Variations In Spectral Characteristics Research Articles

Gemological Characteristics of Blue-Violet Cordierite

Cordierite is a violet-blue gem mineral primarily composed of magnesium aluminum silicate. This study employed three samples of Mg-cordierite and conducted tests on their gemological characteristics, spectroscopic features, and chemical composition using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet spectrophotometry, X-ray photoelectron spectroscopy (XPS), and electron microprobe. The study also explored and analyzed the polychroism and coloration mechanisms of the samples. The results indicate that the lattice vibrations of the Mg-cordierite samples differ along the directions parallel to the a, b, and c crystallographic axes, leading to certain variations in spectral characteristics among these directions. The article provides experimental evidence for the reasons for the polychroism of cordierite in different crystal axes, which is of great significance in the quality evaluation of cordierite.

Variability in spectral absorption within cryptophyte phycobiliprotein types.

Cryptophytes are known to vary widely in coloration among species. These differences in color arise primarily from the presence of phycobiliprotein accessory pigments. There are nine defined cryptophyte phycobiliprotein (Cr-PBP) types, named for their wavelength of maximal absorbance. Because Cr-PBP type has traditionally been regarded as a categorical trait, there is a paucity of information about how spectral absorption characteristics of Cr-PBPs vary among species. We investigated variability in primary and secondary peak absorbance wavelengths and full width at half max (FWHM) values of spectra of Cr-PBPs extracted from 75 cryptophyte strains (55 species) grown under full spectrum irradiance. We show that there may be substantial differences in spectral shapes within Cr-PBP types, with Cr-Phycoerythrin (Cr-PE) 545 showing the greatest variability with two, possibly three, subtypes, while Cr-PE 566 spectra were the least variable, with only ±1 nm of variance around the mean absorbance maximum of 565 nm. We provide additional criteria for classification in cases where the wavelength of maximum absorbance alone is not definitive. Variations in spectral characteristics among strains containing the same presumed Cr-PBP type may indicate differing chromophore composition and/or the presence of more than one Cr-PBP in a single cryptophyte species.

Visible and Near-Infrared Hyperspectral Diurnal Variation Calibration for Corn Phenotyping Using Remote Sensing

Remote sensing coupled with hyperspectral technology has become increasingly popular to investigate plant traits, showcasing its advantages in studying plant growth, health, and productivity. The quality of the collected hyperspectral images is crucial for subsequent data analysis and plant phenotyping studies. However, diurnal variations in spectral characteristics introduce more data variance in canopy reflectance spectra, raising the cost of subsequent analyses and compromising the performance of trait estimation models. In this study, a fixed gantry platform in a cornfield was used to capture visible and near-infrared (VNIR) hyperspectral images of corn canopies at consecutive time intervals. By applying reference board calibration and locally weighted scatterplot smoothing to minimize the effects of ambient light and daily growth, diurnal spectral changes across all involved VNIR wavelengths were investigated. Several distinct diurnal patterns were observed to have close connections with the plants’ physiological effects. Diurnal calibration models were established at every wavelength by employing the least squares polynomial algorithm, with the highest coefficient of determination reaching 0.84. Moreover, by employing diurnal calibration in canopy spectra processing, the reduction in spectral variance brought about by varying imaging time was evidently exhibited. This study not only reveals the diurnal spectral variation pattern at VNIR bands but also offers a reliable, straightforward, and low-cost approach to improve the quality of remote sensing data and reduce the inherent variance brought about via the different imaging times ensuring that comparable spectral analysis can be performed under relatively fair conditions.

Pump power induced instability and hysteresis in an all-normal dispersion linear mode-locked fiber laser

In this manuscript, experimental studies on the instability and hysteresis in an all-normal dispersion (ANDi) fiber laser have been presented. The laser was mode-locked by using a semiconductor saturable absorber mirror and a chirped fiber Bragg grating in linear cavity configuration and under the stable conditions it delivered stationary dissipative soliton pulses with characteristic rectangular-shaped steep-edged spectrum. With increasing the pump power, the laser transits to a non-stationary state with a near trapezoidal-shaped spectrum with significant temporal instabilities. The hysteresis associated with the state transition and variations in spectral characteristics has been studied including dispersive Fourier transform based analysis. Pump power induced state transition in an ANDi linear cavity with a physical saturable absorber without the influence of any physical polarization controller or apparent limitation due to spectral filtering is the key observation presented in this paper.

