Photogrammetry and Drones

Words: Christopher Rodermond 
Photos: Vertigo Drones, Natnan Srisuwan

Photogrammetry is everywhere in our lives though few of us likely use that word often.

It’s simple. Photogrammetry is the process by which multiple two-dimensional images are overlapped and mapped together to form an accurate three-dimensional model of the imagery captured. That is, of course, a gross oversimplification of a broad field of science that strongly overlaps with other disciplines, including 3D data acquisition, aerial surveying, computer vision, geoinformatics, remote sensing, and many others. The applications of this technology can and have been widely used, according to Wikipedia, in “topographic mapping, architecture, engineering, manufacturing, quality control, police investigation, cultural heritage (archeology) and geology.” Most recognizably, technology is used to mix live-action with computer-generated imagery in video games and movies. 

With today’s technology and software, there is virtually no limit to the size or scale of a photogrammetry project, anywhere between planetary efforts like the ambitious and incredible Google Earth to a project using an electron microscope called Microscopia.

In our research for this article, we found many scholarly examples of photogrammetry applied in the lab to research practical applications on strength evaluation, damage quantification, and many other general inspection and monitoring applications.

With the adoption of widespread use of drone technology for a variety of commercial and engineering needs, the ability to pair photogrammetry on architectural and masonry design projects is more accessible than ever. And the time it takes to get a rendering can be incredible. We found a case study online where a 327-acre quarry/landfill site was mapped in 32 minutes with a Phantom 4 RTK drone!

If you are the kind of person, who likes to understand and experiment with a particular technology before adopting it, several free and inexpensive photogrammetry programs are available. The folks at All 3D Printing have recently published an article called “2021 Best Photogrammetry Software (Some are Free)” at their website all3dp.com. We wanted to highlight a few programs that run the gamut in price and functionality from this list. 

1. Pix4D - (pix4d.com) - Price is from $160/month when billed yearly at $,1920 or $320/month monthly. Pix4D is an old name in a relatively new industry and has the benefit of integration with many other systems and can work with many different file types. There is a massive community of users on the web, tons of documentation and learning materials available, and even a certification that can be passed after taking a course online. If price is not a concern and you need an industry-standard product that will integrate with just about everything your clients may be using, this is the system for you.

1. DroneDeploy - (dronedeploy.com) is another robust commercial application that supports Dxf, GeoTIFF, las, obj, XYZ file types and is $149/month or $99/month with an annual subscription. They also offer a free trial, and as they note on their website under construction solutions, “Save time, improve communication, and reduce cost by using aerial and ground data to perform surveys, conduct inspections, and document every job site. Bringing full site documentation into one solution, DroneDeploy enables you to capture interior, exterior, ground, and aerial data. Through a digital twin of your job site and in-depth analysis, projects run on time, on budget, and safely.”

1. MicMac - (micmac.ensg.eu) - This is one of several powerful free software applications, and this one supports GeoTIFF, ply, and XML file formats. The French National Geographic Institute developed this software and has a wiki with tons of documentation and support for new or advanced users.

The list of drones that can be used for photogrammetry is equally as robust. The folks at Multicopter Warehouse (multicopterwarehouse.com) in Centennial, Colorado, produced a seminar in June of 2020 that runs down the pros and cons of different hardware options. We found this seminar extremely helpful and recommend watching the video, but we have again highlighted five examples of popular drone options.

1. Mavic 2 Pro (https://www.dji.com/mavic-2) - The Mavic 2 Pro has a 1” CMOS sensor with a 20-megapixel camera.  It has a 4k video output with a max still image size of 5472x3648 pixels. The drone itself weighs 907 grams and unfolded has a dimension of 322 x 242 x 84 mm. The max speed is 72 kph and has a runtime of 31 minutes at a consistent 25kph. The retail price of this unit is approximately $1,599. 

1. Phantom 4 RTK - (https://www.dji.com/phantom-4-rtk) The Phantom 4 model has been discontinued, but the Phantom 4 RTK is still available at a considerably higher price $5,600. As described on the company website, this drone is “the most compact and accurate low altitude mapping solution.” According to the drone girl, “RTK stands for “real-time kinematic,” and is used about a satellite navigation technique that can enhance the precision of position data derived from satellite-based positioning systems such as GPS, GLONASS. We’re talking centimeter-level precision.” This seems like a needed feature when it comes to doing accurate measurements of buildings for new construction, renovation, and redesign.

1. Matrice 200 V2 - (https://www.dji.com/matrice-200-series-v2) This bad boy has a starting price of around $6,700, and what jumps out at us immediately is the dual gimbal, which thus supports two pieces of equipment. That way, you could be flying with a standard camera and another infrared or other specialty cameras. This drone also boasts the ability to carry two batteries which significantly extends its flight time. According to Vertigo Drones, this system has the following intelligent control features:

• Transmission - Enjoy a more reliable and stable flight with the new OcuSync 2.0 system, which supports automatic dual-frequency band switching and extends flight range to up to 8km (4.97 miles).

• Calibration - When multiple payloads or third-party payloads are installed, users can readjust the drone’s center of gravity in the DJI Pilot app, enhancing flight performance and safety.

• Discreet Mode - When the situation calls for unobtrusive drone operations, especially at night, all lights can be completely turned off in the DJI Pilot app.

• Data Accuracy - The TimeSync system continuously aligns the flight controller, camera, GPS module, RTK module for the M210 RTK V2, as well as payloads or onboard accessories. The position data is fixed to the center of the CMOS for precise geotagging when using DJI payloads.

4. Yuneec H520 (https://us.yuneec.com/h520-series/) or the 3DR H520-G - (https://3drobotics.com/products/hardware/). If you did not know, DJI dominates the field of multirotor UAVs, as is evidenced in the list of options so far. However, we decided to profile another company’s drone for Industrial and Commercial operations, the H520 series from Yuneec. We also note a system produced by 3D Robotics in Berkeley, California, which starts with the Yuneec hardware, which is then flashed, and 3DR uses proprietary software for running the drone, which does, in essence, not talk to Chinese servers. This may be a concern in some sensitive government or military installations and thus be advised depending on where the work will occur. 

The Yuneec 520’s top-of-the-line system is the H520E-RTK which retails for $5,299. From their company website the “The H520E/520 is designed with the inspection industry in mind with six-rotor systems that allow for stable, precise flight, long focal-length lenses that allow the sUAS to fly at a greater distance from an object and data storage that may be shared instantly from the ST16S/E Ground Station or delivered directly in 4K/2K/HD video or 20 Mp still images.”

In the end, it is also essential to know what kind of software integration you need for your final product. Please make sure the software and the hardware you are using will provide data that can easily flow into your BIM or 3D rendering software. Happy mapping!