Lidar Reveals Ruins of Lost City

An airborne laser mapping project involving billions of laser shots has unveiled archaeological ruins in a remote region of Honduras that may contain the legendary lost city of Ciudad Blanca, or White City.

Scientists from the University of Houston and the National Science Foundation’s National Center for Airborne Laser Mapping (NCALM) successfully completed the first light detection and ranging (lidar) survey of part of the country’s Mosquitia region, one of the least-explored virgin rain forests. Initial analysis of the survey identified ruins that could be those of Ciudad Blanca or other long-hidden sites.

A 3-D surface map showing geometrical "rectangular" elevated features along the perimeter of the depressed rectangular shape seems to indicate unnatural rather than natural features. (Images: National Center for Airborne Laser Mapping/University of Houston)

In 1544, the Bishop of Honduras wrote to the King of Spain about a large city in one of the river valleys that cut through the Mosquito Coast, where nobles ate from plates of gold. Since then, the legend of Ciudad Blanca has continued to grow. It is sometimes credited as the birthplace of the Aztec god Quetzalcoatl, and travelers have occasionally reported deep-jungle sightings of a large city with elaborately carved white stones.

The Honduras mapping project was initiated by UTL Scientific LLC, a group formed by principals of the Honduran lidar survey project. UTL project leader Steve Elkins had been fascinated by this rain forest region since his first visit more than 20 years ago, but poor satellite image technology had hindered him from being able to unearth what is under the thick forest canopy.

Elkins contacted researchers at UH, NCALM and Geosensing Systems Engineering to overcome this obstacle.

Graphic image of a small section of La Mosquitia rain forest in Honduras using X-Y-Z coordinates derived from lidar observations.

For more than a decade, UH scientists have worked to refine and apply airborne lidar to unveil Earth’s surface, primarily for scientists researching processes that create landscapes. In 2009, using airborne lidar, UH researchers and a field team successfully mapped the Caracol archaeological site in Belize. Although covered with dense rain forest, the team captured building ruins and agricultural terraces not discovered by archaeologists working on the ground for more than 25 years.

For the Honduras project, the team blanketed the area with 25 to 50 laser pulses per square meter — a total of more than 4 billion laser shots. Areas were mapped, and the images collected were reduced and filtered to remove vegetation to provide “bare earth” digital elevation models in near-real time in the field. These models were used to produce geodetic images of the terrain’s surface below the rain forest, and those images were searched by eye to study geomorphological features and potential archaeological ruins.

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