What this app does, and what it doesn't.
WhereAmI shows your live position: latitude, longitude, altitude, speed, heading and accuracy, as reported by your device's GPS or location system. It also translates your coordinates into a readable address (street, postcode, town, region, country).
The position calculated by your device stays on your device. What gets sent, to whom, and when, is explained on the dedicated Privacy page.
Once installed on your home screen, the app loads without a connection thanks to a service worker that keeps its files cached. Only the features that query a third-party service (address, altitude, points of interest) need an active connection.
GPS doesn't measure your horizontal position and your altitude with the same reliability. Horizontal position (latitude/longitude) relies on at least 3–4 satellites spread around you, and commonly reaches an accuracy of a few metres once the signal has settled. Altitude, on the other hand, also depends on satellites positioned above you — a less favourable geometry, especially in valleys or near terrain — and its error is typically 2 to 3 times larger than that of horizontal position.
In practice, it's not unusual for a smartphone's GPS to report an altitude around fifty metres higher than the one shown on official topographic surveys or elevation markers. That's exactly why WhereAmI lets you compare GPS altitude against the altitude calculated by Open-Elevation from terrain models.
Map, address and points-of-interest data come from the OpenStreetMap project and its contributors, under the ODbL licence. Compared altitude data comes from Open-Elevation (SRTM). See the legal notice for details on limitations and liability.