The Mavic Air can capture video in 4K at 30fps and has a flight time of 21 minutes
JAMES TEMPERTON 23.01.2018 03:30 PM
DJI has announced the Mavic Air, a new mid-range drone that sits between the diminutive Spark and the high-end Mavic Pro.
The Air is the company’s most practical yet portable drone to date: weighing in at 430g, the drone’s folding arms sit flush against its body to create a chunky, smartphone-sized block that can easily be carried around.
Unlike some smaller drones, the Air is kitted out with the necessary tech to capture crisp, steady video. The three-axis mechanical gimbal is suspended from dampeners and the Mavic Air captures still images at 12-megapixels and 4K video at 30fps. If you’re after slow-mo shots, these can be captured in 1080p at 120fps. As an added bonus, DJI’s panorama system can stitch together 25 photos to create a 32-megapixel image in around a minute.
The Mavic Air comes with 8GB of onboard storage and an microSD card slot. There’s also USB-C for speedy exporting of captured footage. The drone has a maximum flight time of 21 minutes and can fly in winds of up to 22mph and elevations of 5,000 metres.
DJI has also squeezed in seven onboard cameras and infrared sensors, which combine to construct a detailed map of the drone’s surroundings. Forward and backward facing cameras can detect obstacles from 20 metres away and help the Mavic Air automatically avoid crashes.
The 1080p live video feed has a range of 2.5 miles for first-person view control and in Sport mode the Mavic Air can reach speeds up to 42mph. Hand gesture controls over a distance of six metres are also supported – commands include push, pull, land and capture.
The price and specs fill a gap in DJI’s drone line-up, with the Mavic Pro Platinum capable of flying for 30 minutes and the Spark not able to film in 4K.
It’s available in three colours – black, white and red – and costs £769 complete with drone, battery, controller, carrying case and two pairs of propeller guards and four pairs of propellers. The Mavic Air is available to pre-order now and orders start shipping on January 28.
After the cathedral of Christchurch, New Zealand, was hit by an earthquake, drones and advanced photogrammetry software supported the rebuilding work.
Surveying a damaged building can be dangerous. Mapping, using drones, reduces risk to staff and costs to the community. This case study of the iconic cathedral of Christchurch, severely hit by an earthquake, demonstrates how drones and advanced photogrammetry software delivered the orthomosaic map, enabling the accurate spatial planning needed to rebuild the cathedral.
In February 2011, New Zealand’s second most populous city was rocked by an earthquake. The iconic Christchurch Cathedral was shattered in the shake, and the clean-up is still ongoing. Christchurch's central city and eastern suburbs were badly affected.
Before the cathedral could be rebuilt and the 'red zone' surrounding it rejuvenated, a full survey was required. Christchurch City Council’s surveyor Jed Clement, licensed cadastral surveyor, stepped up to the task with the help of drones and Pix4Dmapper.
Locals describe Cathedral Square as "the heart of the city" and as being "key to Christchurch". It sits in the centre of Christchurch, both metaphorically and literally. The garden city, with its large urban parks bisected by the sleepy Ōtākaro Avon river, is known for agriculture, for being the gateway to Antarctica and, more recently, for earthquakes.
New Zealand is stretched across a fault line and earthquakes are common, although seldom as severe as the 2011 quake. By August 2012, the area had experienced more than 11,000 aftershocks of magnitude two or higher. Aftershocks were felt up to 300 kilometres away from the epicentre.
Strict building standards no doubt saved many lives. Scientists estimate that the shake that damaged the cathedral would have “totally flattened” most cities around the globe. The timber-framed homes favoured in New Zealand are relatively resistant to earthquakes, and most damage was sustained in poorly-designed buildings, or stone structures like the Christchurch Cathedral.
Prior to the 2011 earthquake, the cathedral had been damaged by earthquakes in 1881, 1888, 1901, 1922 and 2010. However, the greatest damage occurred in 2011. The first shake destroyed the spire and part of the tower, and left the rest of the building severely damaged. Aftershocks collapsed the west wall of the cathedral, and what was left of the tower had to be demolished in 2012.
Rebuilding After the Earthquake
As the city and the nation debated whether the Cathedral should be rebuilt at all, worshippers gathered in a temporary ‘Cardboard Cathedral’ made out of comfortingly earthquake-resistant materials – including cardboard. But now the cathedral is being rebuilt and commercial development in Cathedral Square and the surrounding area encouraged. Access to the area has been limited due to quake damage, and it’s hoped the development will revitalize the area.
