MANAUS, July 29 — Hundreds of hidden structures have been identified beneath the Amazon rainforest, lifted from obscurity by a technology that sees through the canopy. The tool is lidar – light detection and ranging – and it has become as indispensable to tropical archaeology as the trowel.
Under the hood, lidar works by firing pulsed laser light from an aircraft at the ground, hundreds of thousands of pulses per second. The returning signals measure distance with enough precision to map the bare earth, stripping away the dense vegetation that has concealed human activity for centuries. What emerges are digital elevation models, and from those, archaeologists can pick out the tell-tale signatures of mounds, roads and earthworks.
The technical reality is that this is not magic – it is careful data processing and validation. Lidar surveys cover vast areas – tens of thousands of square kilometres – in a fraction of the time ground teams would need. But as ever, what the sensor reveals must be ground-truthed. Natural features can mimic anthropogenic ones, and sorting one from the other requires on-site verification.
A Brief History of Lidar Archaeology
Lidar has been used in Mesoamerica since the early 2000s. Its most celebrated early success came in 2009, when it revealed the ancient Maya city of Caracol in Belize – a discovery that rewrote the map of Maya urbanism. In the Amazon, the technology has gradually peeled back the green curtain: geoglyphs in the Brazilian state of Acre were first documented using lidar in 2018, and extensive pre-Columbian settlements have been mapped in the Llanos de Mojos region of Bolivia.
The new survey – the one that has just uncovered hundreds more hidden structures – is consistent with that trajectory. The exact extent of the study area has not been disclosed, so the detail that matters is that multiple sites were likely covered. The cost of such work is not trivial: between $200 and $500 per square kilometre, depending on resolution and logistics. For a survey covering tens of thousands of square kilometres, that adds up.
Standard Tool, Broad Applications
Lidar has become a standard tool in tropical archaeology, but its uses extend well beyond the discipline. Forestry services deploy it to measure canopy height and biomass. Urban planners use it for flood-risk modelling. Disaster management teams rely on it to assess damage after earthquakes or landslides.
For now, though, the Amazon story is the one that captures the imagination. Hundreds of structures, hidden for centuries, are now visible in the data. The next step – ground-truthing, excavation, analysis – will take years. But the technology has already done its essential work: it has shown us what we were missing.
