Answering one of our most commonly asked questions isn't always easy, but we do try! 📏
While identifying and counting the animals in our videos is relatively straightforward, determining their size is much more difficult. Although the zoom angle of the camera can be calculated, the distance between the camera and the animals is usually not known, and accurate size measurements can’t be made.
The first approach we used to solve this problem was to mount two parallel lasers on our remotely operated vehicle's camera, aimed in the direction that the camera is looking. Because the distance between the lasers is known (typically 29 centimeters or about one foot), the two laser dots on the seafloor provide a size reference to which seafloor animals can be compared and measured.
Another useful measuring tool—Laser Measure—uses three lasers aimed in a helical pattern to create three laser dots on the seafloor. If we assume that the seafloor is flat, as it is for most of the areas we study with video transects, then the locations of the three laser dots in the video images can tell us the distance and the orientation (i.e., tilt) of the seafloor. Given these parameters, we can measure the size of any object in the image regardless of its location or orientation in the image. Learn more about this handy tool on our website.
