How UAVs are Revolutionizing Photogrammetric Mapping

photogrammetric map from a UAV

Photogrammetry – the art of turning remotely sensed data sets into comprehensive models of the earth’s surface and terrain. With the introduction and gradual evolution of Unmanned Aerial Vehicle (UAV) technology, the high-resolution orthomosaics and Digital Elevation Models (DEMs) this process yields are becoming more accessible and higher in quality. With UAV-sourced imagery, you can enjoy a greater level of detail in your resulting models and better leverage AI-driven analysis for superior object classification and change detection.

Photogrammetric Mapping Made Easy With UAVs

Historically, photogrammetry has been a daunting process. To generate valuable models – such as orthomosaics or DEMs – across vast areas, you would have to contract an expensive survey of the area by satellite systems up in space. Additionally, capturing the necessary visual input to build detailed 3D models of the surface and terrain required the implementation of highly specialized radar and LiDAR sensors.

Today, companies demand higher-quality aerial imaging to solve the complex challenges they face. UAVs offer a far simpler deployment alternative, that is lower in cost and results in higher-quality models in comparison to a satellite. While LiDAR sensors are still necessary for 3D models requiring the utmost accuracy of measurements, images from a simple UAV-mounted camera can be used to create photogrammetric 3D models that offer all the detail you need for your operation.

Why Shift From Satellite Technology?

A satellite’s position – out in space orbiting around the Earth – is both its greatest strength and its greatest weakness. Satellites excel at rapidly scanning a vast area, and thanks to their high-speed orbit, they are capable of gathering data quite often. However, because of the Earth’s rotation, it can take a few days for a satellite to revisit a location. Plus, in their north-to-south polar orbit, it can become burdensome to capture imagery of long-ranging east-to-west corridors. You might wind up waiting a long time for the survey to complete. In other words, it’s not easy to use a satellite for a rapid response scenario.

Satellite data also comes at a price premium, and for smaller-scale operations, it quickly becomes cost-prohibitive. You’re usually looking at a minimum purchasing order of approximately 60 miles, sometimes more.

And remember, lots of data doesn’t equal actionable data. Of all the systems used to capture imagery from above, satellites tend to offer the lowest spatial resolution – which means less accuracy and detail in the subsequent model. This is fine when you’re just looking to gain a rudimentary understanding of the environment and topography of an area, but you may be missing out on actionable insights.

Not to mention, you’ll only be able to capture this data when the sky is clear because far above the Earth’s atmosphere, a satellite is totally at mercy to weather elements such as cloud cover. Also, when you’re dealing with a difficult area that requires a specific perspective or optimal time of day, satellites have little room to adjust. As your requirements become more particular – an elevation angle right-above your target, a minimum sun elevation to minimize shadows – satellite companies may deem your request unfeasible or require you to pay an additional priority charge to jump the queue.

UAVs address many of a satellite’s shortcomings in photogrammetry applications:

  • Operational flexibility to accommodate missions-on-demand
  • Deploy at the specific times of day that will yield the best results
  • Scalable systems that can accommodate both small and large-scale mapping
  • Low altitude aerial scanning ensures visuals will not be compromised by cloud cover
  • Maneuverability to map areas at the elevation angle you require

And if you’re not a UAV expert don’t worry, there are a number of great reasons to and outsource UAV monitoring to professional service providers.

Greater Resolution = Greater Insight

Want to know the most important advantage of all? UAVs offer the best spatial resolution and accuracy of aerial imagery available today. On the resolution side, a picture taken from a UAV can capture detail down to an inch or less, whereas satellites can only offer over a foot at best. On the accuracy side, a UAV also has the advantage, especially when equipped with precise RTK GPS navigation systems. A satellite orbits over 300 miles above the earth, travelling at 17,000 miles an hour – this makes accurate positioning an extremely difficult affair. In particular, the sheer distance a satellite is away from its target leads to inaccuracy due to variable topography and angle distortions on the outer areas of an image. Because of their low altitude and capability for low-speed surveys, UAVs can gather far more accurate visual data.

What does this mean for you? Well, if you’re trying to leverage these aerial insights to monitor for specific anomalies, objects, or changes – this high-quality UAV-sourced data is going to fuel much better insights in your resultant models.

Say you’re performing a power transmission line inspection, trying to identify vegetation encroachment along your line. In a 2018 study, comparing UAVs and satellites in a vegetation mapping scenario, the UAV’s higher resolution and image precision yielded far superior 3D point cloud models, that allowed for accurate estimates of tree characteristics such as height and crown diameter.1

The Artificial Intelligence Edge

Are you daunted by the idea of analyzing thousands of images from an aerial inspection? Well, you don’t have to be, because UAV-sourced imagery is perfect for the application of AI-driven computer vision analysis. In the same study mentioned above, machine-learning algorithms fared far better in object and pixel-based classification of vegetation when working from high-quality UAV images 1. These AI systems use a neural network that mimics our brain’s visual cortex for analysis. In other words, it can visually perceive things just as well as the rest of us, except it doesn’t need five coffees over the course of the data to stay focused.

The advantage of applying AI analysis to your orthomosaics and DEMs extends far beyond simple object detection. A highly-autonomous UAV can source data on a routine basis, and with new survey data continually feeding in for analysis, AI can identify changes to provide you with insights that could easily go unseen by the human eye. With this process in place, you drive the actionable data needed to unlock predictive analytics.

Photogrammetric mapping doesn’t have to be a complex and cost-prohibitive process. UAVs are making high-quality orthomosaics and DEMs more accessible than ever before, and are capable of delivering superior visual insights that drive meaningful decision-making. Consider the impact this revolutionary geospatial data could have for your organization.

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  1. Advantage of using drones over spaceborne imagery in the mapping of mangroves, Monika Ruwaimana et al., 2018