Unmanned aerial systems (UAS) are having a significant impact on many industries including surveying, mapping and engineering. As the UAS market evolves, many issues arise around the evolution of hardware and sensor platforms, data processing software, O&M best practices, and regulatory frameworks. Our clients are regularly posing questions to us about what is happening with this technology, what is really feasible, and where it’s all going. To help address those questions our UAS team compiled this Q&A.
What resolutions and accuracies can be obtained from a UAS?
Many factors go into the determination of resolution and accuracy of UAS data. Typically, a ground sample distance (GSD) of 1cm, sometimes called “resolution,” is achievable with a variety of different sensors flying at reasonably low altitudes (e.g. 50m) on a rotary wing platform. With a fixed-wing UAS, 2-3 cm GSD is feasible. Many UAS manufacturers promote their ability to achieve very tight horizontal and vertical accuracies without the use of ground control points (GCPs) due to their high image redundancy. You can anticipate obtaining horizontal and vertical accuracies of 3cm and 6cm, respectively. With ground control points, and possibly the inclusion of a ground station such as with Sensefly’s eBee RTK, we can achieve vertical accuracies of 3cm or better.
Construction Site Photomosaic – Rotary Wing UAS @ 60 meters AGL
What are the most important things to keep in mind about UAS?
Two things: 1) collect usable data, and 2) be safe. It’s easy to collect a lot of data from a UAS. Our focus is to collect data in a manner that allows it to be integrated with other datasets to deliver fast and accurate 3D geospatial data. Also, safety is paramount. We follow rigorous procedures and safety protocols throughout the flight planning, field acquisition, and demobilization process, including formalized pre- and post-flight checklists, flying within visual line of sight, and using at least one visual observer to support the flight.
Do I need a pilot’s license to fly a UAS?
Many countries already have UAS commercial use regulations in place. Those regulations address pilot certification. Given that the FAA’s recent 333 exemptions have stated that the UAS pilot in command have at least a private pilot certificate and a third class medical certificate, we believe that the FAA will require UAS pilots to have some aspect of pilot certification. We have a licensed pilot on staff and we consider that an important aspect of our program. However, we have also found that a non-licensed UAS pilot doesn’t need a license to be safe and effective as long as they have a strong understanding of flight principles, airspace, and air traffic control, as well as ample time on a flight simulator and rigorous use of formalized operations and maintenance manuals. Either way, significant effort is required to pilot a UAS.
Flight Test of UAS at a Farm in Rural Wisconsin
Sensors on a UAS can collect tons of data quickly. How do you handle it all?
This issue should sound familiar as the industry has gone through this sort of thing occasionally such as with the advent of digital imagery in the '80s and the growth in popularity of lidar in the last 15 years. It’s common to acquire hundreds of gigabytes of data when flying a project site when you factor in still shots (nadir and oblique), raw video, and video embedded with telemetry. Combine this with derivative products, and data management becomes a major issue. A few rules we follow include:
1. Perform proper data management procedures, including backups and archives.
2. Ensure field and office equipment has the appropriate graphics capabilities and data storage available to house the data, even if only temporarily.
3. Streamline processing procedures to eliminate unnecessary derivative data products.
4. Consider the use of cloud-based storage options. Numerous vendors offer services.
What’s up with the FAA and UAS regulations?
The surveying and mapping industry is anxiously awaiting the long delayed proposed rulemaking from the FAA on commercial use of small UAS. Continental Mapping will actively engage in review and comment on that when it’s released. Also, the FAA is reviewing numerous exemption requests based on Section 333 of the FAA Modernization and Reform Act of 2012, as well as many Certificate of Waiver or Authorization (COA) requests. Each of these issues gets us closer to commercial use.
Are there any gotchas with UAS for surveying and mapping?
There are several areas to consider:
1. Safety: Autonomous flight of a UAS may seem easy, until something goes wrong. Lost communications, or sudden site changes such as oncoming aircraft or weather. Rigorous procedures should be in place and the acquisition team should be well trained on their execution.
2. Obscured areas are still obscured: Most UAS demos on the market today showcase open areas such as mines or gravel pits. That’s because it’s a whole lot easier to derive a bare earth model from UAS captured imagery or lidar when the location is bare earth. To get a bare earth surface in obscured areas due to vegetation, shadows, or buildings, manual processing is still required to map those areas
3. A skilled UAS pilot and support team is needed: Flying a UAS is not the same as using other survey equipment in the field. A UAS pilot must be well trained in the use of the UAS, ground station, radios, and other system equipment; as well as the mechanics of flight, airspace and air traffic control issues, operations procedures, and all safety procedures. Flight checklists and flight logs must be maintained, and the pilot must keep their flight skills fresh through simulator and field flight time.
4. Data Review: Ensure data is reviewed before the acquisition team departs the site. A brief but thorough review of data prior to departing to the project site will ensure that what was captured meets the specifications and intent of the job at hand. Considerations should be given to voids between parallel flight lines and holidays for planned waypoints.
5. Base station RTK missions require continuous and unobstructed communications between the base and the airborne sensor. Site characteristics may present unforeseen obstructions between the UAS and the pre-planned base location.
What is state of the art for UAS?
UAS is a very dynamic component of the surveying and mapping industry. There are several areas we would characterize as the state of the art:
1. Aerial lidar: Survey grade accuracy lidar sensors are typically too big to hang on a small UAS platform. Riegl recently released their RiCOPTER UAS, which is the first commercially available small UAS to carry a survey grade lidar sensor. Currently, mapping grade lidar sensors can be carried by a variety small UAS. Heavy lift UASes are gaining in popularity, and can carry lidar sensors, and smaller, lighter weight sensors are under development to support this need.
2. Full Motion Video (FMV) & GIS integration: Within the intelligence community, video with MISB-compliant metadata has been integrated to GIS base mapping for several years now. The commercialization of this technology is just beginning through tools such as Esri’s FMV add-on for ArcGIS. Georeferencing video to geospatial repositories significantly increases the value of video captured from UAS.
3. Augmented Reality: Augmented reality is already available in social media applications such as Wikitude and HERE City Lens. Riegl’s RiALTY integrates point clouds with hard copy base maps. UAS will be a data source to present augmented reality within.
4. UAS Swarms: The ability to integrate multiple UASes under the control of a pre-programmed flight plan extends the range of data collection to multiple sensor types and sensor locations for coordinated collection efforts. Sense and avoid technology will enable this approach in the future.
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