How your iPhone figures out where it is

Your iPhone does not get its location from one source. It combines several, then merges them into a single best guess. The Global Positioning System is the foundation: the phone listens to timing signals from a constellation of satellites overhead and calculates how far it is from each one. With four or more satellites in view, it can pin down a latitude, longitude, and rough altitude. Modern iPhones also read other satellite systems such as GLONASS, Galileo, and BeiDou, which means more signals to lock onto and a faster, steadier fix.

On top of the satellites, iOS cross-references nearby Wi-Fi networks and cell towers against a database of known positions, and it leans on the built-in accelerometer, gyroscope, and compass to track movement between readings. Blending all of this is what lets your phone find itself quickly in a city, where a bare satellite signal alone would struggle. Apps never talk to the satellites directly; they ask iOS for the position, and iOS hands back the merged estimate.

So how accurate is it, really?

Under good conditions, an iPhone is accurate to within a few meters. Outdoors with an open sky, you can expect roughly three to five meters of error, which is why turn-by-turn navigation knows which side of the street you are on. That number is a typical case, not a guarantee. Accuracy is a moving target that depends on how many satellites the phone can see, how strong their signals are, and how much help the Wi-Fi and cellular data can offer.

It helps to think of GPS accuracy as a circle around your true position rather than a single dot. When that circle is small, your phone places you almost exactly right. When conditions degrade, the circle widens, and the reported point can drift several meters or more from where you actually stand. The blue dot on a map even shows this: the soft halo around it grows when the phone is less sure of itself.

What makes accuracy better or worse

Several factors push iPhone GPS toward the precise end or the fuzzy end of the range:

Sky visibility: a clear, open view of the sky gives the best fix. Anything blocking the satellites hurts.
Buildings: tall structures in dense cities cause "urban canyon" errors, where signals bounce off walls before reaching the phone and throw off the math.
Indoors: roofs and walls weaken or block satellite signals, so the phone leans heavily on Wi-Fi and cell data, which are less precise.
Tree cover and terrain: heavy foliage, canyons, and mountains can absorb or reflect signals.
Weather: thick cloud and storms have a modest effect; dense atmosphere can slightly delay signals.
Time to lock: a fresh, cold start takes longer and is less accurate in the first seconds than a warm fix that already has satellites tracked.

When iPhone GPS is most likely to be off

The estimate is least reliable exactly where people often need it most: indoors, in parking garages, on subway platforms, and in downtown cores ringed by skyscrapers. In those spots the phone may report a position tens of meters away, snap your dot to a nearby road, or jump as it reweighs Wi-Fi and cellular signals. You may also see drift right after you walk out of a building, while the phone reacquires satellites and the accuracy circle shrinks back down.

None of this means the hardware is broken. It is the normal behavior of a system that is always estimating from imperfect signals. For everyday navigation and tagging a photo, a few meters of slack rarely matters. For anything that depends on an exact coordinate, the estimate is simply not built to be precise to the foot.

Setting an exact location yourself

If you want a precise spot instead of a best guess, you can stop relying on the estimate entirely. A Fake GPS app lets you choose the coordinates your iPhone reports, down to the exact latitude and longitude you type in. Rather than hoping the satellites place you correctly, you set the point yourself and every location-aware app reads that exact position.

The workflow is simple: search for a place by name, drag the map and drop a pin where you want it, or paste in coordinates directly. From there the app feeds that position to iOS, so the spot is fixed and repeatable rather than drifting with signal conditions. This is the core idea behind a GPS location changer — you control the exact value instead of accepting an approximation.

Exact coordinates: set latitude and longitude precisely, with no accuracy circle to worry about.
Repeatable: the position stays put instead of wandering as you move between buildings.
Device-wide: apps reading your location see the spot you chose, not an estimate.

The short version

iPhone GPS is accurate to within a few meters outdoors and noticeably less so indoors or among tall buildings, because it blends satellites with Wi-Fi, cellular, and motion sensors into a single estimate. That estimate is good enough for most daily use but is never a perfect coordinate. When you need an exact location rather than a best guess, setting a fake GPS location puts the precise point entirely in your hands.