Drones/RPAS/UAS: Surveying’s new fact or another passing fad?
There are many names for them, and just as many opinions about their suitability as a survey tool. Based on inputs from industry experts, this article seeks to ascertain whether RPAS will redefine the act of surveying as we know it, or become just another hyped up ‘tool’ to add to the box.
Many claim that the accessibility, lower cost and ease of use of drones, or RPAS as we’ll call them here, is progressing to the point that older surveying methods will become redundant. The counter argument lists a bevy of reasons—safety, privacy, reliability, batteries, sensors, training, georeferencing—why for most situations unmanned systems’ novelty is getting in the way of best practice.
If you listened to the hype
If you paid too much attention to market reports and mainstream media’s coverage of RPAS, you would think they could solve just about any problem. They have promised to replace our conventional means to film you snowboarding (*cough*Lily drone); to deliver your pizza faster; and to spot sharks before you hop in the ocean. Why not, then, also replace surveyors and their slow and expensive methods to deliver surveys faster?
You can certainly do some impressive things with RPAS that have captured the imaginations of would-be aerial surveyors. Every week there seems to be another RPAS that can perform another ‘first’ or offer something ‘unprecedented’. Among them: real-time data viewing and analysis; RPAS with LiDAR; RPAS with Simultaneous Localisation and Mapping (SLAM); hyperspectral sensors; and autonomous systems that operate beyond visual line of site (BVLOS).
Once you’ve landed your RPAS there’s also a plethora of software packages to ensure you make the most of your data. These are very exciting prospects and with them RPAS can in many cases perform better than other surveying methodologies. Where we find disagreement, however, is just how often RPAS does and will perform better.
The ‘hype’ of commercial UAVS has not reached its peak. Data based on Gartner’s Hype Cycle, 2016.
Anton van Wyk, director at Spatial Technologies Pty Ltd believes that the RPAS industry in Australia and the world is following the Gartner Hype Cycle (pictured above).
“As you can see, the ‘hype’ of commercial UAVs is not at its peak yet,” Van Wyk said. “Every man and his dog with a UAV or hobbyist with some drone flying experience are trying to get into this market.”
However, what Van Wyk finds most disturbing is “how many of them claim expertise in surveying work.”
“What we have found is that they do the flying on these projects, but because they do not know what they do not know, deliver incorrect or bad quality data. This has caused us to go back to customers and highlight the shortcomings and try and convince them that UAVs are the way to go, if done correctly.”
Spatial Technologies Pty Ltd use RPAS and GNSS in conjunction.
Van Wyk attributes Spatial Technologies Pty Ltd’s ability to have RPAS surveys “done correctly” to the company’s foundation in surveying, GIS and engineering.
“We have been very successful in doing feature surveys using RPAS and exceeded the expectations of the customers,” he said. “This boils down to understanding accuracy and surveying in general.” However, Van Wyk has also come across many instances where he would strongly suggest not to use RPAS. In many cases, people’s desire to solve their problems with RPAS gets in the way of best practice. In one instance, Van Wyk received the following request: “I want to monitor a building roof with a drone.” After asking a few questions, Van Wyk decided that rather than RPAS, a 20 metre pole attached to the roof with a GoPro was the cheapest and best solution.
Aerial Acquisitions is a Sydney-based aerial surveying firm operating both manned and unmanned aerial surveys. Director Max Eichorn also believes the advantages of RPAS as a survey instrument have been over-exaggerated.
“The UAV industry always states the exaggerated cost of manned survey methods and claim they are the future,” Eichorn said. “The manned survey sector has evolved, with the development of extra-large format cameras, RADAR and LiDAR, but has not gained the public’s attention like UAVs.”
“After discussions with some UAV operators,” he said. “I question their claims of economy and even safety.”
When you should NOT use them
You hear a lot about the endless possibilities of RPAS, but considerably less about their shortcomings. When, then, should we not use them? When looking to cover large areas, established remote sensing methods, including satellites and manned aircraft, have distinct economic benefits that are hard to beat.
Flying RPAS over hundreds of hectares will quickly raise many issues such as battery life, the threat of eagles, propagation of errors and restrictive legislation. Dr Craig Roberts, a lecturer in surveying from UNSW’s School of Civil and Environmental Engineering, says that RPAS “are great for small scale mapping.”
“If it starts getting too large,” he said, “traditional photogrammetry with a manned aircraft becomes important.”
Building interiors and exteriors acquired using Hovermap’s SLAM-based LiDAR mapping UAV platform.
At the other end of the spectrum, for small jobs, many ground-based methods are just as effective and devoid of the complications that RPAS bring. In urban areas or close to airports, it is very difficult—and indeed dangerous—to operate RPAS without special arrangements. Often a total station and a level is still the most accurate and economical means. These days there is a long list of methods available in this domain that might also perform better: laser scanning, photo-reality modelling, simultaneous localisation and mapping (SLAM), or simply a tape measure.
