Chasing a Lost City
- 3 days ago
- 4 min read
Exploring the Limits of Aerial GPR at the Lost City of DeMille
Beneath the Sand
Buried beneath the shifting dunes of Guadalupe, California, lies what many refer to as the Lost City of DeMille.
Built in 1923 for the filming of The Ten Commandments, the massive set was abandoned and slowly reclaimed by the landscape. For over a century, wind and sand have erased nearly all visible traces, leaving behind a site that sits somewhere between history and legend.
For archaeologists and researchers, the question remains: What still lies beneath?
For our team, it became a different question.
Can aerial systems help find it?
Traditional archaeological methods can be slow, invasive, and limited in coverage. The goal of this project was to explore a different path, using aerial data collection to scan beneath the surface without disturbing the site.
By pairing the IF1200 drone with ground penetrating radar, the team set out to test whether aerial GPR could provide meaningful subsurface insight across large areas of the dunes.
A New Approach to an Old Problem
Mission Stack
Aircraft: IF1200
Sensor: Zond Aero 500 Ground Penetrating Radar
Integration & Workflow: SPH Engineering
In theory, this approach could unlock a faster, non-invasive method for identifying buried structures, guiding researchers to the most promising locations for potential artifact recovery.
Today, the site is inaccessible without special permissions and any disruption to the site is subject to severe fines and penalties. Thanks to our partnership with the Guadalupe-Nipomo Dunes Center, we were given the access needed to conduct our missions.
The Guadalupe-Nipomo Dunes Center was integral in the archaeological excavations that occurred from 2011-2017 and is the curator of the artifacts that were uncovered. Those artifacts are on display at the Dunes Center at 1065 Guadalupe Street, CA Guadalupe 93434.
In 1923, director Cecil B. DeMille constructed one of the largest film sets of its time in the Guadalupe-Nipomo Dunes for The Ten Commandments. After filming, much of the set was left behind and eventually buried by shifting sands.
Over the past century, portions of the site have been rediscovered through archaeological efforts, but much of the original set remains hidden beneath the dunes.
To support the Dunes Center and further their mission, please visit their website at https://dunescenter.org.
Four Flights, One Objective
Over multiple site visits, the team conducted four separate flight attempts across targeted areas believed to contain buried structures.
Each mission followed a consistent workflow:
Pre-flight planning and system calibration
Controlled flight paths across defined grid patterns
Data capture using the Zond Aero 500 system
Post-processing and analysis of radar returns
From an operational standpoint, the system performed as expected. The IF1200 delivered stable flight, consistent payload support, and reliable execution across each mission.
But the data told a different story.
When the Data Fights Back
Ground penetrating radar relies on signal reflection through subsurface materials. In ideal conditions, it can reveal changes in density, voids, and buried objects.
In Guadalupe’s dunes, conditions were far from ideal.
Located less than a mile from the Pacific Ocean, the site is heavily influenced by coastal conditions. Moisture within the sand, combined with salt content, became the defining variables.
Saltwater and damp sand increase signal attenuation, scattering radar energy and reducing both penetration depth and clarity. Instead of clean subsurface reflections, the data returned diffused and inconsistent signals across the survey area.
Despite multiple attempts and adjustments, the outcome remained unchanged.
The environment was overpowering the sensor.
What the Data Revealed
Data collected across all four missions showed limited subsurface contrast, with signal degradation consistent across the survey area.
Environmental conditions, particularly moisture and salinity, reduced the effectiveness of radar wave propagation, resulting in:
Weak or diffused reflections
Reduced depth penetration
Minimal differentiation between potential structures and surrounding material
What is GPR?
Ground penetrating radar (GPR) uses electromagnetic waves to detect subsurface features by sending pulses into the ground and reading the reflections. It can reveal density changes, voids, and buried objects without excavation.
Performance depends on soil, moisture, and salinity. For this experiment, we used a 500 MHz system due to FCC operating restrictions in the United States.
Lessons From the Sand
Every mission produces results.
Some provide answers. Others provide clarity.
Moisture Changes Everything
In coastal dune environments, moisture can significantly reduce GPR effectiveness. Even when conditions appear dry on the surface, subsurface saturation can impact results.
Salt Compounds the Challenge
Salinity increases signal attenuation, further limiting radar performance in coastal regions.
Not Every Tool Fits Every Terrain
Aerial GPR holds strong potential, but performance is highly dependent on environmental conditions. Understanding those limits is critical.
Platform Reliability Matters
Even when sensor performance is limited, the aircraft must remain consistent. Across all four missions, the IF1200 provided a stable and dependable platform for testing.
Iteration Drives Progress
Each attempt refined the approach, from flight parameters to data expectations. This is how new workflows evolve.
Pushing the Edge of Aerial Archaeology
This mission was never just about finding artifacts.
It was about exploring what’s possible.
Pairing heavy-lift drones with advanced sensing technologies like ground penetrating radar represents a shift in how subsurface exploration can be approached. While this project highlighted the limitations of current methods in moisture- and salt-rich environments, it also reinforced the potential of aerial systems in archaeological and research applications.
Today, it remains experimental.
Tomorrow, it may become standard.
What Comes Next
The Lost City of DeMille is still out there, buried beneath layers of sand and time for over a century.
Located less than a mile from the Pacific Ocean, the site presents a uniquely challenging environment. Salt content and persistent moisture within the dunes likely played a significant role in degrading radar performance, limiting signal clarity and depth.
Future efforts may require different environmental conditions, alternative sensing technologies, or a combination of methods to unlock what remains hidden.
But progress does not rely on success alone.
It is built on understanding the boundaries, and pushing them forward.
Some missions deliver answers.
Others redefine the questions.
Projects like this help define where aerial sensing workflows still need to evolve.
