Mapping Extreme Topography in Death Valley
A larger company subcontracted Altavian to survey at historical Ryan Camp in Death Valley. The company had reservations about being able to collect data in the steep crevices and on the huge rock faces. Even just flying the rugged, desert location would be a challenge. Altavian’s operators analyzed the project and identified the Nova F7200 as the best outfitted drone to complete the project. The Nova, as a sturdy and stable platform, would accurately collect data in the challenging operation area. We could then process the data to produce a colorized 3D point cloud. This point cloud would serve to generate an accurate and detailed topographic base map for the mine’s use.
Although the area could easily be covered in a single flight, the mesa proved to be an especially complex challenge for our drones. The operation department spent an entire week going over every inch of the site before deploying, looking for any potential problems. Our goal was to gauge the overall slope and heights on site and plot our launch and landing zones. The smoothing effect in Google Earth can give false visuals making it difficult to appreciate the actual size of large geologic features.
This process of looking over new flying sites before arriving is a common practice for Altavian operators. Spending office time looking over site features, planned flights, and anticipating hang-ups reduces the time wasted on-site. For this job, however, we needed to scale up our normal processes to suit the demanding site. No one from Altavian had been to the site in person, but the photos and digital terrain models showed the mesa dwarfing everything in the surrounding area. The job was to have drones collect the data for an accurate topographical map, but it was up to us to ensure the survey proceeded smoothly.
We arrived at Ryan Camp around mid-afternoon. The historic mining camp is tucked into a massive sloping wall adjacent to another equally massive plateau called the Black Mesa. We slowly worked our way around the curving road, following the path of least resistance through the low lands up to the camp site. We photographed everything we could from the ground trying to thoroughly document the site before flying.
The plan was to make a set of notes about both what we identified correctly as well as what we identified incorrectly. As we were documenting the site, our first unexpected hang-up arose: we didn’t have any cellphone reception. This meant, as the team in the field, the remote location inadvertently cut us off from communicating with our offices back in Florida. Luckily, the remoteness of the site also worked to our favor allowing us to quickly find our job contact, Scott Smith, Superintendent, Ryan Operations DVC. Smith had satellite phones which could reach our offices if needed. We finished the first day discussing the area with the Smith. We wanted to glean any extra information about what we could expect and iron out any unknowns.
When we returned on-site the next day, we had a firm mental image of the operation area. Preparation and research created a clear vision of the mission parameters before we launched the drones on their surveying mission. We drove to the top of the plateau with our gear to identify what would be the best suitable landing and recovery site available. Generally, you expect drones to fly at altitudes above you, but launching from the top of the plateau meant our Nova F7200 would fly below us. This was a truly unique scenario.
Upon arriving at the top of the plateau we encountered our next hang-up: the surface of the plateau was rock hard with larger rock formations around the area. The Nova’s construction lends itself well to landing in some of the roughest areas around, including gravel and small rocks. However, some of these rocks were big enough to stop a car from passing. It took us an hour to clear away the largest rocks to form a safe landing zone.
We knew the sturdy, re-enforced construction of the Nova’s body would survive the difficult terrain in ways that a foam plane could not. However, the weight of the body and specialized wing also lent themselves handsomely to overcoming what we knew would be the final challenge of the project: surviving the shearing mountain winds.
The Survey Mission
After a smooth hand-launch off the side of the plateau, we brought the drone up to altitude to begin the survey. The Nova pushed through the wind toward the takeoff loiter. Once it was at altitude, the drone began its first few flight line passes over the crest of the plateau. We watched the drone carefully, monitoring from the ground control station.
A big challenge surveying a site with so much altitude change is maintaining a consistent ground sample distance (GSD). Thus, as the Nova completed each flight line, it continued to slowly descend down the plateau to the next line. Along each flight line, the drone would follow the terrain and keep a consistent, safe distance. We sat silently on the plateau edge watching the drone survey in the calm air below us. From the first flight line to the last, the drone dropped 200 meters in altitude down the side of the mesa.
After completing the survey job, we rallied the aircraft back to altitude and began our landing approach. We took a few low approaches to get a feel for the winds before landing. The Nova set down with a hefty thud on the rocks next to us. Happy the data was safely back on the ground, we began packing up to head back to Florida.
Generating the Topographical Map
We sent the data to the home office in Florida and it was in processing before we arrived. This was the first time Altavian processed a steep rock face and mesa. The completed 3D point cloud and textured mesh let us closely inspect all the rocks and edges. Google Earth missed these features as it was comparatively low-resolution. We processed this data with Pix4D and created the accurate, detailed topographical map for the client.
Flying Ryan Camp shows the utility that the Nova F7200 and drones in general offer to diverse challenges. The bottom line is that drones provide a cheaper way to gather accurate data. In this case, they facilitated generating a topographical map, without flying manned missions or relying on Google Earth.