GPS itself does not consume your mobile-data allowance. A phone receives navigation signals directly from satellites. What can use mobile data are the services around GPS: loading maps, downloading assistance data, uploading a recorded route, geocoding addresses and sharing your position with somebody else.
GPS is one part of the wider group of satellite-navigation systems commonly called GNSS. Your phone's receiver listens to precisely timed radio signals and uses them to estimate its position. Those satellite signals do not arrive through your carrier and are not billed by the megabyte.
This is why a phone can often determine a position without a SIM card and why offline GPS navigation is possible.
A location app may still transfer data for several reasons. Online map tiles must be downloaded. A route-sharing service must upload latitude, longitude, timestamps and other fields. Address lookup can involve a server. Traffic information, satellite imagery, search results and cloud history all require connectivity unless the app has prepared an offline alternative.
Consequently, turning off mobile data may leave the GPS receiver working while the app's map or remote dashboard stops updating.
Phones can obtain assistance information that helps the receiver find satellites and establish a position more quickly. Android may also combine GNSS with Wi-Fi and cellular observations. That supporting network activity is different from the core satellite signals and is generally tiny compared with streaming media or downloading maps.
If minimizing data use is important, the largest savings often come from offline maps and less frequent server synchronization rather than from trying to disable the positioning hardware.
There is no single number for every tracker. A simple coordinate record is small, but total usage depends on update frequency, protocol overhead, retries, additional fields, diagnostics and whether map imagery is being loaded on the same phone. Sending a point every few seconds can produce far more traffic than sending a compact batch every several minutes.
For a dedicated analysis of this question, see How much mobile data does GPS tracking use?.
Yes. Disabling data roaming does not inherently switch off the GNSS receiver. The phone can still calculate a local position, but a live online tracker cannot upload through mobile data until another internet connection—such as Wi-Fi—is available. This can be useful when travelling internationally and avoiding roaming charges.
Read GPS tracking abroad without roaming for a practical travel setup.
LocationOf needs internet connectivity when location records are being transferred to the website for remote viewing. The positioning process and the upload process should not be confused. During a temporary network gap, locally recorded positions can be useful only if the application preserves them and synchronizes them later.
If you are trying to build a low-data setup, test a real journey and inspect Android's per-app data-usage screen afterward. Your own device and tracking interval provide a more useful answer than a universal marketing estimate.
Not necessarily. The satellite receiver can still work, but the phone loses some network assistance and Wi-Fi/cellular context, so the first fix can take longer in difficult conditions. The effect is not the same as switching the GPS receiver off.
The Android Location switch merely allows location-capable services to operate. Actual network use depends on which apps are active and what they transmit. Check Android's per-app data statistics if you want to know what a particular tracker transferred.
Yes, if delayed synchronization is acceptable and the app supports it. A phone can record away from Wi-Fi and upload when it reconnects. For real-time remote viewing while travelling, some internet path is required.