Since the early days of taking photos from hot air balloons and kites, aerial cameras have evolved and remain an essential tool within the surveying and mapping industry.
They enable surveyors to capture high-resolution imagery from elevated perspectives, enabling comprehensive data collection and analysis.
These sophisticated devices are instrumental in various applications, from urban planning and environmental monitoring to infrastructure inspection and land surveying.
This article delves into the intricate workings of aerial cameras and their pivotal role in aerial surveying, exploring the use of different camera types, the distinction between aerial photography and photogrammetry, how color filter arrays work and their use in aerial surveys, the synergy between aerial cameras and lidar technology, and the advantages of nadir and oblique imagery.
We will also address the pitfalls and challenges that need to be considered when using aerial cameras in surveying endeavors.
Aerial cameras come in various types, each tailored to serve different purposes in aerial surveying.
For example, drones are often equipped with compact and lightweight cameras that are ideal for small-scale mapping and rapid response scenarios.
Helicopters and fixed-wing aircraft are able to fly more sophisticated medium or large format cameras.
These cameras are optimized for capturing imagery over larger areas, at high altitudes, and with greater detail. They can accommodate a range of lenses and sensors, including multispectral and thermal options, to cater to specific surveying needs.
Helicopter-mounted cameras are versatile, able to hover or fly slowly for detailed data acquisition, while fixed-wing aircraft are better suited for large-scale surveys that cover vast regions.
A crucial distinction to be made in the realm of aerial surveying is between aerial photography and aerial photogrammetry.
While both involve using aerial cameras, they serve distinct purposes and involve different processing methodologies.
Aerial photography focuses on capturing high-resolution images or videos for visual inspection and documentation.
These images are not necessarily calibrated for precise measurements. Aerial photographers typically aim to produce striking visuals, which can be valuable in fields like marketing, media, and environmental monitoring.
In contrast, aerial photogrammetry is a science that leverages the principles of geometry and mathematics to convert 2D or 3D imagery into precise geospatial data.
Aerial photogrammetry relies on the use of highly calibrated cameras to ensure that the captured imagery can be used for accurate mapping and measurement.
This method is essential for applications such as topographic mapping, land surveying, and infrastructure assessment, where precise measurements are imperative.
A color filter array (CFA) is a pattern of color filters placed over the individual pixels of an image sensor in digital cameras. The primary purpose of a CFA is to enable the camera to capture color information in a manner similar to how the human eye perceives color. Each pixel on the sensor is typically covered by one of the color filters, which can be red, green, or blue (RGB), in varying combinations depending on the specific CFA pattern.
The importance of a CFA for how aerial cameras work lies in its ability to:
Pan sharpening and the Bayer pattern are essential techniques used in conjunction with aerial survey cameras to enhance the quality and accuracy of imagery.
Pan sharpening involves fusing high-resolution panchromatic (pan) imagery with lower-resolution multispectral (color) imagery.
A panchromatic sensor captures high-resolution imagery while other panchromatic sensors with color filters on the lens provide the color information to produce the final image.
This fusion leverages the superior spatial detail of the panchromatic channel and the spectral richness of the multispectral channels, resulting in high-resolution, full-color imagery that aids in precise land cover classification, vegetation analysis, and feature identification. The Vexcel Ultracam Eagle line of cameras use pan sharpening technology.
The Bayer pattern, named after its inventor Bryce Bayer, consists of a mosaic of red, green, and blue color filters laid over individual pixels on an image sensor.
The arrangement typically follows a 2x2 repeating grid, with twice as many green filters as red and blue ones. The green filters are more prevalent because human vision is more sensitive to green light.
This pattern is used to capture color information in digital photographs, and it requires a process called "demosaicing" or "debayering" to interpolate the missing color data for each pixel. This interpolation is essential for generating full-color images from a sensor's output.
It enables the camera to capture color information by overlaying red, green, and blue filters on individual pixels of the sensor.
This combination results in color-enhanced, high-resolution imagery that is crucial for accurate mapping, land surveying, and other geospatial applications. All of our Phase One cameras utilize Bayer pattern technology.
Aerial surveying often requires the integration of various technologies to achieve comprehensive results.
One such synergy is between aerial cameras and lidar technology. Lidar involves the use of laser pulses to measure distances and create detailed 3D point clouds.
When combined with cameras, it provides a comprehensive data set that includes both imagery and highly accurate elevation data.
This fusion of aerial survey cameras and lidar is particularly useful in applications like forest management, urban planning, and powerline inspection. The combination allows for a more in-depth understanding of the surveyed area, enabling precise modeling and analysis.
Imagery can be captured from different angles, and this versatility is leveraged in aerial surveying to provide a more comprehensive perspective of the surveyed area. Two primary perspectives are nadir and oblique imagery.
Nadir imagery is captured directly below the aircraft, providing a top-down view. This perspective is essential for precise mapping and orthorectification as it minimizes distortion.
It is commonly used in applications that require accurate georeferencing, such as land surveying and infrastructure inspection.
Oblique imagery, on the other hand, is captured at an angle, providing a broader view of the area.
While it may introduce some distortion, oblique imagery is invaluable for visual inspection and 3D modeling. This perspective is useful in applications like disaster assessment, real estate marketing, and cultural heritage preservation.
Despite their myriad advantages, aerial cameras come with their set of challenges and pitfalls. These include:
Aerial camera systems used for photogrammetry generally include the camera body, a lens with a focal length suitable for the project requirements. You may also need a flight management system and a controller to trigger the camera. If you are using a large-format camera, you may also need a gyrostablized mount.
Our clients flying manned aircraft are often using helicopters with aerial cameras mounted on the nose or carried in a pod. We also see medium format cameras integrated with lidar systems and mounted into a camera hatch, often in single or twin engine aircraft with single or double camera hatches.
For surveying, our clients use medium or large-format cameras with or without lidar. Some projects may require specialized cameras such as multispectral or thermal cameras.
Aerial photographs may be captures as nadir (or vertical) images, in which the camera lens is directed straight down at the ground. Or, images may be captured at an oblique angle, which is often used when mapping urban structures or when doing corridor mapping.
In conclusion, aerial cameras are the cornerstone of modern aerial surveying, offering versatility, precision, and an array of options to cater to diverse applications.
Whether mounted on drones, helicopters, mobile mappers, or fixed-wing aircraft, these sophisticated devices enable professionals to capture high-quality imagery for mapping, measurement, and visualization.
At AERIALSURVEY.com, we carry new Phase One medium format aerial survey cameras as well as many used camera systems and parts. We also offer large format aerial cameras for both nadir and oblique imagery.
Be sure to contact us if you have any questions about what aerial survey camera might best suit your projects.