Introduction
Transit Chaser combines real-time or near-real-time aircraft data with Sun, Moon, location, and geometry calculations to estimate possible photographic opportunities. These may include aircraft crossing the Sun or Moon, aircraft passing near each other from the observer’s viewpoint, high-altitude contrail opportunities, and selected aircraft-watch modes.
The app may use different data sources depending on the selected mode, provider availability, user settings, provider limits, and technical configuration. Live aircraft position requests are routed through Transit Chaser backend routes where practical, so request volume can be controlled and providers are not hit directly by every visitor browser.
Data providers can change their terms, data formats, rate limits, access rules, pricing, or availability at any time. If a provider changes or blocks access, Transit Chaser may partially or completely stop working until the app is updated.
1. Current Standard Live Source
Transit Chaser currently routes its standard live aircraft-position requests through a Transit Chaser backend route and uses adsb.fi as the current standard community ADS-B source.
This backend route is used so Transit Chaser can keep provider access controlled, avoid browser CORS issues, and adjust caching, request limits, attribution, or access controls if required.
2. Airplanes.live
Airplanes.live is a community ADS-B data network that may be supported by Transit Chaser only where access is available and permitted by Airplanes.live.
If Airplanes.live access is approved or available, Transit Chaser intends to route requests through its own backend where practical, follow any limits set by Airplanes.live, and display appropriate attribution.
Key Links:
- Airplanes.live Homepage
- Airplanes.live API Guide
- Airplanes.live Data Field Descriptions
- Airplanes.live Terms of Service
Transit Chaser does not own Airplanes.live data and cannot guarantee access. If Airplanes.live becomes unavailable, rate-limited, blocked, or changes its rules, affected Transit Chaser features may stop working unless another permitted source is available.
3. ADS-B Exchange
ADS-B Exchange is an aircraft-data provider that may be used as an optional mode in Transit Chaser. Access may require a user-supplied API key, RapidAPI account, paid plan, or other credentials depending on the selected method and current ADS-B Exchange access rules.
ADS-B Exchange can provide real-time aircraft position data, callsigns, aircraft type information, altitude, speed, heading, and other aviation data fields where available.
Key Links:
- ADS-B Exchange Homepage
- ADS-B Exchange Data Products
- ADS-B Exchange API Lite / Personal Use Information
- ADS-B Exchange on RapidAPI
If you enter an ADS-B Exchange or RapidAPI key into Transit Chaser, that key is used only for your selected provider request. You are responsible for complying with ADS-B Exchange, RapidAPI, and any related provider terms, quotas, pricing, and rate limits.
Transit Chaser does not own ADS-B Exchange data and is not responsible for ADS-B Exchange access changes, billing, rate limits, outages, or account restrictions.
4. OpenSky Network
OpenSky Network has historically been supported by Transit Chaser as a flight-data source. Depending on current app settings and OpenSky access rules, this may be a legacy, optional, limited, or unavailable mode.
OpenSky provides aircraft state vectors and related information such as position, velocity, heading, altitude, callsign, and timestamps where available.
Key Links:
Transit Chaser does not own OpenSky data and cannot guarantee OpenSky availability, compatibility, or access.
5. Sydney Airport Schedule Data
Transit Chaser may use Sydney Airport schedule data or related public schedule information for features such as Big Planes mode. This type of data is different from live ADS-B aircraft tracking. It may show scheduled or estimated arrivals and departures rather than exact live aircraft positions.
Schedule data may be delayed, changed, cancelled, incomplete, or unavailable. It should be treated as a helpful planning guide only.
Key Link:
Transit Chaser does not own Sydney Airport data or airline schedule data and cannot guarantee accuracy or availability.
6. SunCalc and Celestial Calculations
Transit Chaser uses SunCalc and related calculation logic to estimate Sun and Moon positions from the observer’s location and time. These calculations are combined with aircraft data to estimate possible visual alignments.
Key Link:
SunCalc is an open-source library. Transit Chaser’s prediction logic may also include additional custom geometry, projection, margin, and filtering code. These calculations are estimates only and may contain mistakes or limitations.
7. Why Multiple Sources May Be Supported
No single flight-data source can guarantee perfect global coverage, live accuracy, unrestricted access, unlimited request volume, and permanent availability. Aircraft data depends on many factors, including receiver coverage, provider infrastructure, aircraft equipment, data-sharing rules, API limits, and provider policies.
Transit Chaser may support additional sources only when access is explicitly configured and permitted:
- Coverage: If one source has poor receiver coverage in a region, another source may perform better.
- Data fields: Some sources may provide aircraft type, registration, heading, altitude, or callsign more reliably than others.
- Feature support: Some modes need live aircraft positions, while others may use schedule-style data.
This does not mean Transit Chaser owns or guarantees the data. All provider data remains subject to the relevant provider’s own terms and technical limits.
8. Responsible Use
Transit Chaser is built as a free community effort for photographers and sky watchers. To help keep the app usable and respectful of data providers, users should avoid excessive use.
Please do not:
- Scrape or bulk-download aircraft data through Transit Chaser;
- Use bots, scripts, or automated tools to repeatedly hit provider APIs;
- Try to bypass rate limits, blocks, provider rules, or access restrictions;
- Leave the app running unnecessarily for long periods if you are not actively using it;
- Use Transit Chaser as a substitute for official aviation, airport, weather, drone, or safety information.
Transit Chaser may include features such as controlled refresh intervals, session pauses, backend routing, warnings, or temporary provider disablement to reduce unnecessary load on third-party services.
9. Accuracy and Availability
Flight data can be delayed, wrong, incomplete, missing, duplicated, or unavailable. Aircraft may turn, climb, descend, slow down, speed up, or disappear from a feed. Receiver coverage may vary by location. Some aircraft may not transmit public ADS-B data, may be filtered, or may not appear in a provider response.
Transit predictions can also be affected by observer location, elevation, timing, internet delay, browser behaviour, map selection, celestial calculations, aircraft altitude, aircraft heading, prediction window, detection margin, and other factors.
For these reasons, Transit Chaser cannot promise that an alert, prediction, direction, flight number, aircraft type, altitude, or alignment is correct.