Lake Volta, in the eastern part of Ghana, has long been a center of endemic child slavery: trafficked children are abducted from their homes and employed in the local fishing industry, where they are exploited, working up to 19 hours a day performing hard and dangerous tasks.
There are relief organizations that want to help put an end to these practices. But it’s hard to tackle a problem when you don’t know how big it is. According to the International Labor Organization (pdf, p.22), an estimated one-third of the 1.2 million child laborers in Ghana are located in the Volta region. How many are currently employed in fisheries is harder to pinpoint.
Martina Ucnikova, an executive for the Global Fund to End Slavery, tells Quartz that given how large the lake is—8,502 square kilometers (nearly 3,380 square miles)—it’s difficult to get an accurate count of all theboats, buildings, and fish cages that have sprung up in, on, or around the lake.
There is, however, a relatively easy way to scan the lake for signs of fishery—looking from high above, through a satellite image. This is why the Global Fund to End Slavery partnered with Tomnod, a crowdsourcing research project that makes high-resolution satellite images provided by satellite company DigitalGlobe (of which Tomnod is part) available online.