Radiometric Method Research Articles

Haze Removal Based on a Fully Automated and Improved Haze Optimized Transformation for Landsat Imagery over Land

Optical satellite imagery is often contaminated by the persistent presence of clouds and atmospheric haze. Without an effective method for removing this contamination, most optical remote sensing applications are less reliable. In this research, a methodology has been developed to fully automate and improve the Haze Optimized Transformation (HOT)-based haze removal. The method is referred to as AutoHOT and characterized with three notable features: a fully automated HOT process, a novel HOT image post-processing tool and a class-based HOT radiometric adjustment method. The performances of AutoHOT in haze detection and compensation were evaluated through three experiments with one Landsat-5 TM, one Landsat-7 ETM+ and eight Landsat-8 OLI scenes that encompass diverse landscapes and atmospheric haze conditions. The first experiment confirms that AutoHOT is robust and effective for haze detection. The average overall, user’s and producer’s accuracies of AutoHOT in haze detection can reach 96.4%, 97.6% and 97.5%, respectively. The second and third experiments demonstrate that AutoHOT can not only accurately characterize the haze intensities but also improve dehazed results, especially for brighter targets, compared to traditional HOT radiometric adjustment.

Determining the Tropospheric Delay of a Radio Signal by the Radiometric Method

We present a method and algorithm for real-time determination of the tropospheric delay of a radio signal and the radiometric complex developed on their basis. The method is based on the measurement of the atmospheric thermal microwave radiation intensity at the frequencies ν 1 = 20.7 GHz, ν 2 = 32 GHz, and ν 3 = 56.7 GHz and solution of the corresponding inverse problem with respect to the atmospheric parameters (temperature, pressure, humidity, and water content) which completely determine the tropospheric delay of a radio signal. The method was experimentally tested by comparing the radio-signal delay series obtained by the radiometric method and the GLONASS/GPS data. The error of determining the wet component of the radio-signal delay was about 3 mm.

Double modulation pyrometry: A radiometric method to measure surface temperatures of directly irradiated samples.

The design, implementation, calibration, and assessment of double modulation pyrometry to measure surface temperatures of radiatively heated samples in our 1 kW imaging furnace is presented. The method requires that the intensity of the external radiation can be modulated. This was achieved by a rotating blade mounted parallel to the optical axis of the imaging furnace. Double modulation pyrometry independently measures the external radiation reflected by the sample as well as the sum of thermal and reflected radiation and extracts the thermal emission as the difference of these signals. Thus a two-step calibration is required: First, the relative gains of the measured signals are equalized and then a temperature calibration is performed. For the latter, we transfer the calibration from a calibrated solar blind pyrometer that operates at a different wavelength. We demonstrate that the worst case systematic error associated with this procedure is about 300 K but becomes negligible if a reasonable estimate of the sample's emissivity is used. An analysis of the influence of the uncertainties in the calibration coefficients reveals that one (out of the five) coefficient contributes almost 50% to the final temperature error. On a low emission sample like platinum, the lower detection limit is around 1700 K and the accuracy typically about 20 K. Note that these moderate specifications are specific for the use of double modulation pyrometry at the imaging furnace. It is mainly caused by the difficulty to achieve and maintain good overlap of the hot zone with a diameter of about 3 mm Full Width at Half Height and the measurement spot both of which are of similar size.

Verification of calibration methods for determining photon-counting detection efficiency using superconducting nano-wire single photon detectors.

In recent years several ways to radiometrically calibrate optical fiber-coupled detectors have been developed. However, fiber-coupled calibration methods for single photon detectors have not been compared by national metrology institutes in order to validate their equivalence or traceability to the international systems of units yet.. Here, we present the comparison of radiometric calibration methods traceable to a NIST cryogenic radiometer at the 'few-photon' level. The calibration methods are based on metrology grade optical power meters. The expanded (k = 2) relative standard uncertainties of the calibration methods for the detection efficiency are of the order of 0.5%. However, the results changed relatively by 10% with a different set of optical fibers and mating connectors. These results stress the importance of fiber-core dimensions and fiber-connector repeatability.

Solvent extraction of Cu, Mo, V, and U from leach solutions of copper ore and flotation tailings

Flotation tailings from copper production are deposits of copper and other valuable metals, such as Mo, V and U. New hydrometallurgical technologies are more economical and open up new possibilities for metal recovery. This work presents results of the study on the extraction of copper by mixed extractant consisting p-toluidine dissolved in toluene. The possibility of simultaneous liquid–liquid extraction of molybdenum and vanadium was examined. D2EHPA solutions was used as extractant, and recovery of individual elements compared for the representative samples of ore and copper flotation tailings. Radiometric methods were applied for process optimization.

