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Flight Data and Updates
Those moving dots on the radar are driven by real flight data — but where it comes from, how often it refreshes, and how the aircraft keep gliding between updates are worth understanding. This page covers all three.
Blipscope can pull aircraft positions from either of two sources, chosen with the Data source setting on the Configuration Reference page:
| Source | What it is | Update rate | Daily limit |
|---|---|---|---|
| OpenSky Network (default) | A free public ADS-B service in the cloud. No extra hardware — works out of the box. | A few minutes to ~20 s (see below) | Yes |
| Your own ADS-B receiver | A receiver on your own network — e.g. a Raspberry Pi running dump1090-fa, readsb, PiAware, or tar1090. | About once per second | No |
Both feed the same radar. The only differences are how fresh the data is and whether there's a daily cap.
OpenSky is free and works with or without an account, but it caps how much data you can pull per day:
| Account | Daily allowance |
|---|---|
| Anonymous (no account) | 400 credits |
| Registered (free account) | 4,000 credits |
| Active feeder (you also feed data to OpenSky) | 8,000 credits |
⚠️ These are credits, not simple request counts. A single request costs between 1 and 4 credits depending on how large an area you ask for:
Area requested Credits per request up to 25 square degrees 1 25–100 square degrees 2 100–400 square degrees 3 larger / whole world 4 Blipscope only ever asks for a small box around you — at most about 2° in each direction, well under the smallest tier — so every refresh costs exactly 1 credit. For Blipscope, then, the daily credit allowance is effectively the number of updates you get per day.
Blipscope spreads its daily allowance evenly across 24 hours so it never runs out before the day is up. At one credit per refresh, that works out to roughly:
| Account | Radar refresh |
|---|---|
| Anonymous | about once every 3–4 minutes |
| Registered | about once every 20 seconds |
So a free OpenSky account isn't just a bigger number on paper — it makes the live view roughly ten times more current. Creating one takes a couple of minutes; see Network and Setup.
If OpenSky only refreshes every few minutes, why do the planes glide smoothly across the radar the whole time?
Because Blipscope predicts each aircraft's position between updates. Every contact reports not just where it is, but its heading and speed. Between refreshes, Blipscope advances each one along its last known heading at its last known speed — recalculated many times a second — so the dots drift continuously, no new data required. It's the same "dead reckoning" that ships and aircraft have navigated by for centuries.
When a real update finally arrives, Blipscope doesn't snap the aircraft to its new spot — it eases smoothly from where the dot currently is to the freshly reported position, so corrections look like natural motion rather than jumps.
📌 The trade-off: between updates, the on-screen position is an estimate that assumes the aircraft keeps flying straight and steady. That's spot-on for a cruising airliner, but if a plane turns or changes speed, Blipscope won't know until the next refresh — so on anonymous OpenSky (a few minutes between updates) a manoeuvring aircraft can visibly "correct" itself when fresh data lands. A registered account, or your own receiver, shrinks that window and keeps the picture much closer to reality.
If you run your own ADS-B receiver, pointing Blipscope at it removes the daily limit entirely and refreshes about once a second — the smoothest and most accurate option, and it keeps working even if OpenSky is unavailable. The altitudes and speeds your receiver reports (in feet and knots) are converted automatically so the display matches everything else. See Network and Setup for how to switch the Data source to your receiver and enter its address.
- Network and Setup — OpenSky accounts, and pointing Blipscope at your own receiver
- Configuration Reference — the Data source, radius, and OpenSky settings
- Radar Display — what the moving markers mean