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3000 acres of lidar exploration: Mapping Palau's hidden terraces

Updated: 2 days ago

What are Palau's dense jungles hiding underneath them? Follow along as drones equipped with LiDAR sensors unearth hidden structures and history.


DJI M350 RTK equipped with the L2 sensor Flying over Aimeliik State
DJI M350 RTK equipped with the L2 sensor Flying over Aimeliik State

Snapshot

2cofly (E-co-fly) is a leading drone service provider in Guam and Micronesia. Since 2021, they have conducted small to large-scale missions in various industries such as construction, engineering, renewable energy, insurance, archaeology, and more.


2cofly conducted a large-scale LiDAR scan of the state of Aimeliik in Palau over a two-week period to produce a bare earth model for archaeological analysis and study. Funding for the “Preserving the Legacy of a Monumental Earthwork Landscape Project in Palau” is provided by the U.S. Ambassadors Fund for Cultural Preservation.


Packing Up

2cofly took a two-week trip to Palau, scanning over 3,000 acres of land to help uncover Palau’s archaeological secrets. Palau’s rich oral history says nothing of the extraordinary terraces that span many states, yet passersby can immediately notice these terraces once they see just one of them. If they are so easily noticeable, why is there no history about them? With that question in mind, 2cofly packed up all their equipment and set off for Palau.



Aerial view of one of the many terrace that can be seen
Aerial view of one of the many terrace that can be seen

Kick Off

On the first day, we met with the clients for a kickoff briefing to get more information about the project and the end purpose of our work. The work is supported by a US Ambassadors Fund for Cultural Preservation awarded to Coral Reef Research Foundation and Dr. Jolie Liston. The main person interested in the data we were collecting over the next 12 days was the lead archaeologist, Dr. Jolie Liston. She is the resident archaeologist in Palau, contributing to many notable projects such as The Compact Road. Dr. Liston gave a presentation to the 2cofly team (Thomas, Dong, Anthony) on the significance of these terraces.


She explained that there are no oral records mentioning these terraces, and her research revealed that these terraces were not just used for agriculture like those in Asian countries, but were actually cities! These terraces were intricate networks of large-scale civil engineering and architectural feats, involving the movement of tons of earth to create raised living areas that are still visible today. If you travel through Palau and look out into the vast greenery, you’ll spot these marvels. However, Dr. Liston knew there were many more terraces still hiding under the trees and overgrown ferns, and that’s where 2cofly stepped in.


           Flight Planning using Google Earth                       One of the many processed areas using DJI terra software
Flight Planning using Google Earth One of the many processed areas using DJI terra software

LiDAR

Jolie had already known there were many more terraces out there in Palau from a LiDAR scan done by the military. However, she wasn’t satisfied with the data as it was too pixelated in some areas due to being flown from such a high altitude. 2cofly, using drone-mounted LiDAR sensors, can fly at sub-200 feet above the ground, not only collecting more points on the ground but also providing better resolution to clients. With all the presentations out of the way and knowing what was expected to be found in these scans, we set out to do a site visit of the areas.


Processed LiDAR Data near Tarzan Pools hike, Guam
Processed LiDAR Data near Tarzan Pools hike, Guam

What is LiDAR

Lidar, which stands for Light Detection and Ranging, is a technology that uses laser light to measure distances. A lidar system sends out pulses of laser light. These pulses bounce off and return to the sensor. The system measures the time it takes for the light to return. By calculating the distance based on the travel time of the light, lidar creates a detailed 3D point cloud of the environment. This includes precise measurements of the shape and surface features of objects.


From Left: Anthony Herman, Thomas Torres II, Dong Lee, Jolie Liston
From Left: Anthony Herman, Thomas Torres II, Dong Lee, Jolie Liston

Site Visits

The proposed area for our 3,000-acre scan, and where we would be working for the next 12 days, was the state of Aimeliik. As with all our other missions, we did site visits to identify potential issues that we couldn’t foresee in our planning stage using Google Earth. The heavy fog and dark gray clouds were just one of the many factors we would face, as seen in the picture above. Along the way, we noted many environmental challenges that needed to be overcome, such as connectivity issues with the drone flying around a large hill, variable terrain heights, and more that had to be addressed once flying. After all the site visits, we headed back to our Airbnb to debrief and plan for the coming days, knowing the new factors we would face.