Radiometric Identification Based on Low-Rank Representation and Minimum Prediction Error Regularization

Recently, radiometric identification has attracted much attention. Previous research works considered feature extraction and classification separately, which resulted in that the extracted RF fingerprint features may not be good features and not be suitable for a designated classifier. In this letter, a novel radiometric identification method is proposed to improve the performance of radiometric identification. This method attempts to find a low-rank representation matrix of original data and the optimal classifier parameter simultaneously, by imposing a regularization item of minimum prediction error. Since the recovered radio-frequency fingerprint features are discriminative, the proposed method is suitable for radiometric identification. Experiments on real data sets demonstrate that the proposed method not only outperforms the competitive methods with a higher accuracy of radiometric identification but also has a better robustness against noise. The results indicate that the proposed algorithm can discriminate different emitters with high classification accuracy even if they are from the same manufacturer.

NEOGENE AND QUATERNARY CONTINENTAL BIOSTRATIGRAPHY OF GREECE BASED ON MAMMALS

Most basins of Greece were filled with thick Neogene-Quaternary continental deposits, which include a large number of mammal fossiliferous sites. The investigations of the last 40 years in the various basins of Greece led to the discovery of many new fossiliferous sites. The extensive, long time and continuous excavations in the new fossiliferous sites as well as in the previously known ones - like the classical localities of Axios Valley, Pikermi and Samos Island - provided numerous fossils enriching remarkably the Greek fossil mammal record. The systematic study of these collections provided numerous data for their biochronology. Further magnetostratigraphic, radiometric or other methods of absolute chronology provided additional chronological data for the mammal faunas and the corresponding deposits. The correlation of all these data allowed the biostratigraphic classification of the continental Neogene Quaternary deposits of Greece which is given in the biostratigraphic tables of the present article. From these tables it is clear that for some time-intervals (Late Miocene, Early Pleistocene) the data are abundant allowing a detailed biostratigraphy, but for some others (Early- Middle Miocene, Pliocene, and for some time-spans of Early Pleistocene) the data are imited or missing and cannot allow an accurate and complete biostratigraphy.

Historical record of nutrients inputs into the Xin’an Reservoir and its potential environmental implication

The Xin'an Reservoir is an important water supply source and water conservation area for the Qiantang River. However, after the occurrence of the two algae blooms in 1998 and 1999, the safety of water quality has been put into question. In order to study the historical deposition of nutrients, sediment cores were collected in different regions from the Xin'an Reservoir. The stable isotopes δ13C and δ15N, nutrients, total organic carbon (TOC), and inorganic carbon (IC) in the sediment cores were determined. Radiometric methods (210Pb and 137Cs) were used to obtain sediment chronologies. Spatially, it was found that the average total nitrogen (TN) content in the upper 5cm of sediments increased from 0.21% in the riverine zone, to 0.33%, and then to 0.57% in the lacustrine zone. The average TP content in the upper 5cm increased from 0.67gkg-1 in the riverine zone, to 1.03gkg-1 in the estuary region, and then to 1.65gkg-1 in the lacustrine zone. In addition, TOC levels showed a distinct increase from 1.42% in the bottom to 5.97% in the surface of the lacustrine zone. These results demonstrated that although primary productivity and the input of nutrients constantly increased in recent years, algae blooms rarely occurred in the Xin'an Reservoir, due to "depth effect" and an aquatic environment protection-oriented fishery policy. However, high TOC flux and high bio-available phosphorus and nitrogen in surface sediment demonstrated that the reservoir is still confronted with the potential risk of algae blooms.

The DOM Generation and Precise Radiometric Calibration of a UAV-Mounted Miniature Snapshot Hyperspectral Imager

