Stereo vs Single Camera: Decoding Underwater Photogrammetry

Written by Patricia Sestari

February 5, 2024


In the fascinating realm of underwater exploration, the demand for precision and accuracy in mapping submerged environments is ever-growing. Voyis, at the forefront of innovation, specializes in underwater optical systems, including laser scanners and survey cameras. One key element that stands out in the field of underwater photogrammetry is the utilization of stereo cameras. In this blog post, we will dive into the depths of stereo cameras and explore their benefits in comparison to single cameras for underwater photogrammetry. 

Understanding Photogrammetry 

Photogrammetry, the science of making measurements from photograph images, plays a pivotal role in underwater exploration. By capturing detailed images of underwater structures, photogrammetry enables the creation of accurate and colourized 3D models, aiding in various applications such as marine archaeology, environmental monitoring, and underwater infrastructure inspection. 

The Power of Stereo Cameras 

Stereo cameras, equipped with two cameras mimicking the human eyes, bring a new dimension to underwater photogrammetry. Here are some key benefits of using stereo cameras in this context: 

Directly Scaled 3D models 
  • A calibrated stereo camera generates directly scaled 3D models without any additional inputs. The 3D models generated are dimensionally accurate because the stereo-calibration accurately determines the relative position of the two cameras. 
  • Single monocular camera photogrammetry has no scale, and dimensions are only defined relative to each other. Accurate scale is only provided if scale bars, or known dimensions, are added to the survey environment. 
Real-time Depth Perception: 
  • Unlike single cameras, stereo cameras capture images from two slightly different perspectives. This disparity allows for precise depth perception, facilitating the creation of directly scaled 3D models with accurate spatial information. 
  • The use of a stereo camera enables depth maps, a 3D representation of the scene, to be generated in real-time for navigational aiding and manipulator feedback 
  • Improved depth perception is crucial for mapping underwater structures, as it enhances the overall accuracy of the photogrammetric reconstruction, and features tracking on the target. 
Enhanced Accuracy and Resolution: 
  • Stereo cameras provide higher accuracy and resolution compared to their single-lens counterparts. The dual-camera setup captures more information, resulting in detailed and finely resolved images. 
  • This increased level of detail is particularly beneficial in underwater environments where visibility may be limited, ensuring that every feature is captured with utmost clarity. 
Reduced Ambiguity: 
  • In complex underwater scenes, a single camera may struggle to discern between overlapping structures or surfaces. Stereo cameras, with their dual-perspective approach, help reduce ambiguity in feature matching by providing additional information to the photogrammetric software. 
  • This reduction in ambiguity contributes to more accurate and reliable 3D reconstructions of underwater scenes. 
Improved Georeferencing: 
  • Stereo imagery aids in better georeferencing of underwater models. The dual-lens setup allows for precise triangulation, enabling the integration of underwater photogrammetric data with geographical coordinates. 
  • Accurate georeferencing is essential for applications such as underwater mapping, environmental monitoring, and habitat analysis. 

In the world of underwater photogrammetry, the benefits of employing stereo cameras are evident. Voyis, with its expertise in underwater optical systems, recognizes the importance of leveraging advanced technologies to enhance the accuracy and efficiency of underwater exploration. By embracing stereo cameras, researchers, archaeologists, and surveyors can unlock the mysteries of the deep with unprecedented precision, contributing to a better understanding of our underwater world. 


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