Variation in Spectral Characteristics of Dissolved Organic Matter and Its Relationship with Phytoplankton of Eutrophic Shallow Lakes in Spring and Summer

The compositional characteristics of dissolved organic matter (DOM) have important implications for lake water quality and aquatic ecology. Seasonal changes of dissolved organic matter (DOM) as well as phytoplankton abundance and composition in Shahu Lake from April to July were characterized by three-dimensional fluorescence spectroscopy (3DEEMs) combined with parallel factor (PARAFAC) analysis. The relationship between the response of components of the DOM and phytoplankton abundance were explored via Pearson correlation and redundancy analysis (RDA) in the overlying water. The results showed that the DOM was composed mainly of tryptophan-like (C2+C4), fulvic-acid-like (C3), humic-acid-like (C1), and tyrosine-like (C5) compounds that accounted for 44.47%, 20.18%, 20.04%, and 15.31%, respectively, of the DOM. The DOM was derived from both endogenous and terrestrial sources. With seasonal changes, endogenous DOM produced by phytoplankton growth and metabolism gradually increased. In spring and summer (April–July), Chl-a concentrations were significantly correlated with C3 (p < 0.01) and C5 (p < 0.05). The concentration of protein-like fractions (C2+C4, C5) were correlated with Cyanobacteria abundance, and the concentrations of humic-like component content (C1, C3) were correlated with the abundance of Xanthophyta, Chlorophyta, and Cryptophytes. Overall, phytoplankton density and Chl-a content increased by 125% and 197%, respectively, and the abundance of C3 and C5 in the DOM increased by 7.7% and 22.15% in parallel. Thus, seasonal phytoplankton growth had an important influence on the composition of the DOM.

The impact of natural sunlight irradiation on the biotoxicities of different molecular sizes EfOM/SRNOM and its relationship with spectral and molecular level parameters

Natural sunlight irradiation is regarded as an efficient and low-carbon method for controlling the biotoxicity of effluents from domestic wastewater treatment plants (WWTPs). Dissolved organic matter in WWTPs effluent (EfOM) is responsible for the non-specific biotoxicity of effluent. In the present study, the variation in spectral characteristics, molecular composition, luminescent bacteria toxicity, and genotoxicity of EfOM of different molecular sizes (MOSs) during natural sunlight irradiation were investigated from a systematic perspective, and the standard natural organic matter from the Suwannee River (SRNOM) was synchronously assessed for comparative purposes. To further explore the cause of the biotoxicity changes, the relationships between the spectral or molecular level parameters (obtained from FT-ICR MS analysis) and biotoxicity were assessed using correlation analysis. The molecules in <1 kDa EfOM with lower molecular weight, higher unsaturation degree, and higher humification and fluorescence had higher luminescent bacteria toxicity under sunlight irradiation. However, in the <1 kDa SRNOM, the molecules which were characterized by higher humification and fluorescence had higher luminescent bacteria toxicity. The notable genotoxicity reduction of EfOM under sunlight irradiation was attributed to the photochemical degradation of components with a high unsaturation degree. Such findings could enable ecological safety improvement of aquatic environments using natural sunlight.

Variation in spectral characteristics of dissolved organic matter derived from rape straw of plants grown in Se-amended soil

Straw return is an effective management practice. It not only utilizes agricultural waste but also introduces dissolved organic matter (DOM) into the soil. Selenium (Se) is an essential trace element in the human diet and contributes to the popularity of Se-enriched agricultural products in the Chinese market. Moreover, there are still some Se-enriched agricultural products that have yet to be utilized. This study investigated whether Se addition in soil caused component changes in the DOM extracted from rape straw. DOM extracted from rape straw grown in soil with four Se levels (0, 0.1, 0.5 and 1.0 mg Se kg−1 soil) was characterized by UV-Visible spectroscopy, fluorescence spectroscopy and FTIR spectroscopy. The UV-visible spectra revealed that 0.1 mg Se kg−1 soil reduced the molecular weight of DOM and caused the presence of more irreplaceable aromatic structures in the substituent groups of the DOM, while 0.5 and 1.0 mg Se kg−1 soil only reduced the DOM molecular weight. Fluorescence spectroscopy indicated that Se improved the humification degree but reduced the aromaticity of DOM. FTIR spectra proved that Se altered the contents of carboxylic acids, amino acids, alcohols and aromatic heterocycles in DOM, which were maximized in the 0.5 and 1.0 mg Se kg−1 treatment groups. We concluded that Se application could change the composition of DOM extracted from rape straw, potentially impacting the nutrient bioavailability in soil. This study provides basic data on Se-enriched rape straw utilization for eco-agriculture.