Hyperspectral remote sensing is used in precision agriculture to remotely and quickly acquire crop phenotype information. This paper describes the generation of a digital orthophoto map (DOM) and radiometric calibration for images taken by a miniaturized snapshot hyperspectral camera mounted on a lightweight unmanned aerial vehicle (UAV). The snapshot camera is a relatively new type of hyperspectral sensor that can acquire an image cube with one spectral and two spatial dimensions at one exposure. The images acquired by the hyperspectral snapshot camera need to be mosaicked together to produce a DOM and radiometrically calibrated before analysis. However, the spatial resolution of hyperspectral cubes is too low to mosaic the images together. Furthermore, there are no systematic radiometric calibration methods or procedures for snapshot hyperspectral images acquired from low-altitude carrier platforms. In this study, we obtained hyperspectral imagery using a snapshot hyperspectral sensor mounted on a UAV. We quantitatively evaluated the radiometric response linearity (RRL) and radiometric response variation (RRV) and proposed a method to correct the RRV effect. We then introduced a method to interpolate position and orientation system (POS) information and generate a DOM with low spatial resolution and a digital elevation model (DEM) using a 3D mesh model built from panchromatic images with high spatial resolution. The relative horizontal geometric precision of the DOM was validated by comparison with a DOM generated from a digital RGB camera. A surface crop model (CSM) was produced from the DEM, and crop height for 48 sampling plots was extracted and compared with the corresponding field-measured crop height to verify the relative precision of the DEM. Finally, we applied two absolute radiometric calibration methods to the generated DOM and verified their accuracy via comparison with spectra measured with an ASD Field Spec Pro spectrometer (Analytical Spectral Devices, Boulder, CO, USA). The DOM had high relative horizontal accuracy, and compared with the digital camera-derived DOM, spatial differences were below 0.05 m (RMSE = 0.035). The determination coefficient for a regression between DEM-derived and field-measured crop height was 0.680. The radiometric precision was 5% for bands between 500 and 945 nm, and the reflectance curve in the infrared spectral region did not decrease as in previous research. The pixel and data sizes for the DOM corresponding to a field area of approximately 85 m × 34 m were small (0.67 m and approximately 13.1 megabytes, respectively), which is convenient for data transmission, preprocessing and analysis. The proposed method for radiometric calibration and DOM generation from hyperspectral cubes can be used to yield hyperspectral imagery products for various applications, particularly precision agriculture.

Radiometric methods in the measurement of particle-laden flows

The article discusses a study on hydrotransport of solid particles (ceramic models of polymetallic nodules) in a vertical pipeline using two different radioisotope methods: tracer and gamma-ray absorption. The radiotracer method makes it possible to determine the velocity of selected solid particles representing specified size fractions while the absorption method enables measurement of mean transport velocity of the entire dispersed phase. The measurements were performed with the use of NaI(Tl) scintillation detectors, sealed linear sources of radiation Am-241 with the energy of 59.54keV and isotope Tc-99m with gamma radiation energy of 140.51keV. The experiments were carried out in a pipeline with an internal diameter of 150mm, for three different water velocities in the range of 1.5–3.6m/s and three different sizes of ceramic models with size up to 60mm. Analyses of the detector signals, in measurements based on both tracer and absorption technique, applied cross-correlation function (CCF). It was shown that with the same water velocity different fractions of solid particles have moved with different velocities and the lowest velocities were obtained for the particles with the largest diameters. This enabled interpretation of the CCF in absorption measurements as a distribution of possible interval times for the specific fractions of conveyed particles.

A New Radiometric Correction Method for Side-Scan Sonar Images in Consideration of Seabed Sediment Variation

Affected by the residual of time varying gain, beam patterns, angular responses, and sonar altitude variations, radiometric distortion degrades the quality of side-scan sonar images and seriously affects the application of these images. However, existing methods cannot correct distortion effectively, especially in the presence of seabed sediment variation. This study proposes a new radiometric correction method for side-scan sonar images that considers seabed sediment variation. First, the different effects on backscatter strength (BS) are analyzed, and along-track distortion is removed by establishing a linear relationship between distortion and sonar altitude. Second, because the angle-related effects on BSs with the same incident angle are the same, a novel method of unsupervised sediment classification is proposed for side-scan sonar images. Finally, the angle–BS curves of different sediments are obtained, and angle-related radiometric distortion is corrected. Experiments prove the validity of the proposed method.

Electron spin resonance dating of fossil teeth : some basic guidelines to ensure optimal sampling conditions

Unlike radiometric methods based on the measurement of radioactive growth or decay of isotopes (e.g., 14C, 40Ar/39Ar, 230Th/234U), the application of radiation exposure dating methods (OSL, TL, ESR) requires the acquisition of data from the sample itself, in addition to those related with its surrounding environment. Indeed, for Electron Spin Resonance (ESR) dating of tooth enamel, the origin of the sample as well as its sedimentary context must be well known to ensure an accurate dose rate reconstruction. The systematic record of sampling data in the field appears to be essential for the implementation of the method and thus the calculation of reliable age results. Consequently, we propose here some basic guidelines to help non-dating specialists intending to collect fossil teeth from archaeological or geological context for subsequent ESR dating purposes.

