The BBC's new investigative unit, Africa Eye, published a detailed breakdown of its latest project last week, showing how open-source investigators verified a video from sub-Saharan Africa that had gone viral on social media.

Using a variety of freely available tools, staff at the broadcaster were able to verify that the footage, which showed two women and their children being killed by a group of soldiers, took place in Cameroon – a claim initially stated as 'fake news' by the Cameroonian government.

"We looked at the video and thought there would be enough information in it to find out at least where it happened," said Daniel Adamson, series producer of Africa Eye, who explained that his team worked with a group of independent open-source analysts online.

"I think by its nature, open-source work is very collaborative, and there is a whole community of open-source analysts out there who have expertise in geolocation, weapons analysis, vehicle tracking and many other areas."

After a tip off, the analysts were able to use tools such as Google Earth and Sentinel Hub to pair the mountain's ridge line in the footage to the topography of Northern Cameroon. Satellite imagery also helped them to match landmarks on the ground, confirming the location of the crimes to an area just outside the village Krawa Mafa.

The change in architecture on the ground and the position of the sun during the video, which was analysed using Suncalc, showed that the crimes took place between 20 March and 5 April 2015.

Facebook Graph search tools from the open-source intelligence training guide OSINT helped the team identify the soldiers in the video, who were carrying weapons and wearing uniforms previously seen in Cameroon on an old Channel 4 news report.

"We didn't visualise it on a wall chart or anything, most of the work was done on WhatsApp groups, Slack channels and closed Twitter groups," he said.

"But it didn't become confusing because we had a very clear structure for the investigation, which went back to basic journalism – we asked ourselves: Where did it happen? When? Who was responsible?"

So, how do you get started yourself with open-source investigations?

Aliaume Leroy, open-source investigative journalist at Africa Eye, explained there are a lot of tool databases and kits available online, such as Bellingcat's Online Investigation Toolkit, OSINT Framework and Week in OSINT.

These collaborative platforms and resources are a great way to stay on top of what is new, and discuss any issues with other analysts.

"This is an environment that is moving very fast and there are a lot of new tools and techniques coming out all the time," Leroy said.

"And if you have a passion, get on Twitter and start following the people that use these tools on a daily basis."

Here is a list of people Leroy has recommended to get started:

Are you using open-source tools and investigative techniques for your latest project or story? Let us know @journalismnews

We will be closely following the in-depth reporting at Africa Eye, which was set up as a result of additional funding giving by the government in 2015, producing programmes that hold power to account.

"Everybody from rural Cameroon to Syria has a mobile phone camera in their pocket and there are thousands of videos being uploaded everyday, showing serious wrongdoing or even atrocities," said

"So it is essential that the media has tools and methodologies for verifying and analysing these videos with rigour, and for explaining to their audiences how they did that.

"It's something that goes alongside traditional 'boots on the ground' journalism – open-source techniques are a complement to traditional journalism methods not a replacement."

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