Modelling the Spectral Uncertainty of Geographic Features in High-Resolution Remote Sensing Images: Semi-Supervising and Weighted Interval Type-2 Fuzzy C-Means Clustering

The spectral uncertainty refers to the diversity and variations of spectral characteristics within a single geographic object or across different objects of the same class. Usually, existing methods represent the spectral characteristics as precise single-valued curves. Thus, the spectral variations cannot be modeled, which further restricts the analysis and classification performance of remote sensing images. On the other hand, unsupervised methods have poor performance in classification and modeling uncertainty, while supervised methods need a large number of samples with high quality. Fuzzy semi-supervised clustering (FSSC) methods achieve a high accuracy with limited labelled samples. Thus, currently, FSSC methods attract more and more attention. This paper proposes a novel method to model the spectral uncertainty for very-high-resolution (VHR) images based on interval type-2 fuzzy sets (IT2 FSs), namely the hierarchical semi-supervising and weighted interval type-2 fuzzy c-means for objects (hierarchical SSW-IT2FCM-O) clustering method. In this method, the VHR image is segmented into image objects to reduce spectral uncertainty within objects. Spectral values, spectral indices and textures were weighted for object-based image classification. To further reduce spectral uncertainty across different objects of the same class, the spectral characteristics of land cover types were represented as banded curves with certain widths instead of precise single-valued spectral curves. The experimental results show that the banded spectral curves produced by the hierarchical SSW-IT2FCM-O can effectively model the spectral uncertainty of geographic objects. From the perspective of classification, four typical validity indices along with the confusion matrix and kappa coefficient were used to test the effectiveness of the hierarchical SSW-IT2FCM-O method, and these indices show that the presented method SSW-IT2FCM-O has greater classification accuracy than the existing FSSC methods and, more importantly, it requires smaller training samples than the existing methods.

Variation in spectral characteristics of dissolved organic matter in inland rivers in various trophic states, and their relationship with phytoplankton

Dissolved organic matter (DOM) plays an important role in aquatic ecosystems. This study aimed to reveal the variation in spectral characteristics of DOM in inland rivers in various trophic states, and understand the relationship between spectral characteristics of DOM and phytoplankton composition in various trophic states. Our investigation was carried out on the Weihe River in Shaanxi Province, China. Three humic-like substances and one protein-like substance were identified from the DOM by examination of three-dimensional (3D) fluorescence combined with parallel factor (PARAFAC) analysis and UV–Vis spectroscopy. The trophic states in this study area ranged from mesotrophic to hyper-eutrophic (37 < Trophic States Index (TSI) < 76). As the trophic states increased, the amount of phytoplankton rose, and the dominant phylum gradually changed from bacillariophyta to cyanophyta and chlorophyta. The UVA humic-like substance C1 (λEx/Em = 250(310)/400 nm) and the protein-like substance C4 (λEx/Em = 240(280)/338), frequently found in pure cultures of various phytoplankton species, were considered to be phytoplankton secretions. As the trophic state increased, the fluorescence intensity of C1 and C4 increased, along with the rising phytoplankton biomass. The UVC humic-like substance C2 (λEx/Em = 260/480 nm), derived from a terrestrial source, did not change significantly along with the increasing trophic state. The humic-like substance C3 (λEx/Em = 270/430 nm), produced by microbial decomposition, increased significantly in individual places as the trophic state increased. We concluded that the trophic state can increase the endogenous proportion of DOM by promoting phytoplankton growth, but that the changes in phytoplankton community affected by trophic state have no direct influence on the spectral characteristics of DOM.