Radiometry versus osteometry in sex assessment: a study of the Cretan radius

Sex estimation is vital for biological profiling, thus qualitative and quantitative methods have been developed for every skeletal part in humans. However, somehow the radius has been neglected. This study aims to develop a sex estimation method on radiographs of the radius applicable in situations when classical osteometry cannot be applied. A total of 103 left radii were used in this study. Three classical measurements (maximum length, head diameter and distal breadth) were taken on the dry bones. Digital radiographs of the same radii were taken using a portable X-ray machine (Technix TCA 4R PLUS). Eight landmarks are selected on the radiograph of the proximal and six on the radiograph of the distal radius, generating in total 43 linear distances. ANOVA detected three osteometric and 24 radiometric variables that differed significantly between males and females (p<0.05). Classical osteometry resulted in up to 91% classification accuracy while the best multivariate formula of the radiometric method gave 88% correct classification. The study proposes a rapid and inexpensive alternative method for sex screening based on digital radiographs of the radius, a method that could be particularly advantageous in cases of mass disasters with numerous mutilated and/or burnt bodies where maceration is not an option.

Rare earth mineral potential in the southeastern U.S. Coastal Plain from integrated geophysical, geochemical, and geological approaches

We combined geophysical, geochemical, mineralogical, and geological data to evaluate the regional presence of rare earth element (REE)−bearing minerals in heavy mineral sand deposits of the southeastern U.S. Coastal Plain. We also analyzed regional differences in these data to determine probable sedimentary provenance. Analyses of heavy mineral separates covering the region show strong correlations between thorium, monazite, and xenotime, suggesting that radiometric equivalent thorium (eTh) can be used as a geophysical proxy for those REE-bearing minerals. Airborne radiometric data collected during the National Uranium Resource Evaluation (NURE) program cover the southeastern United States with line spacing varying from ∼2 to 10 km. These data show eTh highs over Cretaceous and Tertiary Coastal Plain sediments from the Cape Fear arch in North Carolina to eastern Alabama; these highs decrease with distance from the Piedmont. Quaternary sediments along the modern coasts show weaker eTh anomalies, except near coast-parallel ridges from South Carolina to northern Florida. Prominent eTh anomalies are also observed over large riverbeds and their floodplains, even north of the Cape Fear arch where surrounding areas are relatively low. These variations were verified using ground geophysical measurements and sample analyses, indicating that radiometric methods are a useful exploration tool at varying scales. Further analyses of heavy mineral separates showed regional differences, not only in concentrations of monazite, but also of rutile and staurolite, and in magnetic susceptibility. The combined properties suggest the presence of subregions where heavy mineral sediments are primarily sourced from high-grade metamorphic, low-grade metamorphic, or igneous terrains, or where they represent a mixing of these sources. Comparisons between interpreted sources of heavy mineral sands near the Fall Line and igneous and metamorphic Piedmont and Blue Ridge units showed a strong correspondence with rocks closest to the Fall Line and poor correspondence with rocks farther inland. This strongly suggests that the primary source of those heavy minerals, especially monazite, is the rocks that formed the rocky coast that was present during opening of the Atlantic Ocean, which in turn indicates the importance of coastal processes in forming heavy mineral sand concentrations. Furthermore, narrow radiometric eTh and K anomalies are associated with major rivers, indicating limited spatial influence of fluvial processes. Later coastal plain sediment deposition appears to have involved reworking of sediments, providing an “inheritance” of the rocky coast composition that persists for some distance from the Fall Line. However, this inheritance is reduced with distance, and sediments within ∼100 km of the coast in Georgia and Florida exhibit properties indicative of mixing from multiple sources.

A Mixed Radiometric Normalization Method for Mosaicking of High-Resolution Satellite Imagery

A new mixed radiometric normalization (MRN) method is introduced in this paper which aims to eliminate the radiometric difference in image mosaicking. The radiometric normalization methods can be classified as the absolute and relative approaches in traditional solutions. Though the absolute methods could get the precise surface reflectance values of the images, rigorous conditions required for them are usually difficult to obtain, which makes the absolute methods impractical in many cases. The relative methods, which are simple and practicable, are more widely applied. However, the standard for designating the reference image needed for these methods is not unified. Moreover, the color error propagation and the two-body problems are common obstacles for the relative methods. The proposed MRN approach combines absolute and relative radiometric normalization methods, by which the advantages of both can be fully used and the limitations can be effectively avoided. First, suitable image after absolute radiometric calibration is selected as the reference image. Then, the invariant feature probability between the pixels of the target image and that of the reference image is obtained. Afterward, an adaptive local approach is adopted to obtain a suitable linear regression model for each block. Finally, a bilinear interpolation method is employed to obtain the radiometric calibration parameters for each pixel. Moreover, the CIELAB color space is adopted to evaluate the results quantitatively. Experimental results of ZY-3, GF-1, and GF-2 data indicate that the proposed method can eliminate the radiometric differences between images from the same or even different sensors.