It’s also not necessarily about the size of a job, but what exactly you wish to achieve with the data collected. Dr Roberts said that while it is not difficult to achieve better than 30mm in position and 50mm in height with RPAS, going beyond that requires special expertise.
“It is possible to improve this accuracy but this is where the skill of surveyor is required,” he noted. “Understanding control surveying, error propagation and uncertainty, and suitable geometry on the ground and photogrammetrically is crucial to squeeze extra performance out of commercial off-the-shelf UAS.”
Importantly, Dr Roberts also highlighted that RPAS are generally inappropriate for cadastral surveys.
“UAS cannot replace cadastral surveying now as it is raster based and cadastral is vector based and relies on monumentation not coordinates,” he explained. “It would take a change in legislation to enable this.”
Senior Director for Reality Modelling at Bentley Systems, John Taylor believes that it is what you wish to achieve that should define the tools used.
“The level of survey accuracy is always key to these debates,” he said. “To say that UAV-based surveys do not deliver value discounts the relative accessibility that such systems offer, coupled with solutions that enable non-surveyor practitioners to process data and deliver suitable results.”
“There is also potential to improve the accuracy of the derived data through increasing use of PPK and RTK GPS positioning and for many surveys the level of accuracy may be fit for purpose, but in the short to medium term, there is a strong case to be made that these systems will not make other survey methods fully redundant.”
“Where high accuracy is required, then the traditional techniques will continue to deliver the results,” Taylor said.
When you CAN use them
Despite all of this, it is hard to disagree that RPAS do have their place in surveying. Among other benefits, they are very good for covering small areas for a very reasonable price; fly at very specific times of day or with very short notice; and can carry sensors to otherwise inaccessible sites, such as roofs, cavities or cliffs.
Australian UAV (AUAV) is one company pushing the boundaries of this technology for many types of surveys. Describing themselves as the nation’s “leading drone survey provider” they have flown over 3,000 RPAS flights for more than 200 clients in the past four years. AUAV’s director of operations in New South Wales, Andrew Chapman, says that “Anyone who views drone aerial data as a fad is likely to already be missing out on a lot of work, as companies which do offer this capability will be undertaking work at a much more competitive rate while delivering higher quality deliverables.”
Chapman says that like any tool, “drones can be applied appropriately with great results, or inappropriately.”
“Although it doesn’t make sense to be using them for cadastral survey or other small sites, for anything over about ten hectares and an accuracy requirement of five centimetres or less, they start to show significant efficiency gains,” he said.
Chapman has also recognised a sort of sweet spot for RPAS surveying: “One key application is medium size areas, 30 to 300 hectares, where we can avoid a few days of physically difficult, boring or potentially dangerous field work for a surveyor.”
However, AUAV is also covering sites of up to 5,000 hectares—jobs which Chapman finds “are just not feasible with traditional techniques, but are quite achievable with the right drone equipment and experience on hand.”
A digital elevation model of a quarry created by Australian UAV. Source: auav.com.au
AUAV services dozens of surveying firms that don’t want to invest in or take the risk of purchasing RPAS and the training required. Often these services run alongside traditional survey methods such as aerial LIDAR, terrestrial LIDAR, traditional survey and manned aerial photogrammetry.
“The best balance, as is often the case, is a mix of methodologies: drones for large areas when vegetation cover is not a restriction, manned aerial survey for very large areas (20,000 hectares and up) if the accuracy can be lower, and traditional methods otherwise,” he said. “The drones can handle the data gathering, leaving the surveyor to concentrate on the higher-value work of making the assessments and drafting drawings from that data.”
Francois Gervaix is the surveying product manager at drone manufacturer and software provider senseFly. Like Chapman, Gervaix sees that the `challenges’ presented by some jobs—backed by the prospect of efficiency gains—are opening up survey work to RPAS operators.
“It’s not at all unusual for customers to tell us that, with drones, they are doing the jobs that other surveyors often don’t want to, or can’t, do,” Gervaix said.
“Many sites are challenging, due to access issues, regulatory issues, or often due to health and safety concerns,” he said. “UAV technology enables professionals to tackle projects on such sites quickly and effectively.”
Another RPAS manufacturer, DJI, sees potential for surveying applications to benefit from multi-modal approaches involving RPAS. “It would be misleading to state that drones are the appropriate solution for every project, industry, and client,” said Jan Gasparic, Head of Enterprise Marketing at DJI. “Rather, we see drones supporting a photogrammetry workflow working in conjunction with high accuracy terrestrial laser scanners rather than displacing traditional methodologies.”
“While quadcopters themselves are becoming very simple to use, deploying them to produce accurate data and interpreting it correctly will require seasoned hands.”