DEVICE CHECK · 20 TRIALS
Altitude diagnostic
Compare the altitude reported by your browser with a separate terrain sample.
Your location stays on this device until you choose a terrain test
The first button asks the browser for one location fix. It stays in this page's memory. Each terrain test sends that fix's coordinates through this Worker to OpenTopoData to request its srtm30m terrain elevation. Provider requests are spaced at least one second apart.
This app does not save coordinates or results on its server. Results stay in page memory and disappear when you close or reload the page. OpenTopoData handles its requests under its own policy.
01 · DEVICE LOCATION
Check browser sensors
Location permission is requested only after you press this button. This one-time warm-up is excluded from the 20 terrain trials; its timestamp is recorded as a reference.
Waiting for you to start.
These are separate source readings. This diagnostic does not infer a vertical datum for the browser value or convert either value.
02 · TERRAIN REQUESTS
Measure 20 sequential trials
Each request asks the browser for a high-accuracy fix with its cache disabled. The browser or operating system can still reuse a measurement, so the exact location timestamp and its age are recorded. Repeated timestamps are flagged. This is a 20-request timing check, not a statistical independence or GPS-accuracy test.
The gate requires at least 19 of 20 complete terrain trials to finish within 10 seconds each.
No terrain requests have been sent.
| # | Result | Altitude | H. acc. | Fix age | Location | Terrain | Total |
|---|
The visible summary omits coordinates. The downloaded JSON includes precise coordinates, browser timestamps, and source readings for local inspection. Nothing is written to browser storage. A stop request prevents the next trial and cancels an active terrain request when possible.