Charles, quoting the Economist, wrote:

“Engineers at Lockheed Martin, a large American defence contractor, have designed a radar system called FOPEN, short for foliage penetration.”

When I was in Costa Rica, I spent a lot of time working with the archaeology community.

Archaeology in Costa Rica is rather challenging. Due to extensively thick forests and volcanic activity, much is covered. Even if you come across an ancient town, such as the city of Guayabo just outside present day Turrialba, any attempt at systematic excavation is thwarted due to the density of the forest. Archaeology with bulldozers really doesn’t work and then you’d be left with something like a huge clear-cut area.

However around the time I was working there NASA was doing overflights with sophisticated mapping and sensing technologies. Ostensibly the purpose of this was to determine the natural features of the land so the altitude of the land, and not the forest canopy, could be established.

They found some amazing things.

The not only could see under the foliage, they could see under the soil. They happened to discover these strange lines that didn’t correspond to any modern maps. Archaeologists were sent out to dig and were able to determine the cause of the signals: ancient roads. Centuries of foot travel on these roads had sufficiently compacted the soil so that it produced different thermal characteristics than the surrounding terrain.