Prerequisites
Tutorial 1: Pinpointing location through visual clues: shadows, architecture and terrain.
01
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. The timestamp field in a video file is not a verified record of when the event occurred. Chronolocation is the process of establishing that 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 the angle and direction of shadows to establish time of day and, in combination with a confirmed location, to narrow the date window. Historical satellite imagery compares features visible in the footage against dated archive passes to establish a latest-possible and earliest-possible date. Weather archive cross-reference matches observable conditions in the clip against METAR records for the confirmed location. Used together, these three methods can 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 the verification capacity of most newsrooms. AI-generated video is now indistinguishable from genuine footage under casual inspection. A chronolocation finding is not a claim about who filmed something or why. It is a statement about when, derived from physics and the historical record, cross-checked by at least two independent methods. That is the level of rigour required before footage enters a published account.
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 and the Bellingcat network, 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 · peabodyawards.com/award-profile/anatomy-of-a-killing
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
This tutorial is for Signal subscribers.
Methods goes deep on a single technique each fortnight. The decision framework, the tools, the failure modes, and the evidentiary standard required to use the finding defensibly.
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