Leica and DJI RTK base station setup on one of the locals farmland. DJI RC Plus controller with a Side by Side view of the LiDAR capturing data Anthony Herman standing among the foliage  for better observation of the drone

Days 2-6

Throughout the next 11 days, it was a continuous cycle of setting out ground control points, capturing the points for georeferencing for accurate data renderings, and flying missions. Rain or shine, we continued this cycle until the end of the trip. Using two drones equipped with the L2 sensor made this trip go much smoother, as the original plan was to use one drone to map out the many sites.


Collection of different gcps, from mesh, painted, and custom made ones

Mountain Hikers

Day’s 7 and 8 we started to do the southern polygon which we deemed as the most difficult of the drone scans. Despite the rain and a 2 hour hike…you read that right a 2 hour long  hike one way…with heavy equipment, we completed our mission but not with some hiccups.


Day 2 of the Southern Polygon mission at the entrance of the trail with 2 additional helpers to help with carrying the many cases of equipment's through the jungle
Day 2 of the Southern Polygon mission at the entrance of the trail with 2 additional helpers to help with carrying the many cases of equipment's through the jungle

Day 7 

We navigated with the help of a local hunter through the tough terrain, which was much more difficult than anticipated…Seriously some type of ninja warrior obstacle course… This experience highlighted the importance of site visits to understand physical conditions not visible on Google Earth. In hindsight, scouting alternative launch sites would have been wiser. The location we reached was ideal for a launching  area. However, we faced several issues, including point cloud errors, low water supply, and diminishing daylight. Although LiDAR can operate at night, we chose not to risk navigating the jungle in the dark, splitting the task into a two-day mission.


Day 8

We were much better prepared this time with more water, snacks, and helpers. The weather was ideal, with clear skies and a steady breeze as we would be exposed to the sun for the next five hours of nonstop flying. We finished the mission as expected, and after a successful second day of flying the southern polygon, we trekked back to the vehicles and called it a day.


Day 2 of the Southern Polygon mission at the entrance of the trail with 2 additional helpers to help with carrying the many cases of equipment's through the jungle
Day 2 of the Southern Polygon mission at the entrance of the trail with 2 additional helpers to help with carrying the many cases of equipment's through the jungle

Count Down

Day 9

We started our morning with a 4 hour hike through rivers and running past alligators—No, we did none of that, but there are alligators here though. We had an easy short hill to climb up, but the fatigue from yesterday started kicking in and the weather was having us ground every 30 minutes. We came to a consensus to just call it for a day and take the day off to rest more, and retry this the following day.


Day 10

Feeling much more refreshed we got back to the jobsite. This time it went much better than the previous day. Rain was in the air, but it kept missing us each time it came pouring by. We ended the day pretty late, but we finished! WOOOOOOOO!!…Yeah I would be excited, but I had the lovely task of clean all our mesh pads, and drone equipment's…It was very very very exciting…sigh


Picture of the M350 launching and a local kid helping with battery swaps
Picture of the M350 launching and a local kid helping with battery swaps
GIF of the point cloud rendering in real-time within the DJI RC Plus controller using the L2 sensor
GIF of the point cloud rendering in real-time within the DJI RC Plus controller using the L2 sensor

Count Down

Despite the many challenges faced since day one, we finished this long trip successfully. Drones are providing revolutionary solutions to the archaeological industry, but their benefits don’t stop there. The same is true for all other industries like construction and engineering, and infrastructure management such as solar farm maintenance. The agricultural industry is also seeing major benefits from using drone technology. Drones have an endless amount of use cases; just one simple email or consultation is all you need to see the incredible benefits they can provide.


Aerial photograph with local farmer and family after finished flight
Aerial photograph with local farmer and family after finished flight
 
micronesia's largest fresh water lake

2cofly is a full service drone service provider in Guam and Micronesia. Our company has two primary focus areas: construction and education.


We work primarily with construction and engineering firms and offer:

  • Orthomosaic Mapping (+ Planimetric Mapping)

  • Topographic Mapping (via LiDAR & photogrammetry)

  • General LiDAR Mapping (land feasibility study, power line, etc)

  • Aerial Inspection

  • Aerial Magnetometry (underground metal detection)

  • Part 107 education and drone training

 

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(671) 988-1532

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