Geolocation

What it does

Geolocation puts your position on the map, using the browser's location service. It draws a marker and an accuracy circle. The circle matters: a location fix is an estimate, not an exact point.

Track me keeps receiving location fixes and joins them into a trail. Tracks are stored in the browser between sessions. Each tracking session is a separate track.

A stored track can be added back to the map (Add to map), saved as files (Save as files), or deleted (Erase from memory). Saved tracks include both a line and the individual points with their accuracy.

Location fixes can be noisy. The tool filters unlikely jumps against recent speed, so standing still does not produce a long trail and one bad fix does not become a sharp corner.

Nothing here reaches the network. Position comes from the browser, tracks are stored in this browser, and the export is a local download.

Using it

1. Open the tool. The browser asks for permission in a prompt of its own. Allow it. The permission belongs to the browser, not to the map, so a refusal cannot be worked around from here, only granted again.
2. Your position appears with its accuracy circle. A large circle means the device is unsure. This can happen indoors, or without a satellite fix. It does not mean the map is wrong.
3. Turn on Track me to record a trail. Close the panel and tracking keeps running. The map does not have to stay in front of you.
4. Open a stored track to add it to the map, save it, or erase it.

Two things can stop geolocation before it starts, and both look the same from inside the page. The browser reports Permission denied, code 1 either way:

• The page is not on a secure origin. Browsers hand out location only over https://, or on localhost while you are developing. A map served from a plain http:// address is refused before the prompt ever appears, so there is nothing to allow. Serve it over HTTPS.
• The prompt was dismissed or blocked. Browsers remember that answer and stop asking, so reloading changes nothing. Reopen the permission from the padlock or the location icon in the address bar and set this site back to Allow.

If the browser has no location service, the panel says so.

Accuracy varies by device and surroundings far more than by anything the map can do. A phone outdoors gives metres. A desktop over Wi-Fi may give the city.

In your own map

Add geolocation to a toolbar. The behavior is tunable through attributes on the element:

• watch: keep following the position rather than taking a single fix (default on).
• high-accuracy: ask the device for a more accurate fix, at a cost in battery (default on).
• timeout and max-age: how long to wait for a fix, and how old a cached one may be.
• follow: keep the map centered on the position as it moves.
• zoom: the zoom to use when the map moves to a fix.

Serve the map over HTTPS. Browsers give location only to a secure context: https://, or localhost while developing. A plain http:// host is refused with the same permission error as a denied prompt.

Extending it

Position state is shared across instances on a page, so two geolocation controls do not open two location watches or draw two markers.

Stored tracks use one compact array per point: track id, order, timestamp, longitude, latitude, and accuracy. buildTrackGeoJSON turns them back into the point and line collections used by the map and export.

Change the plausibility rules only with recorded tracks to test against. They scale by a moving average of recent speed, so the same jump may be valid in a car and invalid while standing still.