SunCalc
Sun position and shadow calculator for chronolocation and photo verification. The standard tool in OSINT shadow analysis.
What should journalists know about SunCalc?
SunCalc is the default shadow-analysis tool in investigative journalism. Set a location on the map, pick a date, drag the time slider — you get sun azimuth, altitude, shadow direction, and daylight phase boundaries. Bellingcat's 2024 Shadow Finder tool uses the SunCalc library (v0.1.3) under the hood, which tells you how foundational this is. The math is accurate. The bottleneck is always the investigator's ability to measure shadow angles and object heights from imagery — SunCalc itself introduces negligible error. Two things to know: suncalc.org (Torsten Hoffmann) and suncalc.net (Volodymyr Agafonkin) are different projects by different developers. Agafonkin's suncalc.net hasn't been updated in 15+ years; he says a new version is coming. SunCalc.org is the actively maintained version with shadow-length overlays, eclipse data, and photovoltaic analysis. Both use Google Maps, which means Google sees every location you search. For sensitive investigations, note coordinates offline and use a non-Google calculator.
Chronolocation — confirming when a photo or video was taken by matching shadow direction and length against sun position. Geolocation cross-referencing when shadow angle narrows candidate locations. Verifying claimed timestamps on conflict imagery (airstrikes, military movements). Planning photo/video shoots around specific lighting conditions.
Overcast conditions — no shadows, no signal. Indoor photos. Images where shadow edges are ambiguous or objects lack clear vertical profiles. SunCalc gives you the theoretical sun position; you still need geometry skills to measure shadow ratios from imagery. If you need 3D terrain shadow modeling, use ShadeMap instead.
Security & Privacy
Data is scrambled while being sent to their servers
Data is scrambled when stored on their servers
Where servers are located — affects which governments can request your data
Privacy policy summary
No account. No login. No data stored server-side. All sun-position math executes locally in JavaScript. The Google Maps tile layer is the privacy exposure: Google logs map tile requests with your IP, location coordinates, and timestamps. No first-party analytics or tracking visible in the source.
How to protect yourself:
Use a VPN when researching sensitive locations — Google Maps tile requests reveal coordinates and your IP. For high-risk investigations, note GPS coordinates from a separate source and use an offline sun-position calculator (NOAA's solar calculator or the Python pvlib library). Cross-reference SunCalc results with Stellarium (offline planetarium software) for independent verification. Bellingcat's Shadow Finder automates the global search that SunCalc requires you to do manually — use it when you have shadow measurements but no candidate location.
Open-source, client-side calculations with no server-side data processing. The sole privacy concern is Google Maps: every location you view generates tile requests to Google's servers, exposing coordinates and your IP address. No account, no cookies, no first-party tracking. Rating stays 'adequate' rather than 'strong' because the Google Maps dependency is baked in with no option to swap map providers, and investigators working on sensitive locations (conflict zones, source locations) should treat those tile requests as a metadata trail.
Who Owns This
Known issues
Agafonkin's suncalc.net site hasn't been updated in 15+ years and he acknowledges it's 'falling apart' — a new version has been promised but not shipped. The npm library (mourner/suncalc) has 3.4k GitHub stars but sees only occasional maintenance commits. SunCalc.org and suncalc.net are separate projects by different developers — easy to confuse. The suncalc library doesn't account for atmospheric refraction at very low sun angles (sunrise/sunset), which can introduce ~0.5° error. Shadow-length measurements from photos are inherently imprecise — accuracy depends on the investigator, not the tool. If you only know the month and year, expect ±15 minutes accuracy on chronolocation estimates.
Pricing
Free. No account required.
This is an editorial assessment based on publicly available information as of 2026-04-02, using our published methodology. Independent security review is pending. Security posture can change at any time. This is not a guarantee of safety.
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