Drone aerial mapping presents new geospatial possibilities

Drone aerial mapping presents new geospatial possibilities

Accurate data collection and precision mapping will always be among the core skills required for surveyors. However, the rapid rise in drone technology is reshaping the geomatics profession in new and exciting ways. Rather than being pure data providers, surveyors are transitioning to become intelligence gatherers and expert information analysts.

By Chris Kirchhoff*

Over the last 10 years, the ability to create accurate 3D representations of the earth’s surface using unmanned aerial vehicles has gone from being a sought-after, but occasionally used, speciality to a standard tool integrated into nearly all work processes. Photogrammetry and lidar data collection and processing capabilities, combined with big data analytics and machine learning, have so improved in efficacy and cost-efficiencies that the concept of a 3D digital twin is the expected norm.

The global unmanned aerial vehicle (UAV) market is forecast to grow from the current US$17 billion (R284 billion) to $40.6 billion (R677 billion) by 2028. There is not a single industry that does not believe that the integration of UAVs and their use in geospatial data collection will play an increasingly important role in optimising work practices.

We can now debate more realistically about the viability of human-free functionality, automation and advanced artificial intelligence (AI). We can envisage a not-too-distant future where drones are in the air constantly, scanning construction sites, inspecting the work and using the data collected to predict and solve problems before they arise. In turn, earthmoving and allied plant operate remotely.

But, of course, it’s not actually humanfree – it’s just our roles that are changing from doing to managing. As I continually chide my children when they fall behind with their schoolwork: “Do you want to work for a robot, or do you want robots working for you?”

This question has the same bearing for the geospatial and land surveying community. We must grow from being the collectors of spatial information to the interpreters, the analysers and the providers of actionable location intelligence. Within this context, the drone is an invaluable tool that takes us on this new journey.

Time for change

We don’t have a spreadsheet department, we don’t have typing pools anymore… so, why do we have a UAV mapping department? Why do we describe ourselves as mapmakers when we should be calling ourselves location-based intelligence analysts, given the massive advances in software and hardware?

To loosely quote Adam Carnow, if we describe ourselves purely as drone pilots and map-makers, then the response will be, “Thanks. When I need a map, I’ll get back to you.”

Reality capture

To further emphasise why this change of mindset from tool operator to data analyst is so important, it’s important to consider the significance of reality capture and location intelligence. (Location intelligence being defined as the capacity to convert the spatial component of business data into business understandings and visions.)

Jürgen Mayer, president: Reality Capture Division of Hexagon Geosystems, suggests, “Rapid changes in technology and computing power are affecting almost every aspect of our lives – from democratisation and information access to communication and how we visualise the world around us. As technology becomes smaller, more affordable, and more automated, 3D reality capture is becoming more accessible to a wide range of applications and everyday users – not just specialists.”

He suggests that the reasons for this include the fact that: - 3D reality capture solutions form the bridge to transform the real world into mirrored digital realities that can be used for all kinds of applications. - 3D reality capture enables you to replicate the physical world and turn it into a virtual

environment, using software to derive valuable and useful information, such as in building construction, where users can monitor the progress of a project and quickly compare as-built to design-intent models, ensuring quality control and highlighting any issues. - 3D reality capture provides a rich documentation data set so that users can always go back to the site in a digital environment and check asbuilt documentation. Sometimes, the site might not be available anymore, as in the case of a crime scene or car collision. Here, 3D reality capture enables investigators to capture the evidence and clear scenes quickly. Furthermore, these digital environments can be used to test scenarios and create simulations for training purposes. - 3D reality capture is a key enabler in digitising business processes across all kinds of industries, putting data to work to boost efficiency and productivity. As

BIM (building information modelling) processes are more widely adopted, they will heavily rely on an up-to-date 3D model that people can work on collaboratively. - 3D reality capture improves workflows and operations. People working on complex projects benefit from one single 3D model that can be visualised to make decisions from remote places, bringing work functions closer together to improve workflows. - 3D reality capture can be integrated with other new technologies, such as virtual and augmented reality.

UAV developments: software and hardware

If I were asked to summarise the advances in UAV aerial mapping techniques, my answer would be that we have reached a point where the future described above is the new normal. This is thanks to crucial software and hardware advances.

The mainstream software available today greatly improves our processing power and analytical capabilities, as the quality and size of data files steadily increase. Cloud developments further improve information sharing over secure networks. Other advances include the use of web-based visualisation tools to analyse and interpret data through machine learning and AI.

VTOL

One of the major drone breakthroughs is vertical take-off and landing (VTOL). The ability of combining the efficiency and safety of vertical take-off, as used by multirotor drones, with the flight efficiencies of fixedwing drones makes a huge difference in terms of aerial data collection.

The major drawbacks of fixed-wing drones are that they either need to be ‘thrown’ into the air or catapulted using a mechanical launch platform. Their ‘belly flop’ landing style also increases the chances of mechanical failure, camera damage, and shortened operating life.

The major drawback to multicopter drones is that flying operations are inherently inefficient. Flight times and resultant mapping areas are therefore considerably reduced.

However, by combining the ability to take off and land in a vertical configuration, and then flip into a horizontal flying mode, the VTOL drone overcomes all the above inefficiencies.

Trilateration improvements

Traditionally, drones have used onboard GPS receivers that utilise the C/A code on the L1 carrier of the GPS signal structure. Based on this, the receiver calculates its position by trilateration – measuring the distances to four more satellites and establishing the unique intersection of the resultant spheres. Due to atmospheric variations, the accuracy is between 7 m and 20 m.

This is sufficient to create a photo mosaic and establish where the photographs were taken. Then, based on mapping techniques and pixel recognition, an orthophoto map is created. If we add ground control points to the processing, we can then mathematically ‘stretch and fit’ the pixels into a real-world representation with an accurate geospatial aspect.

Traditionally, surveys have used GPS receivers capable of monitoring both the L1 and L2 frequency. The errors resulting from satellite perturbations, ionosphere and troposphere modelling can be removed by comparing the wavelength of variations in these two frequencies in the trilateration process. The resultant accuracies are in the order of 20 mm to 30 mm.

The big advance in drone mapping is that the UAV can now carry L1 and L2 frequency receivers. This data can either be used in real-time or post-processing mode to accurately, within 30 mm, calculate the position from which each photograph was taken.

When this is combined with dronemounted inertial measurement instrumentation, we can now solve the problems of calculating the camera position when GPS signals are not available, such as inside buildings or in mines.

Thanks to these advances in technology, the tools of the geospatial trade are transporting us into a new world of realtime data proficiency and analysis that goes way beyond ‘making maps’.

*Chris Kirchhoff is a professional land surveyor (PLS0962) at 5DGEO Professional Land Surveyors. For more information, email chris@5dgeo.co.za.