Does taking a phone call affect GPS tracking on iPhone?

The short answer

A phone call does not pause, slow down, or end a GPS track that is already recording. Route recording is a background task that iOS keeps running once an app has permission to use location in the background, and taking a call does not remove that permission or shut the app down. The call takes over the screen and the speaker for as long as it lasts; the GPS receiver goes on producing position fixes the entire time, whether the call is thirty seconds or twenty minutes.

Two separate pieces of hardware, doing two separate jobs

A call runs on the cellular radio, the same piece of hardware that handles texts and mobile data. A GPS track runs on a completely different receiver that listens for satellite signals rather than a phone network. Nothing about answering a call asks the GPS receiver to stop, because a call was never routed through it in the first place. The two can run at exactly the same time because neither one is waiting on the other to finish.

This is the same reason GPS tracking keeps working in places without a signal at all: it was never depending on the cellular radio to begin with. A call obviously needs that signal and a route recording obviously does not, which is part of why one can be present and the other absent without either affecting the other.

What the call interface actually takes over, and what it does not

Answering a call swaps the display to the system call screen and hands the speaker or earpiece to the call, and if the tracking app was open on screen, it gets pushed to the background the moment that happens. That is an ordinary backgrounding, the same thing that happens when the screen locks itself or another app is opened on top — the process behind the tracking app keeps running, it is just not the thing currently in front of you. A route recorder with permission to use location in the background does not need to be the app on screen to keep logging points.

What genuinely would end a track is force quitting the app, which is a separate and much more deliberate action — swiping it away in the app switcher, not answering a call. That distinction, and what force quitting actually does to a track already in progress, is covered in the guide on force quitting and GPS tracking.

The one place a call can cost something

A call is not free — the cellular radio and the speaker both draw power for as long as it runs, on top of whatever the GPS receiver was already using. On a long hike with a handful of calls sprinkled through it, that adds up the same way any other use of the phone during a hike does. It is a real but separate cost sitting alongside the track, not a cost that changes anything about how the track itself is recorded.

Things that trip people up

• Assuming a call counts as leaving the app the way force quitting does — it backgrounds the app the same way locking the screen does, which does not stop a track that has permission to run in the background.
• Ending a call quickly out of worry that the hike is not being recorded while the phone is showing the call screen — the GPS receiver was never routed through the call in the first place, so nothing is being missed.
• Blaming a gap in a track on a call that happened around the same time — a genuine gap almost always traces back to something else, like the app actually being force quit, not to a call that only ever used the cellular radio and the speaker.
• Turning on airplane mode before a call to try to protect the track — airplane mode would remove the ability to take the call at all, and does nothing extra for a GPS receiver that was already unaffected by the call.

Where TrailCam fits in

GPS route recording on TrailCam keeps running through a locked screen, another app in the foreground, or an incoming call, because none of those remove the background location permission that keeps it going. If the app is ever interrupted mid-walk, it offers the unfinished route back to you the next time you open it. TrailCam is free to download.