Combined Optimization of Feature Reduction and Classification for Radiometric Identification

Recently, dimensionality reduction for radiometric identification has attracted more attention. Previous research works generally considered dimensionality reduction and radio fingerprint classification separately, which resulted in poor performance. The reason is that the feature set after dimensionality reductions may not be suitable for classifier. In this letter, a new radiometric identification method based on combined optimization of dimensionality reduction and fingerprint classification is presented. The proposed method attempts to find an optimal dimension-reducing projection matrix by minimizing the classification error and maximizing the quadratic mutual information between the reduced low-dimensional features and the class label simultaneously. Since both the uncertainty of the true class label of the reduced low-dimensional features and the classification error of the classifier are considered, the proposed method can obtain better results in radiometric identification applications. Experiments on real data sets demonstrate that the proposed method not only outperforms the other methods with a higher accuracy of radiometric identification, but also has a better robustness against noises. The experimental results indicate that the proposed method can identify six emitters made by three different manufacturers with the classification accuracy over 95.08%.

A TWO-STEPS RADIOMETRIC CORRECTION OF SPOT-4 MULTISPECTRAL AND MULTITEMPORAL FOR SEAMLESS MOSAIC IN CENTRAL KALIMANTAN

This research analyzed the radiometric correction method using SPOT-4 imageries to produce the same reflectance for the same land cover. Top of Atmosphere (TOA) method was applied in previous radiometric correction approach, this TOA approach was upgraded with the reflectance effect from difference satellite viewing angle. The 250 scene of Central Kalimantan SPOT-4 imageries from 2006 until 2012 with varies viewing angle was used. This research applied two-step approaches, the first step is TOA correction, and the second step is normalization using a linear function of reflectance and satellite viewing angle. Gain and offset coefficient of this linear function was calculated using an iterative approach to producing the same reflectance in the forest area. The target of iterative processed is to minimize the standard deviation of a digital number from a forest area in the selected region. The result shows that the standard deviation of a digital number from a forest area in the two steps approach are 8.6, 16.5, and 16.8 for band 1, band 3 and band 4. These values are smaller compared with the standard deviation of digital number result from TOA approach are 15.0, 28,3 and 34.7 for band 1, band 3 and band 4. Decreasing the standard deviation shows the homogeneity of forest reflectance that could be seen in the seamless result. This algorithm can be applied for making seamless SPOT-4 mosaic whole of Indonesia.

A synthesis of tritium-labeled juvenile hormone and radiometric analysis of the enzymatic hydrolysis level

A method of insect juvenile hormone III (JH-III) labeling by thermally activated tritium was developed. Purification of the labeled compound was performed on a TLC silica gel plate using a system of hexane-ethyl acetate 2: 1. The molar radioactivity of [3H]JH-III was 2.2 Ci mmol–1. It was shown that tritium-labeled juvenile hormone can be used in the radiometric method for quantitative measurement of the activity of specific enzymes that hydrolyze juvenile hormone.

Development of a new radioanalytical technique for the determination of manganese(II) using potassium periodate

A radiometric method based on redox substoichiometry was applied to accurate and precise determination of manganese. The proposed technique is based on the substoichiometric oxidation of bivalent manganese to permanganate ions with potassium periodate, followed by isolation of the oxidized species by the extraction with tri-n-octylamine in chloroform. The method was successfully applied to the estimation of manganese content of various certified ores and alloys.

Measurement of the timing behaviour of off-the-shelf cameras

This paper presents a measurement method suitable for investigating the timing properties of cameras. A single light source illuminates the camera detector starting with a varying defined delay after the camera trigger. Pixels from the recorded camera frames are summed up and normalised, and the resulting function is indicative of the overlap between illumination and exposure. This allows one to infer the trigger delay and the exposure time with sub-microsecond accuracy. The method is therefore of interest when off-the-shelf cameras are used in reactive systems or synchronised with other cameras. It can supplement radiometric and geometric calibration methods for cameras in scientific use. A closer look at the measurement results reveals deviations from the ideal camera behaviour of constant sensitivity limited to the exposure interval. One of the industrial cameras investigated retains a small sensitivity long after the end of the nominal exposure interval. All three investigated cameras show non-linear variations of sensitivity at to during exposure. Due to its sign, the latter effect cannot be described by a sensitivity function depending on the time after triggering, but represents non-linear pixel characteristics.