Perspective is crucial and, for a long time, humans were only able to see the earth from our perspective on the ground. With the advent of various forms of air travel, and the development of high-resolution imagery, that changed. Being able to capture high resolution aerial imagery has given us a fresh perspective of our world, enabling us to gain new knowledge and understand our environment better.
The first aerial image was taken from a hot air balloon in 1858. Since then, aerial images have been taken from planes, satellites, helicopters, and – more recently – unmanned aerial vehicles.
Aerial imagery has advanced greatly and is used for a wide range of applications, from high resolution inspection systems to precision agriculture.
In this article, we’ll take a look at different aspects of aerial imagery, from classification to its applications.
Aerial or Satellite?
Aerial images are taken from drones, balloons, airplanes or helicopters while satellite images are taken from satellites that orbit the earth.
These two types of images differ in their resolution and in the range they cover.
Satellite imagery has a high temporal resolution. Satellites typically go over the same place repeatedly as they circle the world. They are therefore great for applications that need to analyze the changes in an area over time.
Aerial imagery has great spatial resolution, chiefly because it is taken from positions that are closer to the ground. It is used when high resolution imagery is required, for example in pipeline and high-value asset inspection.
Classifications and Use Cases of Aerial Imagery Based on Camera Axis
Vertical Aerial Imagery
This is where images are taken along the vertical axis, such that the ground is directly beneath the camera. A small area of the ground is captured and objects such as buildings are captured from directly above.
Vertical aerial images are commonly used for mapping and object detection.
Low Oblique Aerial Imagery
This is where images are taken at around 15 – 30 degrees from the vertical axis. The camera is slightly tilted, resulting in a larger area of the ground being captured in the image.
Low oblique aerial images do not capture the horizon. They are used for the development of three-dimensional imagery.
High Oblique Aerial Imagery
To capture high oblique images, the camera is tilted at around 60 degrees from the vertical axis. The result is that a larger area is covered, including the horizon.
Oblique imagery, both low and high, is used for topographical investigation in archaeology and geology.
Images from different angles can be combined to generate 3D models of a landscape.
Example Applications of Aerial Imagery
The use of aerial imagery has been on the rise, partly due to increased availability. You can now use a drone whereas some years ago, you could only take aerial images by hiring a plane.
Below are some of the use cases that have precipitated the increased use of aerial imagery.
Phenotyping With UAV’s or Drones
Phenotyping is the process of studying the impact that a plant’s genes and the environment it grows in has on the plant’s observable characteristics. Determining that relationship allows for desirable characteristics such as higher yields to be improved and for undesirable traits to be reduced.
Drones have made phenotyping easier. With a drone, you can get closer to vegetation and plants, giving you higher-quality results that yield more insights. It is also more economical to take more trips for imaging, which makes the study more comprehensive.
Power Line Inspection
Drones are particularly good for inspecting power lines. Drones for inspection can be fitted with multiple sensors, allowing phenomena such as corona discharge to be detected automatically.
High resolution inspection systems make it possible to create digital twins of power lines. The digital twins can be fed into artificial intelligence-driven software for further analysis and automatic inspection.
Conclusion
Aerial imagery has grown more versatile over the years, allowing a wide range of applications across industries.
Aerial images can be classified into multiple types according to the angle of the camera, with each type being most suitable for a particular use case. In some use cases, such as the generation of 3D models, different types can be combined.
Drones for inspection have become especially popular. They are used for applications such as power line inspection and pipeline and high-value asset inspection.
