A Day in the Life of a Drone Surveyor
Surveyors often want to know how UAVs can improve their efficiency and are curious about what working with a UAV is really like. To help answer that question, Waypoint interviewed several senseFly drone operators from different fields and countries.
The drone surveyors we spoke with are all experts in their field, boasting several years and thousands of flight hours of collective drone experience. Each operator recounted what a typical day of drone surveying entailed, what they did to prepare and what challenges they faced.
The drone surveyors Waypoint spoke with include:
- Rachel Kohlman – Project Manager at Meridian Surveys (Alta) Ltd. (Canada)
- Thomas Follet – Founder and CEO at Cartodrone (France)
- Sébastien Burgener – Geometry Engineer at GEOSAT (Switzerland)
- Kevin MacNabb Owner and President at MWH GEO-Surveys (USA)
Getting to the ‘office’
While working with drones is fun, there’s a lot of preparation involved to ensure a successful flight. For our experts, that means arriving early, coming prepared and being ready to tackle whatever challenges a project might throw their way.
MacNabb: Our small crew assembles in the hotel restaurant at 6:00 a.m. All our gear will have been prepared the evening before. Because the eBee flights always take place at remote mining sites, we make sure and have a dozen or more charged batteries, and that the flight maps and the SRTM elevation model of the area of interest have been downloaded from the invariably slow hotel internet.
Kholman: Our day typically starts at 7:00 or 7:30 a.m. in the office but a UAV day will start as early as needed to get the job done. We had one where we headed out at 4:30 a.m. so that we could get the job done and move on to other jobs we had lined up that day.
Burgener: We typically start around 7:30 a.m.
Our day typically starts at 7:00 or 7:30 a.m. in the office but a UAV day will start as early as needed to get the job done
Follet: My missions are generally a few hours away by car from the office, so I often start at 5:00 or 6:00 a.m.
The project(s) await
Some of the operators interviewed work as contractors or consultants for clients across industries. Others work for engineering firms and small government agencies. Thankfully, fixed-wing drones such as the eBee and eBee Plus suit a wide range of functions and industries, so that versatility is reflected in the scope and size of the projects the drone operators can work on in a single day.
MacNabb: Our projects often span multiple days and typically range from 25 to 100 square kilometers in size. Running the maximum number of flights per day is always our goal. For us, ample batteries, SD cards and continuous power for the PC are essential. A successful day is 10 or more flights consisting of 10 square kilometers. The eBee is cycled through its flights with only a battery swap and an uploaded flight plan.
Kholman: We wouldn’t typically fly more than 254 ha in a single day. That’s because most of our projects don’t exceed this size.
Follet: I would say 50 percent of the projects I survey can be done in a single day, not including the image processing. Forty percent of the remaining jobs would last two to three days, and I have had a few missions lasting one week or more.
A successful day is 10 or more flights consisting of 10 square kilometers.
Burgener: My day usually consists of a drone flight for digital terrain mapping (DTM) in the morning and quarry surveying in the afternoon.
Skilled drone operators know that solid planning is crucial to a successful flight. Often, that means knowing the exact region that needs to be mapped, identifying suitable takeoff and landing points and, perhaps most crucially, making sure the necessary permits and permissions are obtained beforehand.
Kholman: With a larger job, our flight preplanning in eMotion is quite extensive. That’s because we always try to maximize flight coverage without giving up much time. With smaller jobs, flights are usually planned out on the job site.
Burgener: First, we look for flying obstacles and a good place to take off and land. Then we define the GSD (Ground Sampling Distance) we need, analyze the terrain to figure out our image overlap, determine which direction to fly and assess whether or not we can make perpendicular flight lines, as this will have a lot of effect on the overlap.
Follet: I usually prepare the mission a few days before and pack everything I need to be on site just after dawn. Time spent on the field is precious and I don’t want to waste it. I mainly use two different scenarios, one achieving 5 cm accuracy, and using perpendicular flight lines, the second one achieving 10 cm accuracy. I’m using a quotation tool I developed, which is available online. With it, clients draw the area they need to survey on a base map, select the desired accuracy and I gather directly this area in an eMotion-compatible flight plan format. I have to adjust the orientation of the flight lines, and check a few parameters, but it’s a really straightforward process.
The UAV operators interviewed know that successful flight planning also means considering weather conditions and, in some cases, making sure all the not-so-straightforward local laws are obeyed.
Kholman: With any request that comes in we make sure to look at the airspace, whether we can fly within our regulations and we look to see if we need to contact the regulating authorities like Transport Canada and any local airports. We also look at the weather because we need to make sure we have all the equipment necessary, such as batteries and other backup equipment.
Burgener: Living in a mountainous region, I almost always have to check the satellite visibility to get flight timetables. I also check whether the place I want to fly requires permission. Sometimes I can get authorization via a phone call. Other times, I can get it through the mail, where one week in advance is generally enough time for that. When it comes to airport permissions, I’ll need to request permission at least three weeks in advance, if not more.
I usually prepare the mission a few days before and pack everything I need to be on site just after dawn. Time spent on the field is precious and I don’t want to waste it.
