Mapping vast underwater areas through imaging technology holds remarkable promise for enhancing our understanding of the ocean. In this segment of the ‘Color Imaging Series,’ Voyis explores how underwater surveyors, researchers, and naval forces can leverage advanced terrestrial photogrammetry software by integrating pre-processed Voyis images, resulting in stunning true-color imaging capabilities.
Understanding Photogrammetry
Photogrammetry is both an art and a science focused on deriving three-dimensional data from photographs. This technique involves capturing overlapping images of an object, structure, or habitat and transforming them into 2D or 3D digital representations.
While photogrammetry is widely used in terrestrial applications, particularly with drones, its underwater applications are gaining traction due to the increasing need for precise underwater mapping and modeling. This technology is becoming essential for environmental monitoring, marine archaeology, salvage operations, and inspections of subsea infrastructure.
With detailed 3D models or 2D maps, underwater sites such as shipwrecks can be documented for reconstruction; bridge supports can be assessed for maintenance; offshore facilities can be mapped; and areas can be monitored over time to identify environmental changes.
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How Voyis is Pioneering Underwater Imaging
The potential of wide-area underwater imaging is immense, offering surveyors, researchers, and naval forces a deeper insight into this largely unexplored domain. To facilitate this, Voyis has tackled historical challenges that have hindered widespread use, providing an exceptional true-color imaging solution that allows users to seamlessly integrate pre-processed Voyis images into advanced terrestrial photogrammetry software.
Color calibration: In photogrammetry, features in the image sequence are viewed from various angles, leading to changes in perceived color and lighting as the artificial light source shifts. A solution must effectively balance color accuracy and consistency across images.
To tackle this intricate issue, Voyis has created an imaging solution that employs machine learning to develop a color correction model tailored to the specific survey environment.
Once images are consistently adjusted to eliminate the effects of the water medium—such as color distortions and lighting variations—the resulting dataset can be directly utilized in terrestrial photogrammetry software like Pix4D, enabling the creation of notable wide-area image maps (orthomosaics) and 3D models.
Uniform Lighting: Another significant challenge in photogrammetry is achieving consistent illumination across the entire camera field of view. This uniformity is crucial for both the visual quality of the images and the accuracy of the resulting 3D models, ensuring that features are detectable throughout the entire imaging area.
Voyis imaging systems adopt a dual approach to address uneven lighting, combining physical design elements of our NOVA LED panels with algorithmic lighting corrections.
Consistent Focus: Manny underwater cameras rely on auto-focus to adjust image clarity as the scene changes during a survey. However, this method presents two main challenges that can negatively impact photogrammetry: focus inconsistency and camera calibration issues.
When auto-focus is used in complex environments, the focus algorithm may lock onto different features in sequential images, leading to noticeable variations in overall focus. This inconsistency complicates the ability of Structure from Motion (SFM) to match features across frames. Additionally, changes in focus distance can alter the camera’s parameters, resulting in an inaccurate undistortion model that diminishes the precision of photogrammetric 3D models.
Voyis has determined that utilizing Fixed Focus lenses is the optimal solution for reliable image capture, as thay maintain consistent camera calibration and are less susceptible to mechanical vibrations.By carefully calibrating the fixed focus distance, it is indeed possible to achieve uniform focus across the field of view and an effective depth of field for typical imaging scenarios.
Access the complete white paper on Voyis’ website >>