Optical emission spectroscopy study on flashover along insulator surface due to particle contamination

AbstractThe surface flashover behavior in ambient air and nitrogen are studied at a pressure of 1 kg/cm2 using optical emission spectroscopy. A high dc voltage is applied to Rogowski profile electrodes with polyoxymethylene as the insulator between the electrodes. Three different conditions of needle protrusion along the surface of polyoxymethylene are used to study the variation in spectral characteristics due to particle contamination. When the insulator is placed between the spark gap electrodes, the OES spectra are dominated by the Hα line in air and nitrogen medium. It was found that the intensity of N2+ (B-X) emission is less in air surrounding the insulator medium. The plasma temperature during bulk breakdown in air is 0.433 eV, which increases to 0.434 eV with the pressurized nitrogen, which further increases in the presence of insulator to 0.441 eV and 0.44 eV in nitrogen and air, respectively. The electron density is obtained from the N emission line at 746.8 nm and the estimated peak value is 2.85 × 1012 cm−3 in the presence of insulator. The plasma temperature decreases with increase in distance of particle contamination from cathode. The increase in electron density in air, as compared to nitrogen implies more material desorption in air which is also supported by the comparisons of Hα lines.

Methods of IR spectroscopy in monitoring of chemotherapy of oncological pathologies using palladium complexes

FTIR spectroscopy is used to study mammary-gland tissues of mice with a sarcoma tumor (strain 180). Spectral features that are typical of malignant tumors are revealed in the FTIR spectra in the sarcoma-tumor tissues. Tumor tissues are studied after treatment using coordination compounds based on palladium complexes with 3-amino-1-hydroxypropylidene-1,1-diphosphonic acid and zoledronic acid. A therapeutic effect is not revealed after treatment using palladium complex with 3-amino-1-hydroxypropylidene-1,1-diphosphonic acid. The suppression of tumor growth amounts to 59% when palladium complexes with zoledronic acid are used. Suppression of tumor growth is accompanied by variations in spectral characteristics. With respect to diagnostic features, the FTIR spectra of tumor tissues after treatment with the palladium complexes with zoledronic acid are similar to the FTIR spectra of tissues that are free of malignant tumors. Specific spectroscopic characteristics that make it possible to control the chemotherapy of oncological pathologies are determined.

Mossbauer parameters of iron in sulfate minerals

Although Fe-sulfate minerals occur only rarely on Earth as alteration products of sulfidic basalts or in hydrothermal systems, multiple lines of evidence point to the importance of Fe- (and other) sulfate minerals on the surface of Mars. One such martian data set comes from the MIMOS II Mössbauer spectrometers on the Mars Exploration Rovers, which acquired hundreds of spectra from the martian surface at two locations. Interpretation of those spectra has been limited by the lack of a comprehensive set of laboratory analog spectra of the broad range of naturally occurring sulfate minerals. Accordingly, this study reports Mössbauer data of 98 samples representing 47 different sulfate mineral species, all containing six- or higher-coordinated Fe. The resultant Mössbauer parameters are related to the local polyhedral environment around the Fe cation in each mineral to explain variations in spectral characteristics. Results show that the size of the coordination polyhedron is the best predictor of quadrupole splitting, which increases with both octahedral volume and mean bond length. Species within groups of structurally similar minerals are shown to have comparable spectral peaks that generally fall within small ranges. Although coordination polyhedron geometry is not necessarily unique to any particular mineral species or group, Mössbauer data can be used to help constrain mineral identifications from martian spectra. The number of mineral species is large, but the range of crystal structures and hyperfine parameters may be small, so that in many cases, individual minerals cannot be uniquely fingerprinted. Examples would include quenstedtite, coquimbite, kornelite, and lausenite, which have indistinguishable spectra, as do apjohnite, bilinite, dietrichite, and römerite. Overlap of Mössbauer parameters is a particular complication for identification of Fe 3+ -rich phases because the range of Mössbauer parameters for Fe3+ in any coordination number is so small. Previous analyses of martian Mössbauer spectra reported the presence of jarosite (Klingelhöfer et al. 2004; Morris et al. 2004) and an unspecific ferric sulfate (Morris et al. 2008). New data presented here indicate that botryogen, metasideronatrite, and slavikite exhibit Mössbauer spectra similar to those attributed to jarosite at Meridiani Planum. Fibroferrite and rhomboclase have parameters similar to those observed at Arad Samra, and copiapite and parabutlerite could be present at Tyrone Mount Darwin and Berkner Island. Unique mineral identifications are generally not possible from Mössbauer data alone, particularly for paramagnetic phases, although combining Mössbauer results with other data sets enables a greater level of confidence in constraining mineralogy. This study provides a new expansive data set for future interpretation of iron sulfates on Mars

Quantification and comparison of spectral characteristics of sensors on board Resourcesat-1 and Resourcesat-2 satellites

