UltraMap Radiometry: Key strategies for exceptional aerial imagery
14 August 2024
Enabling our customers to deliver the highest data quality with a high level of automation, embedded within an easy-to-use workflow, has always been our primary goal in developing the UltraMap Software suite. While creating and verifying high-quality geometric results is relatively straightforward, achieving good radiometric quality, on the other hand, is more complex. This complexity arises from the general challenge that color is inherently subjective, meaning different people see it differently. In addition, current tenders often struggle to define meaningful quality parameters to work against.
In this blog, we will delve into the challenging field of radiometric processing and how the UltraMap and new tools from version 6.4 can help fulfill even the most demanding requirements.
The old saying, "the better the input, the better the output," holds true when considering the basic quality fed into the radiometric workflow. The quality of the initial data collection sets the stage for the final output. A good data collection setup involves, first and foremost, using a high-resolution, well-maintained, stable camera with precise calibration. Additionally, it’s important to collect data under consistent atmospheric conditions and avoid extreme variations, such as those between different seasons like summer and fall, which can present significant challenges and impact overall quality. High-altitude captures, which involve a significantly larger amount of atmosphere between the camera and the ground objects, require special approaches to ensure the best possible data quality. Ensuring consistent lighting conditions and minimizing shadows and reflections can also contribute to more reliable and high-quality data for the radiometric process.
UltraCam aerial camera systems are precise measuring instruments that capture millions of images across the world annually. To ensure these insights are truly meaningful, UltraCams are designed to maintain precision and consistency in their measurements at all times.
Kicking off with TPP in UltraMap: The first step to success
In the journey from raw data to final output, one of the first critical steps happens within UltraMap Essentials during the post-processing phase, thanks to our True Pixel Processing (TPP) approach. This proprietary method is designed to preserve all pixel information from the moment of initial exposure through to the final data products, all while maintaining the exceptional image geometry that UltraCams are known for. For a deeper dive into TPP, we encourage you to explore our previous blog posts:
A key component of TPP is Adaptive Motion Compensation (AMC), our cutting-edge solution for multi-directional and scene-aware motion blur removal. AMC is designed to eliminate all motion blur, regardless of direction, ensuring that every image remains consistently sharp across the entire project. Because motion blur can vary with each shot, AMC dynamically adapts to each image, delivering uniformly high-quality results. For more on AMC, check out our detailed scientific paper here.
Advanced UltraMap radiometry tools for a wide range of user preferences
The past releases of UltraMap have already featured significant improvements in the radiometry stage, such as the new water handling introduced in version 6.0. These enhancements are essential additions to the already well-established radiometric workflow, which includes tools like automated color balancing, Levels and Gamma settings, and more.
The capabilities in UltraMap are so diverse because the requirements and preferences of end customers vary greatly, and there is no single "correct" image when it comes to radiometric properties. Expectations range from requests for super balanced aerial imagery with low contrast, well-lit shadows, and well-handled highlights, to very contrasty, vibrant imagery.
The shadows and highlights in this image are well balanced to facilitate the visual interpretation of the aerial image.
Maintaining radiometric consistency: Techniques for long-term data integrity
Nevertheless, there are common grounds such as achieving realistic colors, imagery that is free of color cast, and radiometry that remains consistent even when data is collected years apart.
One way to ensure your image is color cast-free is to adjust the Levels and Gamma settings. But how can you confirm that the image is truly free of a color cast?
In the image above, you see that we've placed color targets on the rooftop of our headquarters in Graz during test flights. The gray surroundings on this roof are ideal because they prevent any interference with the color targets. When you look at the histogram of the gray color target, the red, green, and blue channels align perfectly. This happens because gray, black, and white are neutral colors, meaning their color channels have equal values. This alignment in the histogram confirms the absence of a color cast.
The image was captured by the UltraCam Dragon 4.1 with a GSD of 5 cm and is part of the newly released sample data set from this hybrid aerial mapping system.
Enhancing shadows, highlights, and more with UltraMap's Curves Tool
Once this is successfully completed, final adjustments to the radiometry can be made, including shadow and highlight treatment, as well as refining sharpness, contrast, and denoising. The new and improved Curves Tool, introduced in UltraMap v6.3, which allows for the combination of multiple curve adjustments along with shadow and highlight tabs, is a powerful resource for tailoring your aerial imagery to achieve the desired look.
Improving contrast in challenging conditions: UltraMap's new Local Contrast Tool
Especially when brightening shaded areas, the result can sometimes appear a bit dull and less contrasty than desired, depending on the amount of correction applied. To address this issue and still achieve good contrast, we have introduced the new ultra-wide local contrast slider in the Sharpening/Denoising dialog. This tool is also useful for improving high-altitude flight data, where achieving decent contrast can sometimes be challenging.
You are currently viewing a placeholder content from Youtube. To access the actual content, click the button below. Please note that doing so will share data with third-party providers.
More InformationIn conclusion, the advancements in UltraMap, from True Pixel Processing to the final radiometric adjustments, are designed to empower users with the tools necessary to achieve superior image quality across various conditions. UltraMap ensures that even the most challenging radiometric demands can be met. Whether you are striving for consistency in long-term projects or tackling the complexities of high-altitude data, UltraMap provides a robust and flexible solution that adapts to your specific needs, helping you deliver the highest quality aerial imagery every time.
Interested in achieving the highest quality imagery? Explore our latest features or request a demo today!
Get in touch
