Reflectance In Visible Wavelengths Research Articles

Water Turbidity Determination by a Satellite Imagery-Based Mathematical Equation for the Chao Phraya River

Turbidity is a standard water quality parameter that indicates its optical property in scattering light along the column containing suspended particles. The satellite imagery information of Sentinel-2 and the Chao Phraya River turbidity data from December 2016 to February 2021 was applied to develop a mathematical equation for turbidity determination. This practical and straightforward approach eliminates some constraints of traditional laboratory analysis, which is labour-intensive and time-consuming in monitoring the entire river. Four studied steps were implemented: data pre-processing, correlating analysis of numerical turbidity and satellite image reflectance, developing the mathematic equations for turbidity estimation, and its validation of use. Four different bands (B2, B3, B4, and B8) and three selection methods were investigated; single-band, combination band, and ratio band. The obtained results depicted that the reflectance of B4 in the single-band process promoted the highest correlation with turbidity compared to the others. The reflectance in visible wavelengths increased when the turbidity of river water increased, particularly B4. The mathematical power equation was a more suitable function for evaluating turbidity than linear regression, quadratic, and exponential functions. A similar concentration was obtained for measured and estimated turbidity in the validation. This finding demonstrated the potential application of remotely sensed data to estimate river water turbidity with high capability and accuracy that adequately supports spatial data continuity acquisition.

Age Determination of Blood-Stained Fingerprints Using Visible Wavelength Reflectance Hyperspectral Imaging

The ability to establish the exact time a crime was committed is one of the fundamental aims of forensic science. The analysis of recovered evidence can provide information to assist in age determination, such as blood, which is one of the most commonly encountered types of biological evidence and the most common fingerprint contaminant. There are currently no accepted methods to establish the age of a blood-stained fingerprint, so progress in this area would be of considerable benefit for forensic investigations. A novel application of visible wavelength reflectance, hyperspectral imaging (HSI), is used for the detection and age determination of blood-stained fingerprints on white ceramic tiles. Both identification and age determination are based on the unique visible absorption spectrum of haemoglobin between 400 and 680 nm and the presence of the Soret peak at 415 nm. In this study, blood-stained fingerprints were aged over 30 days and analysed using HSI. False colour aging scales were produced from a 30-day scale and a 24 h scale, allowing for a clear visual method for age estimations for deposited blood-stained fingerprints. Nine blood-stained fingerprints of varying ages deposited on one white ceramic tile were easily distinguishable using the 30-day false colour scale.

Comparison of Aerosol Reflectance Correction Schemes Using Two Near-Infrared Wavelengths for Ocean Color Data Processing

This paper reanalyzes the aerosol reflectance correction schemes employed by major ocean color missions. The utilization of two near-infrared (NIR) bands to estimate aerosol reflectance in visible wavelengths has been widely adopted, for example by SeaWiFS/MODIS/VIIRS (GW1994), OCTS/GLI/SGLI (F1998), MERIS/OLCI (AM1999), and GOCI/GOCI-II (A2016). The F1998, AM1999, and A2016 schemes were developed based on GW1994; however, they are implemented differently in terms of aerosol model selection and weighting factor computation. The F1998 scheme determines the contribution of the most appropriate aerosol models in the aerosol optical thickness domain, whereas the GW1994 scheme focuses on single-scattering reflectance. The AM1999 and A2016 schemes both directly resolve the multiple scattering domain contribution. However, A2016 also considers the spectrally dependent weighting factor, whereas AM1999 calculates the spectrally invariant weighting factor. Additionally, ocean color measurements on a geostationary platform, such as GOCI, require more accurate aerosol correction schemes because the measurements are made over a large range of solar zenith angles which causes diurnal instabilities in the atmospheric correction. Herein, the four correction schemes were tested with simulated top-of-atmosphere radiances generated by radiative transfer simulations for three aerosol models. For comparison, look-up tables and test data were generated using the same radiative transfer simulation code. All schemes showed acceptable accuracy, with less than 10% median error in water reflectance retrieval at 443 nm. Notably, the accuracy of the A2016 scheme was similar among different aerosol models, whereas the other schemes tended to provide better accuracy with coarse aerosol models than the fine aerosol models.