This letter presents quantification and comparison of spectral characteristics of three similar sensors, namely Linear Imaging Self-Scanning Sensor (LISS)-III, LISS-IV and Advanced Wide Field Sensor (AWiFS) on board Indian Remote Sensing (IRS) satellites Resourcesat-1 (RS1) and Resourcesat-2 (RS2). Theoretical estimates of three critical spectral characteristics, effective bandwidth (Δλ), central wavelength (λc) and bandpass solar exoatmospheric irradiance (E 0), have been computed based on the laboratory measurements of the relative spectral response (RSR) for each spectral band. A comparative analysis between two estimates computed through the moment method and the full width at half maximum (FWHM) method showed noticeable differences of the order of 4.4–14.1 nm in Δλ and λc for the corresponding band of Resourcesat sensors. A coefficient of variation (CV) of the order of 0.1–1.3% was noticed in E 0 among various Resourcesat sensors, which could induce a difference of 0.26–3.27% in the estimation of top-of-atmosphere (TOA) reflectance. The variations in spectral characteristics among the Resourcesat sensors should be taken into account when comparisons are made between measurements from sensors on board RS1 and RS2 satellites, for example, for long-term monitoring of the Earth's environment.

Three-date landsat thematic mapper composite in seasonal land-cover change identification in a mid-latitudinal region of diverse climate and land use

Land-use and land-cover (LULC) classification accuracy in different seasons is not constant due to seasonal variations in spectral characteristics of different land-cover classes. This study addresses the problem of selecting a suitable season for mapping land-cover and identifying changes between seasons of midlatitude (29 deg 30′ to 31 deg 0′S) region of distinctive summer and winter rainfall, a broad altitudinal range, a temperate to subtropical climate and diverse land uses (e.g., summer and winter crops and nature conservation). Six landsat thematic mapper (TM) images from 2007 to 2009 were used taking three sequential three-date composites for seasonal change detection. January (midsummer) was the most suitable season in providing high spectral separability between most classes. The study demonstrates the means for improving LULC classification accuracy through the selection of optimal season for individual LULC class mapping and also provides a method of combining two or more classifications using referential refinement technique to generate aggregate LULC map of the region.

Wavelet analysis of the m. vastus lateralis surface electromyogram activity in incremental tests until exhaustion using bicycle and knee extension exercises

Continuous wavelet analysis was used to study the spectral characteristics of the m. vastus lateralis electromyographic activity in two I : rhythmic knee-joint extensions and cycling. Wavelet analysis of surface electromyograms (EMGs) recorded during cyclic contractions of the same muscle during the two types of movements showed differences in the pattern of changes in the timefrequency characteristics of the signal during a single cycle of movements with different loads, as well as differences in the slow variations of spectral characteristics related to the development of muscle fatigue during the tests. It was shown that, during cycling at low loads (the beginning of the test) the EMG activity peaked during the second half of the muscle contraction (the angle in the knee joint was ≈140°); the increase in the load at the end of the test led to a shift of the peak to the beginning of the active phase of movement, while the median frequency of the instant wavelet spectra during the muscle contraction remained almost unchanged. During knee-joint extension, the maximum EMG activity was observed at the very end of the active phase of movement for all loads, and the median frequency significantly increased with increasing angle at the knee joint. The long-term time course of the EMG intensity growth during these tests also differed, whereas the changes in the wavelet-spectrum median frequencies were practically the same: they increased during both tests.

Discrimination of floor cover of dry deciduous forest using Hyperion (EO-1) data

A study was conducted to analyze high spectral reflectance data of the floor cover of dry deciduous forests (Shoolpaneshwar wildlife sanctuary, Gujarat, India) during the summer season. Hyperion data and field data were acquired in the month of April, 2006 (dry/summer season) when the vegetation was in different stages of senescence. Variations in spectral characteristics of different types of leaf litter were seen. Spectral reflectance curves were different for different thicknesses of leaf litter. Altitude also had an impact on the reflectance curves. Spectra of bare soil is easily separable from the ones covered by litter. Descriptive spectra were extracted for four cover types such as Tectona grandis L., Dendrocalamus strictus Nees., mixed deciduous species and bare soil. Continuum removal spectra were also extracted for these four types. Sharp absorption features were seen in VIS and SWIR-II wavelengths which were absent in the spectra of bare soil, indicating the ability of Hyperion data to discriminate dry forest floor from bare soil. The three cover types are also distinctly separable. SWIR-II wavelengths are more sensitive to the type of floor cover indicating its distinctiveness. Results are discussed highlighting the potential of Hyperion data in deciphering floor cover characteristics in the dry season.

