Use the ‘find my location’ button to jump directly to your location (pictured by a target symbol, shown in the bottom right corner). This will use the GPS signal to find your location as accurately as it can. If your device does not have a GPS chip, if GPS is disabled or there is no signal (such as in a building or near tall cliffs) this will not work. While the icon is highlighted, the map will centre on your location.
OS Maps uses the location as provided by your device. Ensure that the location settings are turned on, and the app has permission to access them. On some devices, you will need to allow OS Maps to access location at all times. This is to ensure that when following a route, your location is kept up to date, even if you close the app, open another app or turn the screen off.
If the device is unable to show the exact position, it may show an approximation based on the nearest mobile phone mast, WiFi access point or last known position. For some devices, you can force it to only show the position from the GPS chip by going into Phone settings > Location > and setting it to GPS only.
If a clearly incorrect location is shown, often waiting a few moments or tapping the 'locate me' on and off will force the device to update your location.