Mineralogy and chemistry of Ti-bearing lunar soils: Effects on reflectance spectra and remote sensing observations

This paper presents results of coordinated ultraviolet and visible wavelength reflectance measurements, X-ray diffraction analyses of mineral components, and micro X-ray fluorescence analyses of Ti concentrations of 13 lunar soil samples (<210 µm) that span a range of maturity and TiO2 contents. Results of these analyses are used to determine the effects of soil maturity, TiO2 concentration, and specific mineralogical makeup, especially ilmenite content, on the ultraviolet/visible (UV/VIS) ratio for application to remote sensing observations of the Moon and other airless bodies. We find that measured ilmenite weight percent correlates highly with measured TiO2 concentrations. Thus, the ilmenite content is a good predictor of TiO2 concentration. Ilmenite is the main contributor of TiO2 for soils with greater than about 2 wt.% TiO2, so we take the effects of TiO2 on reflectance spectra to be essentially those of ilmenite. Constraining the data set to eight mature Apollo soils, we find that among the UV/VIS ratios from laboratory-measured spectra, the 321/415 nm ratio shows the best correlation with TiO2 and ilmenite. Moreover, for soils with similar maturity in the submature to mature range, those with higher TiO2 have higher 321/415 UV/VIS ratios. Finally, the correlation between TiO2 content and 321/415 ratio in samples measured in the lab appears weaker than for the same relationship using the Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) spectral data for the 321/415 ratio of Apollo ground-truth sites. The correlation between lab-derived 321/415 ratios and TiO2 content for measured samples improves when low-maturity samples are excluded from the dataset, implying that the LROC WAC spectra at 400 m/pix spatial resolution senses mostly mature soil.

Impact of impurities and cryoconite on the optical properties of the Morteratsch Glacier (Swiss Alps)

Abstract. The amount of reflected energy by snow and ice plays a fundamental role in their melting processes. Different non-ice materials (carbonaceous particles, mineral dust (MD), microorganisms, algae, etc.) can decrease the reflectance of snow and ice promoting the melt. The object of this paper is to assess the capability of field and satellite (EO-1 Hyperion) hyperspectral data to characterize the impact of light-absorbing impurities (LAIs) on the surface reflectance of ice and snow of the Vadret da Morteratsch, a large valley glacier in the Swiss Alps. The spatial distribution of both narrow-band and broad-band indices derived from Hyperion was analyzed in relation to ice and snow impurities. In situ and laboratory reflectance spectra were acquired to characterize the optical properties of ice and cryoconite samples. The concentrations of elemental carbon (EC), organic carbon (OC) and levoglucosan were also determined to characterize the impurities found in cryoconite. Multi-wavelength absorbance spectra were measured to compare the optical properties of cryoconite samples and local moraine sediments. In situ reflectance spectra showed that the presence of impurities reduced ice reflectance in visible wavelengths by 80–90 %. Satellite data also showed the outcropping of dust during the melting season in the upper parts of the glacier, revealing that seasonal input of atmospheric dust can decrease the reflectance also in the accumulation zone of the glacier. The presence of EC and OC in cryoconite samples suggests a relevant role of carbonaceous and organic material in the darkening of the ablation zone. This darkening effect is added to that caused by fine debris from lateral moraines, which is assumed to represent a large fraction of cryoconite. Possible input of anthropogenic activity cannot be excluded and further research is needed to assess the role of human activities in the darkening process of glaciers observed in recent years.

The non-contact detection and identification of blood stained fingerprints using visible wavelength hyperspectral imaging: Part II effectiveness on a range of substrates

Biological samples, such as blood, are regularly encountered at violent crime scenes and successful identification is critical for criminal investigations. Blood is one of the most commonly encountered fingerprint contaminants and current identification methods involve presumptive tests or wet chemical enhancement. These are destructive however; can affect subsequent DNA sampling; and do not confirm the presence of blood, meaning they are susceptible to false positives.A novel application of visible wavelength reflectance hyperspectral imaging (HSI) has been used for the non-contact, non-destructive detection and identification of blood stained fingerprints across a range of coloured substrates of varying porosities. The identification of blood was based on the Soret γ band absorption of haemoglobin between 400nm and 500nm.Ridge detail was successfully visualised to the third depletion across light coloured substrates and the stain detected to the tenth depletion on both porous and non-porous substrates. A higher resolution setup for blood stained fingerprints on black tiles, detected ridge detail to the third depletion and the stain to the tenth depletion, demonstrating considerable advancements from previous work. Diluted blood stains at 1500 and 1000 fold dilutions for wet and dry stains respectively were also detected on pig skin as a replica for human skin.

