Ephem · overhead map
Which satellites are over you right now?
Point-in-time view of the low-earth-orbit population above your address. Grant geolocation (or search for a city) and Ephem shows the next five overpasses for each major broadband constellation, plus everything currently above the horizon.
§1 How it works
Ephem downloads the CelesTrak two-line-element sets for each provider (cached at the edge, one HTTP request each), propagates them in your browser with the open-source SGP4 implementation from satellite.js, and plots the sub-satellite points on OpenStreetMap tiles. No account, no cookies, no server round-trip per pass calculation.
§2 Providers currently tracked
| Provider | Operator | Nominal shell | Notes |
|---|---|---|---|
| Starlink | SpaceX | 550 km | Low-earth-orbit constellation operated by SpaceX. ~5,000 active satellites, ~550 km shell. |
| OneWeb | Eutelsat OneWeb | 1,200 km | LEO broadband constellation, ~1,200 km. Enterprise + government focus after Eutelsat merger. |
| Iridium | Iridium Communications | 780 km | Cross-linked LEO constellation, 66 active + spares, pole-to-pole coverage at 780 km. |
| Viasat | Viasat Inc. | 35,786 km | Geostationary broadband operator; incorporates the former Inmarsat fleet. |
§3 Static overpass tables
The interactive map is convenient, but a plain-HTML page for each major city is what indexes well and what nomads open on 3G. Browse /overhead/{country}/{city} for any of 150 seed cities.
§4 Contribute a speedtest
Anonymised readings feed a public per-provider heatmap at /v1/speedtest/heatmap. Location is used to a 2° grid cell; nothing is tied back to your account (there is no account).
Idle.
§5 Editorial position
Ephem does not accept referral fees to promote one provider over another. The affiliate links on /coverage/starlink and its siblings are disclosed on each page. They exist because the map's hosting is free but the operator's time is not, and because sending a nomad to a working sign-up flow is materially useful. If a provider withdraws from public availability, they come off the map.