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Perspective of Image Preprocessing on Image Processing
Published in Jyotismita Chaki, Nilanjan Dey, A Beginner's Guide to Image Preprocessing Techniques, 2018
Jyotismita Chaki, Nilanjan Dey
Image corrections are generally grouped into radiometric and geometric corrections. Some standard correction methods might be completed prior to the data being delivered to the user [5]. These techniques incorporate a radiometric correction to correct for the irregular sensor reaction over the entire image, and a geometric correction to correct for the geometric misrepresentation owing to different imaging settings such as oblique viewing [6]. Radiometric correction means correcting the radiometric error caused owing to the noise in the brightness values of the image. Some common radiometric errors are random bad pixels or shot noise, line start/stop problems, line or column dropouts, and line or column striping [7]. Radiometric correction is a preprocessing method to rebuild physically aligned values by altering the spectral faults and falsifications caused by the sensors themselves when the individual detectors do not function properly, or are not properly calibrated for the sun's direction and or landscape [8]. For example, shot noise, which is generated when random pixels are not recorded for one or more band, can be corrected by identifying missing pixels. Missing pixel values can be regenerated by taking the average of the neighboring pixels and filling in the value of the missing pixel. Figure 1.2 shows the preprocessed output.
Sources, Detectors, and Recording Media
Published in Rajpal S. Sirohi, Introduction to OPTICAL METROLOGY, 2017
This chapter deals with the sources of radiation and the detectors that are used in optical metrology. The light incident on the object is to be measured. Radiometry refers to the measurement of radiation. This includes the wavelength range from 10 nm to 1,000 μm, the regions commonly called ultraviolet, visible, and infrared. On the other hand, photometry refers to the detection of light in the visible spectrum, that is, the part of the electromagnetic spectrum to which the eye is sensitive. This corresponds to the wavelengths in the range from 360 nm to 830 nm. Radiometry includes the complete optical spectrum, whereas photometry is limited to the visible spectrum as defined by the response of the eye. To compare light sources, a brief description of radiometric and photometric units is given here.
Stratigraphy
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Geochronology is a general term for investigations of the age of rocks, fossils, and other geological specimens and of key events in Earth history. These investigations rely heavily on radiometric dating—a method of determining how long ago a rock formed or an event occurred based on the discovery that radioactive (parent) atoms decay at constant rates to different atoms, called daughter atoms. Early interpretations of geologic time were based mostly on fossils, which led to limitations because many of the oldest rocks on Earth typically contain no fossils. In contrast, radiometric dating can be applied to many igneous and metamorphic rocks of all ages (although not as successfully to sedimentary rocks).
Loss of mangroves as a consequence of the anthropic interactions downstream a river basin
Published in Journal of Ecohydraulics, 2023
J. G. Ramos, J. Gracia-Sánchez, L. Marrufo-Vázquez
To identify most of the changes, RS techniques have demonstrated to be an efficient tool applied to satellite imaging, in this case, to Landsat images. The pre-processing of the images consisted of atmospheric and radiometric correction (geometric correction was not necessary). The atmospheric correction was carried out by using the Cloud Masking for Landsat module from QGIS (2019). The radiometric correction is the calculation of the radiance from the digital levels of the scenes and the reflectance values (USGS 2019). Using the mosaic module from ERDAS (2019) different paths and rows (35/39 and 35/40) were combined, except for the 1983 image where there is only scene 35/39. The types of land use that were determined in this study were related to the decrease in forest and mangrove coverage (Kovacs et al. 2001) due to anthropogenic economic activities such as agriculture and livestock (grass-lands) as shown in Table 2.