The non-contact detection and identification of blood stained fingerprints using visible wavelength reflectance hyperspectral imaging: Part 1

Blood is one of the most commonly encountered types of biological evidence found at scenes of violent crime and one of the most commonly observed fingerprint contaminants. Current visualisation methods rely on presumptive tests or chemical enhancement methods. Although these can successfully visualise ridge detail, they are destructive, do not confirm the presence of blood and can have a negative impact on DNA sampling.A novel application of visible wavelength reflectance hyperspectral imaging (HSI) has been used for the detection and positive identification of blood stained fingerprints in a non-contact and non-destructive manner on white ceramic tiles. The identification of blood was based on the unique visible absorption spectrum of haemoglobin between 400 and 500nm.HSI has been used to successfully visualise ridge detail in blood stained fingerprints to the ninth depletion. Ridge detail was still detectable with diluted blood to 20-fold dilutions. Latent blood stains were detectable to 15,000-fold dilutions. Ridge detail was detectable for fingerprints up to 6months old. HSI was also able to conclusively distinguish blood stained fingerprints from fingerprints in six paints and eleven other red/brown media with zero false positives.

A comparison of visible wavelength reflectance hyperspectral imaging and Acid Black 1 for the detection and identification of blood stained fingerprints

Bloodstains are often encountered at scenes of violent crime and have significant forensic value for criminal investigations.Blood is one of the most commonly encountered types of biological evidence and is the most commonly observed fingerprint contaminant. Presumptive tests are used to test blood stain and blood stained fingerprints are targeted with chemical enhancement methods, such as acid stains, including Acid Black 1, Acid Violet 17 or Acid Yellow 7. Although these techniques successfully visualise ridge detail, they are destructive, do not confirm the presence of blood and can have a negative impact on DNA sampling.A novel application of visible wavelength hyperspectral imaging (HSI) is used for the non-contact, non-destructive detection and identification of blood stained fingerprints on white tiles both before and after wet chemical enhancement using Acid Black 1. The identification was obtained in a non-contact and non-destructive manner, based on the unique visible absorption spectrum of haemoglobin between 400 and 500nm. Results from the exploration of the selectivity of the setup to detect blood against ten other non-blood protein contaminants are also presented. A direct comparison of the effectiveness of HSI with chemical enhancement using Acid Black 1 on white tiles is also shown.

Current Status of Hyperspectral Data Processing Techniques for Monitoring Coastal Waters

In this study, we introduce various hyperspectral data processing techniques for the 2014년 10월 28일 접수 Received on October 28, 2014 / 2014년 12월 26일 수정 Revised on December 26, 2014 / 2015년 1월 26일 심사완료 Accepted on January 26, 2015 1 한국해양과학기술원 해양위성연구센터 Korea Ocean Satellite Research Center, Korea Institute of Ocean Science and Technology 2 한국해양대학교 해양과학기술전문대학원 OST-School, Korea Maritime and Ocean University 3 과학기술연합대학원대학교 해양환경시스템과학과 Dept. of Marine Environmental System Science, Korea University of Science and Technology(UST) ※ Corresponding Author E-mail : yangsc@kiost.ac 연안해역 모니터링을 위한 초분광영상 처리기법 현황 / 김선화· 양찬수 49 monitoring of shallow and coastal waters to enlarge the application range and to improve the accuracy of the end results in Korea. Unlike land, more accurate atmospheric correction is needed in coastal region showing relatively low reflectance in visible wavelengths. Sun-glint which occurs due to a geometry of sun-sea surface-sensor is another issue for the data processing in the ocean application of hyperspectal imagery. After the preprocessing of the hyperspectral data, a semi-analytical algorithm based on a radiative transfer model and a spectral library can be used for bathymetry mapping in coastal area, type classification and status monitoring of benthos or substrate classification. In general, semi-analytical algorithms using spectral information obtained from hyperspectral imagey shows higher accuracy than an empirical method using multispectral data. The water depth and quality are constraint factors in the ocean application of optical data. Although a radiative transfer model suggests the theoretical limit of about 25m in depth for bathymetry and bottom classification, hyperspectral data have been used practically at depths of up to 10 m in shallow and coastal waters. It means we have to focus on the maximum depth of water and water quality conditions that affect the coastal applicability of hyperspectral data, and to define the spectral library of coastal waters to classify the types of benthos and substrates.