Follet: I operate in France and the French regulation is as French as it could possibly be – complex and time-consuming! I often have to write protocols that need to be approved by several authorities, fill out a form for each flight and so on. The benefit, though, is that as long as I declare everything properly, I can fly most places (except over urban areas). With some authorities, I can expect at least a 15-day delay to get a clearance.
MacNabb: At extremely remote sites in Central America or Africa, where we often work, the local air traffic of concern are usually circling hawks or vultures!
On-site: playing it safe
With the bulk of the pre-planning out of the way, it’s time to step on-site, where pre-flight safety checks are a must.
Follet: Security first! I would never launch a flight without checking whether the area is free from obstacles and unauthorized people. This step is usually done simultaneously with GCP positioning. And, of course, I call the nearby control tower if necessary.
At extremely remote sites in Central America or Africa, where we often work, the local air traffic of concern are usually circling hawks or vultures!
MacNabb: We arrive at the site and first locate a suitable landing area. Then we try to hire a responsible local to perform crowd control. We could be in the most remote African site on earth, but by the end of the day, we will have a crowd of 50 or more watching the show!
Kholman: We have internal forms and safety checks in place that need to happen at the start of every job, and some inspections that need to happen before and after each flight.
Burgener: Prior to flight, I check if the take-off and landing zone is ok. Then I remove everything I need from the case and mount the drone 10-15 meters away from the box. I do this so the mission’s start waypoint won’t be on the box. That’s because the eBee is so accurate it can land on the box! Then I check the wind, load up the route in eMotion and I’m ready.
Follet: Preparing the eBee is really simple. I just usually try to turn the camera on and off to check that it works properly.
Kholman: We typically set up with our laptop and load eMotion. We take out all the pieces of the drone and inspect them to make sure they are in good working order. We put the drone together, place it in an open safe area for take-off and landing and put the battery in. We then let it orient itself and go through our drone safety flight checklist and review all safety procedures in case of a fly away or crash. Once that is all done, we pick up the drone to ensure everything is showing up in eMotion properly and that it will take a photo with no issues.
To GCP or not to GCP?
When it comes to setup, specifically regarding ground control points (GCPs), not all the drone surveyors Waypoint interviewed use them. But those that do have their own methodology in place to ensure their work is as accurate as possible.
MacNabb: We set and survey our own GCP sites. GCPs are laid out in advance either by the eBee crew or by our geophysical surveyors.
Kholman: We set GCPs for some jobs and not for others. It really depends on what we need the data for. We’ll usually use whatever coordinate system is in place already or needed. If using GCPs, we plan out their placement, checkpoints and place them prior to flight.
Burgener: I try to use existing elements such as street marking, but if needed I set GCPs. We mostly use CH1903+/NF02… if there is enough street marking, I mostly choose and measure them after a flight.
We set GCPs for some jobs and not for others. It really depends on what we need the data for.
Follet: I always set ground control points, a minimum of 10 per project. I use the coordinate system specified by my customer. I use white 30 cm x 30 cm targets, which are set prior to flight and removed afterward.
Time to fly
At this point, it’s usually mid-morning and the afternoon is on the horizon. But before the surveyors launch, we were curious as to which senseFly drones and cameras they trust to get the job done.
MacNabb: We use the eBee. We have a thermal camera, an S110 RGB and a senseFly S.O.D.A. RGB.
Kholman: We use the base eBee model. We mostly use the RGB camera, although we do have other sensors.
Burgener: A standard eBee, which we’ve had for about three years now, and an S110.
Follet: I use an early version of the eBee (from 2012) but it’s still in really good shape! I just bought a brand new senseFly S.O.D.A. camera and I’m glad I did!
With the drone up in the air, it’s time to monitor the flight. While some of the operators interviewed prefer to operate alone, others work with an observer – a choice often driven by local UAV regulations.
Follet: I work alone, and monitoring is quite an easy task. Most of the flights are made from outside my immediate sight, so I spend most of the time with my eyes on the screen of my laptop.
Kholman: For our flights, we operate with at least two people, which is required by the regulations here in Canada. But I also think that’s a good thing. It would be near impossible to keep an eye on our equipment, make sure it’s flying properly, watch for other aircraft and make sure that no one wanders into our take-off and landing area.
I use an early version of the eBee (from 2012) but it’s still in really good shape! I just bought a brand new senseFly S.O.D.A. camera and I’m glad I did!
It’s not always smooth flying, though. There is always the potential for flight hazards, such as birds and strong winds. Skilled and successful UAV operators must learn to expect the unexpected.
Kholman: We’ve had a few times when a hazard has raised its head. After a day of flying in the wind, we instituted a top airspeed for company flights, and that’s with wind gusts of up to 35 km/hr. Although it’s recommended to fly at a lower wind speed, sometimes it’s unavoidable. We’ve had at least one job where we had a hole in the data due to an eagle “protecting” its nest. Every time we flew anywhere near its nest, we would have to take evasive maneuvers because the bird would appear out of nowhere. After a while, we could see it circling at very high altitude, and whenever we came near, it would just dive for the eBee! No matter how many times we tried we couldn’t get enough photos for data in this spot.