To assist with the rebuild, the Christchurch City Council team launched a drone flight to capture ground levels and provide an up-to-date orthomosaic drone map of Cathedral Square to allow for accurate spatial planning.
The Benefits of Drones in Dangerous Situations
Much of Cathedral Square is open, but there were areas of the Square that were impossible to access due to the risks relating to construction as well as the damaged buildings, including the cathedral. Aerial photogrammetry was therefore the best choice for capturing data in these areas.
The drone could fly inside the restricted perimeter fences without risk to the operator. Just as importantly, Pix4D’s algorithms allowed for the optimal capture of imagery to render a high-quality 3D model that the surveyors could use to take precise measurements – all without entering the site.
Mapping an Inaccessible Area with Drones
The flight team met in Cathedral Square at 8am on a Sunday morning. The early start meant fewer people around the square and fewer vehicles on the road. While this caused less disruption to the public, it also had advantages for the team. Moving objects (like cars and people) may appear in the orthomosaic as transparent artefacts. While it is possible to remove these 'ghosts' and improve the appearance of the orthomosaic, the early start allowed the team to avoid capturing them in the first place.
The Christchurch City Council survey team’s drone pilots licence is pending, and they currently operate under New Zealand’s CAA Part 101 operating rules, which also regulate balloons and kites. The aerial mapping flight was approved by the city’s Roading Authority and the cathedral trust.
The team hoped for overcast weather, and got it. “We were concerned about the surface being quite reflective, which would mean losing detail in the final outputs,” says Clement. “But the morning of the flight could not have been better, being overcast and with no wind.” A total of four flights were completed: two oblique and two grid nadir to capture as much information as possible.
“Unfortunately, we had an issue with the connection to the drone on one of the flights,” says Clement. “That meant we were missing one set of oblique images over most of the square, which resulted in missed detail on the cathedral and surrounding buildings.”
Despite this issue, the team was able to reconstruct the 3D drone model in less than 23 hours in Pix4Dmapper aerial photogrammetry software.
Before take-off, eight ground control points (GCPs) were levelled to a 5mm accuracy. A further 12 checkpoints were added during processing, giving the mapping project an average ground sampling distance (GSD) of 1.38cm. “Quality ground surfaces and reporting – plus ease of use – is why we chose Pix4D,” added Clement.
Modelling a Moment in History
The model gave the team the certainty they needed to begin the detailed design phase of the southern portion of the Cathedral Square rebuild. This part of the rebuild is to coincide with the commercial development that is underway on the southern perimeter of the square, and is due to begin opening in late 2019.
Regenerate Christchurch notes that: “Redevelopment will acknowledge the past and the events that have shaped the city, while reflecting the best of the new… This is an opportunity to breathe life back into Cathedral Square and re-establish it as the heart of the city.”
The model of the square and broken cathedral is not only a useful tool, but the aerial photography is a snapshot of a moment in the city’s history.
The original version of this article was published on Pix4D.com. Last updated: 24/06/2020
The Challenges of Drone Use in Facade Mapping
There have been rapid advancements in unmanned aerial systems over recent years, yet there is widespread consensus that we have still only seen a fraction of how unmanned aerial vehicles (UAVs or ‘drones’) could ultimately improve efficiency for geospatial professionals and their customers. To get a glimpse of the future, 'GIM International' spoke to Mark Nicolai, co-founder of industry start-up Aeroscan. Here, he shares his vision of how drones could form the missing link between aerial imaging and terrestrial data capture.
According to independent research by the likes of PwC and Goldman Sachs, the construction industry tops the list in terms of commercial drone use and is by far the fastest growing sector. UAVs are becoming increasingly commonplace on building sites, enabling construction companies to monitor progress with ever-greater accuracy, efficiency and safety. The use of data captured by an unmanned aerial system (UAS) is also on the rise in 3D models for construction planning and design purposes. Drone deployment has reached a sufficient level of maturity that activities such as UAV-based roof inspections have become fairly routine. Now, a Dutch startup called Aeroscan is taking things a step further and exploring the use of drones for facade mapping. “If this can be achieved, it will have major implications – not only for construction and real estate but also for infrastructure, law enforcement, emergency services, local governments and so on. It relates to every business case already using aerial data, plus it will unlock countless new business cases by providing higher-quality data and more detailed information about the local environment,” states Mark Nicolai, one of the two co-founders of Aeroscan.
