Does tracking a hike at night affect GPS accuracy?

The short answer

No. Darkness on its own has no effect on GPS accuracy. A phone works out where it is by listening to radio signals broadcast from satellites and comparing how long each one took to arrive. Radio at those frequencies travels through a dark sky exactly as it travels through a bright one, so a fix taken at midnight is built from the same physics as a fix taken at noon.

Anything that does make a night track look rougher is something other than the darkness: the trees you happened to be under, the valley walls beside you, where the phone was riding, or the ordinary shifting of which satellites are overhead at that particular moment. Every one of those exists in daylight too.

Why light has nothing to do with a satellite fix

Night and day describe which side of the planet is facing the sun. The satellites a receiver listens to are not on the ground, and they broadcast continuously regardless of what the surface below them is doing. Nothing in the chain — the signal leaving a satellite, crossing the atmosphere, reaching an antenna in a jacket pocket — involves visible light at any stage. A receiver has no way to tell whether it is dark outside, because it never had a way to sense that in the first place.

There is one real thing that changes with the hour, and it is worth separating from the myth. GPS satellites circle the earth roughly twice a day, so the arrangement of satellites above any particular spot at 3am is not the same arrangement as at 3pm. Sometimes that geometry is a little better, sometimes a little worse, and it shifts steadily through the day and the night alike. It is a genuine source of small variation in how tight a fix is — but it is a function of the clock and the orbits, not of sunlight, and it will hand you a slightly loose window in the middle of a sunny afternoon just as readily.

Where the worry usually comes from

The instinct is a good one applied to the wrong device. A motion-triggered wildlife camera strapped to a tree genuinely does struggle at night, and needs infrared illumination to produce a usable image, because it forms a picture out of light arriving at a sensor. Take the light away and there is nothing left to build a picture from.

A GPS receiver is not that kind of device. It is not forming an image of anything; it is a radio listening to timing signals from space. The word "signal" doing double duty across both worlds makes the two feel more alike than they are. Darkness is total for one and completely irrelevant to the other.

The other half of the instinct is that a night walk simply feels less certain. The map is harder to read at a glance, landmarks are gone, and the sense of not quite knowing where you are transfers onto the recording — which was quietly logging points the whole time, exactly as it does in daylight.

What actually is different after dark

The screen, and therefore the battery

This is the real difference, and it has nothing to do with accuracy. In daylight a phone can stay in a pocket for long stretches. In the dark, people check the map more often and turn the brightness up to read it, and the display is usually the single largest power draw on the phone — larger than the GPS receiver itself on a long walk. A night hike that ends with less battery than the same daytime route almost always spent that difference on the screen.

The cold

Nights are usually colder than the afternoons around them, and a cold battery reports less usable charge than the same battery warm — the chemistry slows down, then recovers when it warms up again. That can make a night walk look harder on the phone than it really was. It is a battery effect, not a positioning one; the recording itself is unaffected.

Where the phone ends up

Cold weather means jackets, and jackets mean the phone often ends up in an inside pocket, under a pack strap, or inside a glove. A body blocks satellite signals more than open air does, so a phone buried under layers can produce a slightly noisier line than the same phone riding in an outer pocket or a shoulder strap. That is worth knowing precisely because it is easy to mistake for a night-time effect when it is really a clothing one.

Things that trip people up

• Assuming a new moon, a full moon, or heavy cloud makes any difference — none of them do. A satellite signal is not moonlight, and cloud is nearly transparent to it.
• Reading a rough patch in a night track as a night problem. Check what you were walking under at that point: dense canopy and steep valley sides degrade a fix at any hour, and they are the usual explanation.
• Expecting a headlamp, a torch, or a lit screen to help the receiver. Nothing you illuminate on the ground reaches a satellite, and the fix comes entirely from what the antenna can hear of the sky.
• Blaming darkness for a battery figure that surprised you. Brightness, screen time and cold explain nearly all of it, and all three are worth checking before concluding that night recording is somehow more expensive.
• Comparing a night route against a daytime one on the same trail and reading small differences as significance. Two recordings of the same path always differ a little, in either direction, whatever the hour.

Where TrailCam fits in

TrailCam records a route in the background, so the screen can stay off for most of a night walk and the track keeps building anyway — which is also the cheapest way to run a phone in the dark. It follows your system light or dark appearance when you do look at it, keeps video clips, photos and voice notes pinned to the spot where you took them, and lets you replay the route on the map afterwards. Export to GPX 1.1 or CSV is part of the optional TrailCam Pro upgrade; the app is free to download.