The major sources for distortion of underwater images are light scattering and color change. This leads to one color dominating an image. Water has high refractive index when compared to air. Therefore when light is incident on water, it gets refracted. Hence, underwater images suffer from limited range visibility, low contrast, blurring, color diminished and noise. One method of improving the image quality is by image enhancement. This paper presents a comparative study of various image enhancement techniques used for enhancing underwater images. Index Terms—Color change, light scattering, underwater image, image dehazing, RGB, HSI, CMY, histogram equalization [1]INTRODUCTION Image processing is a form of signal processing in which input is an image and the output is either an image or a set of characteristics or parameters related to the image[1]. It deals with the processing of a 2D image by the help of a computer. The smallest element of an image is a pixel, also known as picture element. The processing of an image in done pixel by pixel. Two methods of improving image quality is by image restoration and image enhancement. Image restoration: It deals with filtering the observed image to minimize the effect of degradations. The effectiveness of image restoration depends on the extent and the accuracy of the knowledge of degradation process. Image restoration differs from image enhancement. Image restoration is based on more extraction of image features. The image restoration aims to recover a degraded image using a model of the degradation. These methods require many model parameters like attenuation and diffusion coefficients that characterize the water turbi... ... middle of paper ... ...ater image enhancement techniques provide a way to improve the object identification in underwater environment. There is a lot of research started for the improvement of image quality, but limited work has been done in the area of underwater images. Histogram Equalization is one of the well-known image enhancement for contrast enhancement because it is simpler and effective. Basic idea of HE is to re-map the gray levels of an image. It tends to introduce some annoying artifacts and unnatural enhancement. Though CLAHE is used to minimize the effects, it is very time consuming. The technique which uses filters makes use of four filters sequentially. It is very complex and time consuming. Hence, contrast stretching using color models is used for Image enhancement which is the simplest of all the techniques discussed in the paper. It is easy and simple to implement.
Therefore, LADS must be flown during hours of darkness to eliminate the errors caused by the reflection of the sun off the water, which return false reading to the aircraft causing inaccurate depth. To calculate the green beam (which travels to the seabed and back up) you must obtain the speed of light in water which is given by Maxwell?s equations which basically show that when passing through a transparent or translucent material medium, like glass or air, light will have a slower speed than in a vacuum. Therefore, the extra time and distance traveled by the green pulse can be calculated, giving the depth of the water. The aircraft needs to use two beams to ensure that the pulses return to the aircraft. In certain situations the pulse may not return to the aircraft due to flat glassy water surface (because of the law of reflection).
This technique a significant difference in limit of detection and the required time for analysis when it compared with number of other technique.
Sonar is an acronym for sound navigation and ranging meaning that sound waves are used to move around and determine the distances between objects. Sonar is a crucial component to many seaworthy vessels. Civilians use it to map the ocean floor, determine water depths, find fish, and locate underwater objects such as pipelines, wrecks and wellheads. Naval uses are to find torpedoes, submarines, sea mines, swimmers, acoustic mines, and navigation. Sound is much more efficient underwater, traveling at a 3,403.5 miles per hour (mph), while only traveling at a meager 769.5 mph through the air; sometimes sound can travel even faster depending on temperature, salinity, density and pressure (Encyclopedia of Marine Science pg. 497). This is due to the close association of between water molecules. Sound is an out...
The navy adopted the technology for use by submarines to detect objects in the water.
4) Every time I used to see a scattered image and not realizing what the image was at first, but after spending time seeing it and finally getting a picture I never knew that its was a part of processing. The type of process that takes place when not being aware of something, but after consi...
Archaeology is a continuously evolving field where there is a constant stream of new branches and excavation methods. Due to the influx of new technologies and innovations in recent decades, archaeologists have been able to excavate previously inaccessible areas. For example, new diving equipment and tools such as proton magnetometers, side-scan sonar, sub-bottom profiler, and miniature submarines have allowed archaeologists to dive into the deep depths of the ocean. As a result, the branch of underwater archaeology was created to search for shipwrecks and other artifacts on the ocean floor. Underwater archaeology’s role has increased in recent years as it allows archaeologists to more accurately interpret the past by supplementing information gained through traditional land excavations.
Essentially, once an image exists in digital form, it can either be tweaked to adjust even its most indiscernible features or it can be entirely morphed into something altogether different. There ...
the different methods, and in recent developments we are learning that the main reason for
The large width Gaussian masks are not preferred as detector's sensitivity to noise is low and moreover, the localization error in the detected edges also increases with increase in Gaussian mask width. Step 2:- After the initial pre-processing steps of smoothening and removal of noise, the edge strength is calculated by taking the gradient of the image. For the purpose of edge detection in an image, the Sobel operator first performs a 2-D spatial gradient measurement with the help of convolution masks. The convolution masks used are of the size 3X3, where one is used to calculate the horizontal gradient(Gx) while the other is used to calculate the vertical gradient(Gy). Then, the approximate absolute edge strength can be calculated at each point.
I have been waiting for such a perfect opportunity to purchase my dream computer; the MacBook Pro, manufactured by Apple that weighs 2.02 kg. Getting the right specification was the breakthrough because, even more, my desire for the 15-inch laptop computer. The 15-inch computer has over 5 million pixels, which gives it a stunning look, with images taking a new level of pragmatism. It has an impressive 2880-by-1880 resolution that enables the eyes to view more of high-resolution images. Besides, it has a Retina display , which minimizes glare, maintaining an incredible quality and color. As a result, the high contrast ratio makes black images look blacker while white images look whiter. The inclusive IPS technology allows the user to view everything on the screen at a 178-degrees angle.
Image intensification is the process of converting x-ray into visible light. “Early fluoroscopic procedures produced visual images of low intensity, which required the radiologist's eyes to be dark adapted and restricted image recording. In the late 1940s, with the rapid developments in electronics and borrowing the ideas from vacuum tube technology, scientists invented the x-ray image intensifier, which considerably brightened fluoroscopic images” (Wang & Blackburn, 2000, np). We will explore the image-intensification tube, the various gain parameters associated with the tube, and the magnification mode of the image intensifier.
The final step is called rendering. During rendering, the computer calculates the effect of light, color, and texture on the model's surface. For a film or video, the computer will produce a two-dimensional digital picture of the characters for each frame of the animation. The computer artist usually adjusts many visual effects, such as camera focus and transparency, during the rendering phase.
How would you go about mapping sea floor when visual methods are impaired with the inability of light to penetrate water? Use a different method to measure it, using a wavelength that can penetrate the depth of the sea. Sound waves can penetrate the deepest depths of the ocean using special equipment produced by the military and commercial companies such as sonar to measure the ocean bottom.
Water quality can be described as the measurement of the condition of water relative to the requirements of humans, animals and plant’s need. When we talk about water quality testing, we are highlighting a critical piece of natural observing for civil engineers in order to create a specific structure or decision. At the point when water quality is poor, it influences almost every single form of life in our planet; going from plants to animals and thereon. Hydrology, in the other hand, is the study of water. It is important to state that hydrology is a critical part for civil engineers to determine and predicting decisions that will affect our biological environment.
The first step is to transform the signal from analog to digital, if the camera itself is not digital already. The data is then processed and based on the results certain actions are taken. The processing occurs in the camera itself, if required hardware for this is built in, or the data is sent to a computer.