Spectral reflectance of floodplain vegetation communities of the Okavango Delta

Knowledge of wetland vegetation spectral reflectance signatures can assist in spectral classification of remotely sensed images for monitoring of wetland hydroperiod. This study aimed at assessing the differences between wetland vegetation communities of varying species composition and density in terms of spectral reflectance. The investigation was carried out in floodplains at Nxaraga and Seronga in the Okavango Delta, Botswana. Spectral measurements were conducted during rising and receding flood stages. In each study area, 2 transects were located in homogeneous macrophyte stands, and in each transect 5–10 1 m2 quadrats were randomly set. In each quadrat, water depth and cover percentages (green leaved and senescent) of macrophyte vegetation were recorded, and a full reflectance spectrum between 325 and 1,075 nm wavelengths captured using a handheld spectroradiometer. Multiple regression analysis with stepwise selection of significant variables based on AIC was performed to determine the influence of various stand characteristics on spectral reflectance and vegetation indices (NDVI and EVI). The results showed that stand characteristics explained a large proportion of variance in spectral vegetation indices with r2 = 0.67 for NDVI and r2 = 0.75 for EVI. For NDVI, the significant explanatory variables were percentage green cover, senescent cover and water depth, while for EVI it was the total vegetation cover. Analysis of regression residuals for the various vegetation community classes showed significant differences between the classes in their NDVI, but no differences in EVI, with the exception of the Panicum repens class. Reflectance in visible wavelengths did not vary significantly between sites and seasons, but the NIR reflectance differed across sites and seasons. The results indicate that the simple vegetation indices in the Okavango Delta respond strongly to stand characteristics and thus can be used to derive these from remote sensing imagery. The scope for determination of vegetation communities from these indices is limited, however.

The application of visible wavelength reflectance hyperspectral imaging for the detection and identification of blood stains.

Current methods of detection and identification of blood stains rely largely on visual examination followed by presumptive tests such as Kastle-Meyer, Leuco-malachite green or luminol. Although these tests are useful, they can produce false positives and can also have a negative impact on subsequent DNA tests. A novel application of visible wavelength reflectance hyperspectral imaging has been used for the detection and positive identification of blood stains in a non contact and non destructive manner on a range of coloured substrates. The identification of blood staining was based on the unique visible absorption spectrum of haemoglobin between 400 and 500 nm. Images illustrating successful discrimination of blood stains from nine red substances are included. It has also been possible to distinguish between blood and approximately 40 other reddish stains. The technique was also successfully used to detect latent blood stains deposited on white filter paper at dilutions of up to 1 in 512 folds and on red tissue at dilutions of up to 1 in 32 folds. Finally, in a blind trial, the method successfully detected and identified a total of 9 blood stains on a red T-shirt.

Quantification of Absorber through a Scattering Medium of Different Thickness Using Evanescent Light Piping

A non-invasive method has been developed for analyte quantification in fluids surrounded by optically-scattering, opaque walls. This method is based on steady state, visible wavelength reflectance measurements made simultaneously at multiple positions on the surface of a sample. Previous work has shown that reflectance measurements contain information about underlying scattering layers in layered scattering samples. We hypothesise that similar information about an absorbing layer below a scattering layer can be obtained from evanescent wave effects. Principal component analysis showed the data to be composed of three components, which were refined by a multivariate curve resolution alternating least squares (MCR-ALS) approach with non-negativity constraints. The first component is related to the scattering layer thickness, the second is associated with analyte concentration and the third is due to a minor back reflection within the sample cell. Both MCR and stagewise multi-linear regression (SMLR) approaches were taken to estimate analyte concentration and scattering layer thickness, for samples having thicknesses between 1 mm and 8 mm. Results demonstrate that a simple experimental configuration can easily predict optical properties of unknown samples. With the adoption of a multi-wavelength approach to this method, it is expected that improved absorption coefficient (μa) estimation accuracy can be realised in a variety of application areas such as in analysis through opaque containers, in vivo measurements and in-line monitoring of reactions.

Temporal change in canopy reflectance at visible wavelength as a biophysical indicator of jute (Corchorus capsularis L.) growth

Changes in the reflectance and transmittance of jute canopy at different visible wavelengths of solar radiation are measured at different growth stages throughout the period of half crop cycle. The reflectance is found to gradually decrease and attain a steady value with canopy growth up to about one‐third of the crop cycle. As an independent study, vegetation growth parameters such as canopy height, leaf length, leaf area are simultaneously measured. It is concluded that although these parameters have individual properties, the whole canopy ultimately occupies a constant fraction of the air volume over the soil. As a combined effect of the above parameters, the transmittance through the leaf–air composite becomes saturated. A suitable mathematical explanation is given for the above. It is affirmed from these two independent sets of experiments that the vegetation growth is truly echoed in the temporal change in visible wavelength reflectance, the remotely sensible parameter. Thus the present work proposes a methodology for remotely observing the growth of vegetation and it is justified with jute, an important cash crop in eastern India.