MacNabb: We haven’t been able to discuss with the vultures a suitable code of conduct yet. Our eBee has had several close calls and one direct strike by aggressive or amorous birds.
Burgener: Some Swiss birds have shown interest but have never attacked. The wind can be calm and become strong very quickly in our region, too. It happened once where we had a strong front wind that prevented the drone from returning. But even without any battery charge left, the drone made a soft landing in a field. Actually, my biggest fear is helicopters. There are a lot of them flying around in the mountains, and they come quick and fly low.
We haven’t been able to discuss with the vultures a suitable code of conduct yet. Our eBee has had several close calls and one direct strike by aggressive or amorous birds.
Follet: The birds I usually meet in France are quite well-disciplined! Weird winds are tricky, though. I would say winds are my worst fear when working in mountainous regions.
Sticking the landing
What goes up, must come down – and our drone operators want to make sure that what comes down does so reliably and safely.
Follet: I prevent landing on gravel as often as possible because it tends to scratch the body of the eBee. Small rocks in gravely areas are my worst enemy. I always check the landing area to prevent damaging my drone.
Burgener: The canton of Valais, here in Switzerland, is rocky. There aren’t many flat sites to land, and there are lots of rocks, high trees and cliffs. Of course, even if there is only one rock in a big landing field, your drone will always land on it… Fortunately, the eBee is a tough drone and easily repairable.
Kholman: My preference is to land on grass but that’s not always possible. One issue we run into here in Canada is canola stubble. It’s like trying to land on a field of very tough plastic straws. It does a bit of damage every time, so I will sometimes try to cradle catch the eBee in these situations, although it doesn’t always work! One time in training we did have a user launch directly into the ground. Of course, the eBee was fine – they do a controlled crash landing after every flight – but the user has had a hard time living it down!
Fortunately, the eBee is a tough drone and easily repairable.
Once the drone comes back down to earth, it’s not long before it’s up in the air again. But before it can take flight once more, some quick checks often take place.
MacNabb: We check that the eBee has a propeller and wings! Then back into the air it goes. Often the eBee is on the ground for less than two minutes before it is sent off on the next flight.
Follet: I always do two things: after landing, I launch a rapid check with Pix4D to test my imagery’s overlap and general quality and, while it’s running, I glance at the pictures to look for any anomalies.
Kholman: After the flight, we typically look at the images on the SD card to ensure there have been no issues.
Burgener: I don’t check. I trust my experience and always try to take more data than needed.
Leaving the site
Once all the flights are completed, it’s time to pack up and leave the project site.
MacNabb: With a dozen dead batteries and a depleted PC power supply, we head back to the motel. Bad roads and an hour or two to return are the norm.
Kholman: Typically, we try to be back at the office by 5:00 p.m., but that depends on the job.
Burgener: I can’t give you an exact leaving time, but we tend to fly when the sun is higher, which helps decrease shadow coverage.
Follet: I usually leave after dusk. I tend to stop flying in the middle of the afternoon, and I would spend the remaining daylight time collecting the ground control targets.
Analyzing the day’s work
Leaving the site doesn’t mean the end of the working day for a drone operator. With gear in tow, it’s now time to process the imagery.
MacNabb: Our first step is to copy SD cards and all flight logs. The GNSS survey must also be downloaded or processed to compute the GCP locations. I try to process two to three flights overnight. With 10 or more flights flown per day, our processing quickly lags behind the acquisition, though.
Kholman: Typically, we’d start processing that night, once we got back to the office. This way we should have some results by morning.
Burgener: I start processing at night so that I’m able to work on the results the next day. Using Pix4D, I always do a quick processing; it’s easier to snap my GCPs in the Raycloud editor.
Follet: When I’m back in the office, the processing is already running!
With their data collected, we asked each drone operator what computing rig they typically use for photogrammetric image processing. One operator responded that they use a field laptop, another utilizes both a laptop and a dedicated PC, while the other two explained that they use a dedicated PC in conjunction with a discrete graphics processing unit (GPU) for faster computational speeds.
Of course, beefy computer hardware isn’t the only thing a drone surveyor needs to get the job done; they also require the right photogrammetry software to transform the drone’s photos into orthomosaics, digital point clouds and digital surface models.
We use Pix4D for processing. This is what we started out with and it has worked great for us. It’s easy to use and we don’t have any issues…
MacNabb: We use Pix4D, which takes roughly three processing days per one flying day for our projects.
Follet: I use Pix4D for processing, which at the time was included with the drone. It’s one of the best processing software programs available.
Kholman: We use Pix4D for processing. This is what we started out with and it has worked great for us. It’s easy to use and we don’t have any issues… I would say hands-on time might be six hours and it may take the computer two nights and a day. So, typically, we would have usable data within a day or two.
From data to deliverables
Once the drone’s photos have been processed, it’s ready to produce the formal deliverables. These vary depending on the client and project.
MacNabb: We typically supply a digital elevation model and an orthophoto or thermal image map.
Burgener: We deal in DTMs and DSMs, which can be meshes or contour lines, or even orthomosaics.
Follet: I always deliver both an orthomosaic and point cloud data—not in the original format though—even if only one is required.
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