

Most apps that ask for location do not need to know exactly where you are standing — a weather app, a search app, most anything showing nearby results works fine with an approximate area, and giving out less than an app strictly needs is the more private default. iOS reflects that by offering Precise Location as a choice you can grant or withhold separately from access itself, rather than folding the two together.

A handful of apps are the genuine exception — navigation, and anything recording where you actually went — and those are the ones worth checking deliberately, rather than assuming the default that suits most other apps also suits this one.

Checking it

Settings → Privacy & Security → Location Services → the app in question shows both settings on one screen: the access level above, and a Precise Location toggle below it. It is on by default for most apps the first time you grant location access, but it can be switched off by hand later, or during a general privacy tidy-up that touches several apps at once without singling any of them out.

If a recorded route has ever looked blocky or jumped in a way ordinary GPS noise does not explain, this toggle is worth checking before anything else — it produces a symptom that looks nothing like the usual causes of a rough track.

What TrailCam needs

TrailCam records a route from the exact coordinates an iPhone's GPS produces, so Precise Location needs to be on for the recording to mean anything — the app has no use for an approximate area the way a weather app would. Both settings are offered the first time you grant location access, and either can be checked afterward under Settings → Privacy & Security → Location Services. TrailCam is free to download.