Founded in mid-2017, Aeroscan is actually the result of three businesses: a leading Dutch construction company, an IT company specialized in the development of cloud software for construction management, and Nicolai’s visual media company which he started in 2008 and which produced promotional videos and photos of building sites for construction companies, including using drones. “Our photos were mainly used for marketing purposes, but technical departments started to ask whether they could use the photos for calculation purposes too,” recalls Nicolai. “So we increasingly moved into drone-based imaging for construction firms and social housing associations. We have the necessary equipment, certificates and a dedicated drone crew to collect data. We also have customers who are already using our software and 3D models to obtain objective data as the basis for reports, calculations, estimates for repair, and so on. But we’ve noticed that large property owners have a need for real-world insights into the condition of their properties, including their facades, so we decided to take a risk and investigate whether UAVs could be used for this.”
Helping to shape EU drone regulations
“Together with two other partners, VMRG and Octo, we received €1.6 million of EU (EFRO) subsidy from the ‘Kansen voor West II’ programme as part of a three-year project called the Facade Service Application (FaSA). The project involves a consortium of dozens of contractors and multinationals from the entire chain of producing, installing and maintaining facades. We needed a drone operating licence for the built environment, so we applied to the Dutch aviation authority (ILT). When the people at ILT heard about the FaSA project, they invited Aeroscan to work within the framework of a Specific Operations-based Risk Assessment (SORA) for drones and to cooperate with them on the JARUS project which is helping to shape the future of EU drone regulations,” he continues. The Joint Authorities for the Rulemaking of Unmanned Systems (JARUS) is a group of experts from the national aviation authorities (NAAs) and regional aviation safety organizations working to recommend a single set of technical, safety and operational requirements for the certification and safe integration of unmanned aircraft systems (UAS) into airspace and at aerodromes. Presently involving 59 countries, as well as the European Aviation Safety Agency (EASA) and EUROCONTROL, the objective of JARUS is to facilitate each authority to write their own requirements. “In the JARUS project the focus is on presenting a real-life scenario and operation-based risk assessment and proving that your business case is safe. So this was a unique opportunity for Aeroscan to work on this conceptual new framework for future EU regulations based on our actual business plan,” explains Nicolai. “After a process of 16 months, we finally gained approval for our developed scenario in late December 2018 and we now have the most complete certificate that’s possible today: we are flying our drones on a kind of ‘temporary exemption’ based on future EU regulations that are still being developed!” he adds. As a result, Aeroscan became the first company in the history of the Dutch UAV industry to receive an official permit for flying drones in urban areas. “We’re gaining valuable knowledge and insights about how to investigate measures and risks in the field, which we share with ILT. By continuing to work with the authorities we hope to help expand the possibilities of flying in urban areas for the industry as a whole.”
Field pilots for housing associations
For its customers in the housing sector, Aeroscan’s long-term aim is to offer UAV city mapping in combination with photogrammetry/data processing, and to combine automatic image and object recognition techniques with UAV data to find flaws in real estate such as cracks in facades or window frames that need repainting. The company ultimately hopes to generate maintenance insights and data visualizations based on the analysis. So far, the main focus is on the operational aspect, i.e. data acquisition. “Since gaining the licence, we have conducted several pilot projects for social housing firms and property companies using existing off-the-shelf technology. In fact, our first pilot – mapping a row of terraced houses in a small Dutch city – was the country’s first ever official flight of a UAV over an urban area to inspect residential properties. As it was our first time in the field, we just wanted to explore the drone’s performance when exposed to environmental factors such as Wi-Fi signals, GPS, jamming, blocking, reflections, turbulence and gusting around buildings, for example.” The drone hardware Aeroscan uses is an Intel Falcon 8+, which Nicolai considers perfectly suited for inspection flights in high-risk urban environments due to its small size, low weight (just 2.5kg) and eight engines giving triple redundancy (i.e. it can still land safely even if two engines fail). In terms of the imaging sensor, the aircraft is fitted with the high-end Sony A7R full-frame camera to capture images in high resolution. As it turned out, there were no interference problems and the drone data was successfully post-processed into accurate and georeferenced nadir maps of the rooftops.
