Dating video: solar geometry, satellite, weather archive

Block

01 · Geo & Chrono

Topic

Chronolocation

Tools

SunCalc · Google Earth Pro · Meteostat

Difficulty

Intermediate

Prerequisites

Pinpointing location through visual clues: shadows, architecture and terrain.

See also: Image geolocation: methodology and workflow (GEO-001) for the full satellite and street-level triangulation workflow this tutorial assumes.

A timestamp is not evidence. A chronolocation is.

Footage of an alleged atrocity, a product being tested, a military convoy moving: the clip surfaces online and the timestamp reads whatever the uploader chose to type. Chronolocation is the process of establishing a real record, using observable physical evidence within the footage itself to fix when it was recorded, independently of any metadata the source controls.

This tutorial covers three methods. Solar geometry reads shadow angle and direction to establish time of day and narrow the date window. Historical satellite imagery compares footage features against dated archive passes to bound a filming date. Weather archive cross-reference matches observable conditions against METAR records for the confirmed location. Used together, they produce a defensible date range, or in favourable conditions, a specific date and time.

The volume of footage circulating during armed conflict, protest and humanitarian crisis has outpaced newsroom verification capacity, and AI-generated video is now indistinguishable from genuine footage under casual inspection. A chronolocation finding is a statement about when, derived from physics and the historical record, cross-checked by at least two independent methods.

In the field

In July 2018, video of an extrajudicial execution circulated on social media. The Cameroonian government dismissed it as fabricated. BBC Africa Eye, working with Amnesty International, used open-source methods to establish that it was genuine, that it took place in Cameroon's Far North region, and that it was filmed in early 2015.

Solar geometry. Shadows cast by soldiers moving along a track were measured for angle and direction. Applied to the confirmed location via solar calculation, the team established the filming window as between 20 March and 5 April 2015.
Historical satellite imagery. A building visible in the footage appeared intact. Satellite archive imagery showed it had been demolished by February 2016, establishing the latest possible filming date.
Contextual cross-reference. The two findings were consistent and mutually reinforcing, narrowing the date window to a specific fortnight in spring 2015.

BBC Africa Eye · Anatomy of a Killing · 24 September 2018

Learning outcomes

By the end of this tutorial you will be able to:

Read shadow angle and direction in a video frame and calculate a time-of-day range using SunCalc
Navigate Google Earth Pro's historical imagery archive to bound the earliest and latest possible filming date
Retrieve and read METAR weather records to cross-reference observable conditions against a candidate date range
Combine the three methods into a defensible chronolocation entry in your investigative dossier
State the confidence level of your finding and the conditions that would change it

The rest of this tutorial is for Signal subscribers.

What remains: the decision framework, the tool configuration, the failure modes, and the evidentiary standard required to use the finding defensibly. Signal is €90 a year, or €9 a month. Students, €49 a year.

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Chronolocation video: establishing when footage was filmed

A timestamp is not evidence. A chronolocation is.

Learning outcomes

The rest of this tutorial is for Signal subscribers.

A Signal subscription gives you:

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