Biochemical and reflectance variation throughout a Sitka spruce canopy

The reflectance properties of tree leaves and canopies are influenced by their biochemical concentration. Modelling and empirical studies have been used to better understand this relationship for the remote sensing of foliar biochemical concentration. The success of these studies have been predicated on two implicit assumptions; first, that variability in biochemical concentration and reflectance within any one canopy is small, and second, that foliar samples from a point (usually the top) of the canopy could be used to represent the canopy as a whole. To evaluate these two assumptions the three-dimensional variation of various biochemical and reflectance characteristics of a Sitka spruce canopy were examined. Biochemical concentrations varied with canopy depth and needle age: chlorophyll and cellulose concentrations increased slightly with canopy depth, water and lignin concentrations were greatest in the lower canopy, and nitrogen concentrations were similar throughout the canopy. Reflectance in visible wavelengths decreased with canopy depth, as did reflectance at the ‘red edge’. Biochemical concentration also varied with needle age: chlorophyll concentration increased with needle age; lignin and cellulose concentrations were similar for all ages of needles though variations in water and nitrogen concentration were more complex. Overall, however, these variations in biochemical concentrations were slight and it was concluded that foliage samples taken from near the top of the canopy and incorporating needles of a variety of ages would be representative of the canopy as a whole for the purposes of the remote sensing of foliar biochemical concentration. This paper also explores the strength of the relationships between biochemical concentration and reflectance and found them all to be weak, with the exception of those between chlorophyll concentration and reflectance.

Strong correlation between high-temperature electronic and low-temperature magnetic ordering inLa1−xCaxMnO3continuous phase diagram

Optical and microwave impedance and magnetic mapping of continuous phase diagram of thin film ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ was achieved on a single chip. The optical and microwave impedance images obtained by charge-coupled device camera and scanned evanescent microwave probe showed abrupt variations in visible wavelength reflectance and microwave impedance as functions of composition at room temperature. The low-temperature magnetic order probed by scanning superconducting quantum interference device microscope is directly correlated with the room-temperature electrical impedance variation. Most of these variations may arise from remnant electronic orbital ordering persisting to room temperature in these compounds. We also observed a narrow singular stripe in composition with dramatically increased conductivity.

Sea surface velocities in shallow seas extracted from sequential coastal zone color scanner satellite data

Sequential images of visible wavelength reflectance from channel 3 (540–560 nm) of the Coastal Zone Color Scanner (CZCS) have been used for computing advective velocities in the eastern English Channel, using the maximum cross‐correlation technique. The computation method, known as matched filtering, is widely used by meteorologists and has recently been applied by oceanographers to detect sea surface motion from satellite infrared images. Provided accurate coregistration of images is achieved by matching ground control points, significant correlation is obtained when the technique is applied to CZCS data, and coherent velocity distributions are obtained for United Kingdom shelf waters. The residual circulation patterns for the English Channel are found to be consistent with previous studies and recent observations.

Effect of dew on canopy reflectance and temperature

The diurnal behavior of canopy reflectance and emittance was characterized for six spring wheat cultivars using two ground-based radiometers that had spectral bandpass characteristics similar to the multispectral scanner and thematic mapper radiometers on Landsats 4 and 5. Nadir measurements of spectral reflectance and emittance were made over well-watered canopies with and without dew to determine its effect on each wavelength interval. The diurnal patterns of reflectances from canopies without dew were symmetric with respect to solar noon. However, when dew was present on canopies, morning reflectances in wavelengths shorter than 0.7 μm and longer than 1.15 μm were significantly different than those observed during the afternoon under similar solar zenith angles. Quantitative measurements of dew density in each cultivar established that moderately high dew levels increased reflectance in visible wavelengths by 40–60%, and decreased reflectance in wavelengths between 1.15 and 2.35 μm by 25–60%. No effect of dew was noted in the near-IR region of the spectrum between 0.7 and 1.1 μm or the thermal IR (10.4–12.5 μm).