Two‐step linear regression based on spectral absorption to detect cyanobacteria in fresh water

A simple spectral absorption method based on two‐step linear regression was used to identify and estimate the quantity of cyanobacteria (Cyanophyceae) among other phytoplankton species in mixed freshwater populations. We focused on four major algal groups, the Cyanophyceae, Chloro‐phyceae, Bacillariophyceae, and Dinophyceae, as typical representatives in the fresh waters of the kanto region of Japan, and dissolved organic carbon (DOC). In the first step, simple linear regression analysis was applied to determine the relationship between spectral absorption characteristics and concentration for each pure sample which contained only one of the four algal groups or DOC. In the second step, the resultant characteristics represented by gradient vectors were used to estimate concentrations of the four algal species and DOC in mixed samples by multiple linear regression analysis. We used the method described here to estimate the quantity of cyanobacteria among algal communities cultured in the laboratory under four different light conditions and in field samples. The method accounted for variations in the spectral characteristics of cyanobacteria owing to different light conditions, which were caused by changes in the ratio of phycocyanin to chlorophyll a. Variations in spectral characteristics of cyanobacteria under different light conditions were assessed geometrically using a vector subspace method based on principal component analysis (PCA). The vector subspace method allowed a detailed study of spectral variation of cyanobacteria recognition under different light conditions in 3‐D space.

Audio watermarking: a way to stationnarize audio signals

Audio watermarking is usually used as a multimedia copyright protection tool or as a system that embed metadata in audio signals. In this paper, watermarking is viewed as a preprocessing step for further audio processing systems: the watermark signal conveys no information, rather it is used to modify the statistical characteristics of an audio signal, in particular its nonstationarity. The embedded watermark is then added in order to stationnarize the host signal. Indeed, the embedded watermark is piecewise stationary, thus it modifies the stationarity of the original audio signal. In some audio processing fields, this fact can be used to improve performances that are very sensitive to time-variant signal statistics. This work presents an analysis of the perceptual watermarking impact on the stationarity of audio signals. The study is based on stationarity indices, which represent a measure of variations in spectral characteristics of signals, using time-frequency representations. Simulation results with two kinds of signals, artificial signals and audio signals (speech and music), are presented. Stationarity indices comparison between watermarked and original audio signals shows a significant stationarity enhancement of the watermarked signal, especially for transient attacks.

Audio watermarking: a way to stationnarize audio signals

Audio watermarking is usually used as a multimedia copyright protection tool or as a system that embed metadata in audio signals. In this paper, watermarking is viewed as a preprocessing step for further audio processing systems: the watermark signal conveys no information, rather it is used to modify the statistical characteristics of an audio signal, in particular its nonstationarity. The embedded watermark is then added in order to stationnarize the host signal. Indeed, the embedded watermark is piecewise stationary, thus it modifies the stationarity of the original audio signal. In some audio processing fields, this fact can be used to improve performances that are very sensitive to time-variant signal statistics. This work presents an analysis of the perceptual watermarking impact on the stationarity of audio signals. The study is based on stationarity indices, which represent a measure of variations in spectral characteristics of signals, using time-frequency representations. Simulation results with two kinds of signals, artificial signals and audio signals (speech and music), are presented. Stationarity indices comparison between watermarked and original audio signals shows a significant stationarity enhancement of the watermarked signal, especially for transient attacks.

Spectral characterization and LAI modelling for the tea ( Camellia sinensis (L.) O. Kuntze) canopy

Understanding the spectral characteristics of tea plants is important in monitoring tea plantations by remote sensing. Westhall tea estate, Kataboola, situated in the Kandy district in Sri Lanka, was selected as the study site. The Leaf Area Index (LAI) of the tea canopy and spectral reflectance of different types of tea clones for different pruning ages were studied in 50 tea fields in the estate. An empirical model between Normalized Difference Vegetation Index (NDVI) (spectrophotometer derived) and LAI (field measured) of the tea canopy was developed. This study has revealed that different tea clones have unique spectral characteristics depending on the tea canopy structure, size, greenness and maturity of the leaves. These spectral variations were also studied using IRS-1C image acquired on the sampling date. Satellite sensor records have shown variation in spectral characteristics for different types of clonal and seedling tea, but these variations are not as prominent as the result offered by spectrophotometer-based observations.