GPS and internet access are related in many phone apps, but they are not the same system. A phone can often calculate a satellite-based position without mobile data or Wi-Fi. What it cannot do offline is instantly send that position to a remote website.
A phone's GNSS receiver listens for timing signals from navigation satellites. From those signals it can calculate a position. The satellite signals arrive by radio directly; they are not downloaded through your mobile-data allowance.
That is why offline navigation and GPS logging are possible in principle.
Phones can use network assistance to obtain satellite data, time information and coarse starting estimates more quickly. Android can also combine satellite, Wi-Fi and cellular observations through location services.
Without network assistance, the first accurate satellite fix after a long gap or major movement can take longer, especially with poor sky visibility.
The phone may still know where it is locally while the remote viewer sees no new points.
A well-designed tracker can store timestamped location records locally when the network disappears and send them later. This is useful in rural areas, tunnels, foreign travel without roaming and temporary mobile-network outages.
The map should make the distinction between the recording time and upload time clear. A batch arriving at once after reconnection does not mean the phone travelled the whole route in that instant.
LocationOf can be used in situations where connectivity is intermittent, provided the Android app remains able to record positions. Real-time web viewing obviously depends on data reaching the server.
If you also want to know whether a SIM is necessary, continue with Does GPS work without a SIM card?.
You can demonstrate the separation between GPS and internet access yourself. First let the phone obtain a stable outdoor location while connected. Then use a navigation or logging app that supports offline operation, disable mobile data and Wi-Fi, and observe whether the device continues to produce coordinates. Do this somewhere safe and do not disable connectivity if you need the phone for an emergency.
The important part is to distinguish the coordinate calculation from the map display. If the app has not cached map tiles, you may see a blank map even though the phone still has a valid latitude and longitude. Likewise, a web dashboard will stop receiving new points because there is no route to the server.
When you reconnect, check whether the tracker backfills the missing route with the original timestamps. That is the behavior you want from an offline-capable journey logger.
People often test “GPS without internet” by opening a map after disabling data. That combines three different functions. First, the phone must calculate or obtain a location. Second, the app needs map imagery or vector data to draw the surroundings. Third, a live-sharing service must transmit the position to another device or server.
The first can work without internet because GNSS satellite signals are received directly by the phone. The second can work if the map was downloaded or cached in advance. The third cannot be genuinely live without some communications path. An app may store points and send them later, but the remote viewer will not see them until connectivity returns.
This explains why a blank map does not necessarily mean GPS failed, and why a web tracker going quiet does not necessarily mean the phone stopped knowing its own position.
Airplane mode is designed to disable transmitting radios such as cellular service and, depending on the device and settings, Wi-Fi or Bluetooth. GPS/GNSS reception is passive, so many Android phones can still obtain satellite location while airplane mode is enabled. The exact behavior can vary by device and operating-system configuration.
If Wi-Fi and mobile data are both off, an internet-based tracker cannot upload new points even if the handset continues to calculate coordinates. This makes airplane mode a useful demonstration of the difference between local positioning and remote tracking, but do not use it as your only test because assisted data and cached information may affect acquisition speed.
If your real concern is using a phone with no cellular subscription at all, read GPS without a SIM card.
For travel, hiking and rural driving, a useful tracker should treat temporary network loss as normal rather than as an error that destroys the route. It should timestamp each point when it is captured, save it locally, preserve chronological order, and synchronize later when a connection returns.
When you test LocationOf or another logger, deliberately create a short connectivity gap in a safe setting. Record a route, reconnect, and inspect whether the missing section appears with the correct historical times. This is much more informative than merely checking whether the latest map marker moves while Wi-Fi is available.
See recording a road trip and GPS tracking for hiking for two practical offline-use cases.