Simulating a multi-camera rig
In subsequent pilots Aeroscan has increasingly explored how to capture images of facades, because that is where the real added value lies for housing associations. “To tackle the challenge of vertical mapping, we took inspiration from the manned aircraft approach. We started to create flight plans to generate relevant datasets based on the workflow in Bentley’s ContextCapture, considering overlap rules, angle shifts between cameras and so on. In our most recent pilot for a social housing association in a densely populated urban area of a major Dutch city, we worked with an acquisition plan to simulate a multi-camera rig you would commonly find on a manned aircraft. So we designed a setup in which the drone passed each point multiple times, with the camera pointing in a different direction and at a different angle each time. Of course there’s only one camera on the drone, so we had to conduct multiple flights, which means it’s not really such an efficient approach right now.”
Overcoming bottlenecks The Aeroscan team are undeterred by this inefficiency and see various ways to improve it. “The off-the-shelf hardware solutions aren’t based on a UAV city mapping scenario because the current legislative situation means there is no demand for them; so far, manned aircraft have been the only aerial option. We really need a multi-camera sensor that is lightweight enough to be carried by a small UAV but offers sufficient calibration to ensure fixed overlaps and georeferencing accuracy. But I don’t see it as being a huge problem to combine and refine certain types of existing hardware,” states Nicolai. “And the next-generation ‘beetle’ drones – which weigh just 10 to 20kg and combine vertical take-off capability with the range of a fixed-wing drone – could get close to matching the efficiency of a manned aircraft, for example. Having said that, their flight range of approximately 100km in an hour raises other issues, such as which safety standards will need to be in place to allow 100km beyond visual line of sight (BVLOS) flight missions on a predefined grid. So maybe UAV deployment in city mapping will remain limited to small-area projects for the time being, but even so it can still be an interesting alternative to the use of manned aircraft or terrestrial mapping.”
Customer response Conducting low-altitude flights in highly populated and congested urban areas raises not only safety issues but also privacy concerns. Nicolai explains that most clients are excited about working with UAV technology because drones are generally considered “cool and interesting”, but on a practical level the housing associations’ tenants are not always immediately keen to have a drone flying over their backyard or balcony. Aeroscan tackles these concerns from two angles: legislation and social acceptance. “On the legal side, we work closely with our housing association customers to ensure their rental agreements with tenants actually give them legal grounds to use drones for conducting inspections, for example. But more important to us at Aeroscan is social perception and ensuring we don’t invade anyone’s privacy, so we’ve developed an automated workflow to anonymize sensitive data such as faces or number plates,” comments Nicolai. “In the pilots, we’ve made it a priority to inform all the households that have been involved, including through panel interviews and information events afterwards to evaluate people’s experiences. We try to involve as many tenants a possible. After all, a drone is just another tool. In reality, it can be less invasive than the current manual inspection method in which inspectors physically visit premises and sometimes need access inside people’s homes and gardens.” It is important to keep local residents informed. Next steps Now that the operational approach has been proven to work in practice, Aeroscan is advancing to the next phase of developing an end-to-end solution: processing. “During the pilot projects, the datasets were modelled in a pipeline created with ContextCapture. We then supplied those models to our clients as raw data. But we are about to launch our own cloud-based platform with enhanced visualization functionalities so that customers can gain access to the deliverables in their preferred data format, such as high-resolution photography, meshes, orthos or whatever,” he continues. “Then the next step will be to develop automated analysis to truly unburden our clients. That’s our aim: to take an industry-specific and customer-specific approach in order to provide the insights that social housing associations need. We’re partnering with OCTO – a specialist in smart asset management and big data analysis – within the FASA project, for example. By the end of this year, we hope to be conducting tailormade drone missions for property companies based on their predefined business cases: the defects or objects they want to count, measure or find automatically within an area. The information our solution provides will enable them to focus on their core business: planning and performing the necessary maintenance of their properties to ultimately make life better for their tenants.” Mapping facades involves multiple flights with the camera pointing in a different direction and at a different angle each time. Although Aeroscan still has some development work to do, the company is clearly on the right track towards developing an industry-specific end-to-end solution that adds real value for its clients in the Dutch social housing sector. If this is a success, there is no reason why it cannot be rolled out internationally and/or used for other smart-city applications. It remains to be seen how quickly the industry will ‘catch up’ in terms of developing the miniaturized hardware that is required to expand the horizons of drone-based city mapping beyond the nadir view. The topic of legislation and flying permits remains a crucial issue, of course, but the Aeroscan team are certainly doing everything they can to ensure the upcoming EU-wide legislation works in practice so that professional users can truly exploit the full potential of drones for city mapping in the near future.
Author: Lynn Radford
Last updated: 14/04/2020