scholarly journals Hyperspectral Monitoring of Non-Native Tropical Grasses over Phenological Seasons

2021 ◽  
Vol 13 (4) ◽  
pp. 738
Author(s):  
Kirrilly Pfitzner ◽  
Renee Bartolo ◽  
Tim Whiteside ◽  
David Loewensteiner ◽  
Andrew Esparon
Keyword(s):  
Near Infrared ◽  
Spectral Response ◽  
Grass Species ◽  
Wet Season ◽  
Native Grass ◽  
Data Collections ◽  
Spectral Patterns ◽  
Shortwave Infrared ◽  
Over Time

The miniaturisation of hyperspectral sensors for use on drones has provided an opportunity to obtain hyper temporal data that may be used to identify and monitor non-native grass species. However, a good understanding of variation in spectra for species over time is required to target such data collections. Five taxological and morphologically similar non-native grass species were hyper spectrally characterised from multitemporal spectra (17 samples over 14 months) over phenological seasons to determine their temporal spectral response. The grasses were sampled from maintained plots of homogenous non-native grass cover. A robust in situ standardised sampling method using a non-imaging field spectrometer measuring reflectance across the 350–2500 nm wavelength range was used to obtain reliable spectral replicates both within and between plots. The visible-near infrared (VNIR) to shortwave infrared (SWIR) and continuum removed spectra were utilised. The spectra were then resampled to the VNIR only range to simulate the spectral response from more affordable VNIR only hyperspectral scanners suitable to be mounted on drones. We found that species were separable compared to similar but different species. The spectral patterns were similar over time, but the spectral shape and absorption features differed between species, indicating these subtle characteristics could be used to distinguish between species. It was the late dry season and the end of the wet season that provided maximum separability of the non-native grass species sampled. Overall the VNIR-SWIR results highlighted more dissimilarity for unlike species when compared to the VNIR results alone. The SWIR is useful for discriminating species, particularly around water absorption.

scholarly journals Deriving seasonal dynamics in ecosystem properties of semi-arid savanna grasslands from in situ-based hyperspectral reflectance

2015 ◽  
Vol 12 (15) ◽  
pp. 4621-4635 ◽  
Author(s):  
T. Tagesson ◽  
R. Fensholt ◽  
S. Huber ◽  
S. Horion ◽  
I. Guiro ◽  
...  
Keyword(s):  
Seasonal Dynamics ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Arid Ecosystems ◽  
Hyperspectral Reflectance ◽  
Data Set ◽  
Ecosystem Properties ◽  
Shortwave Infrared ◽  
Semi Arid

Abstract. This paper investigates how hyperspectral reflectance (between 350 and 1800 nm) can be used to infer ecosystem properties for a semi-arid savanna grassland in West Africa using a unique in situ-based multi-angular data set of hemispherical conical reflectance factor (HCRF) measurements. Relationships between seasonal dynamics in hyperspectral HCRF and ecosystem properties (biomass, gross primary productivity (GPP), light use efficiency (LUE), and fraction of photosynthetically active radiation absorbed by vegetation (FAPAR)) were analysed. HCRF data (ρ) were used to study the relationship between normalised difference spectral indices (NDSIs) and the measured ecosystem properties. Finally, the effects of variable sun sensor viewing geometry on different NDSI wavelength combinations were analysed. The wavelengths with the strongest correlation to seasonal dynamics in ecosystem properties were shortwave infrared (biomass), the peak absorption band for chlorophyll a and b (at 682 nm) (GPP), the oxygen A band at 761 nm used for estimating chlorophyll fluorescence (GPP and LUE), and blue wavelengths (ρ412) (FAPAR). The NDSI with the strongest correlation to (i) biomass combined red-edge HCRF (ρ705) with green HCRF (ρ587), (ii) GPP combined wavelengths at the peak of green reflection (ρ518, ρ556), (iii) LUE combined red (ρ688) with blue HCRF (ρ436), and (iv) FAPAR combined blue (ρ399) and near-infrared (ρ1295) wavelengths. NDSIs combining near infrared and shortwave infrared were strongly affected by solar zenith angles and sensor viewing geometry, as were many combinations of visible wavelengths. This study provides analyses based upon novel multi-angular hyperspectral data for validation of Earth-observation-based properties of semi-arid ecosystems, as well as insights for designing spectral characteristics of future sensors for ecosystem monitoring.

scholarly journals Mapping homogeneous spectral response zones in a soil profile

2018 ◽  
Author(s):  
Edward J. Jones ◽  
Alex B. McBratney
Keyword(s):  
Soil Profile ◽  
Near Infrared ◽  
Diffuse Reflectance Spectroscopy ◽  
Spectral Response ◽  
Principal Component ◽  
External Parameter ◽  
Dry Conditions ◽  
Soil Units ◽  
Moisture Conditions

Abstract. Homogeneous spectral response zones represent relatively uniform regions of soil that may be useful for identifying soil horizons or delineating soil units spatially. External parameter orthogonalisation (EPO) and direct standardisation (DS) were assessed for their ability to conserve intrinsic soil information of spectra under variable moisture conditions, as experienced when taking measurements in situ. A 1 m × 1 m section of a soil profile was intensively sampled using visible near-infrared diffuse reflectance spectroscopy at 2.5 cm vertical intervals and 10 cm horizontal intervals. Further samples were taken on a 10 cm grid and scanned in a laboratory under field moist and air-dry conditions. A principal component space was constructed based on the in situ scans following either EPO transformation, DS transformation or following pre-processing only (PP). Scores from the first four principal components – which accounted for more than 0.97 of the total variance in each case – were subject to k-means clustering to identify homogeneous spectral response zones. Laboratory-based scans were then projected onto the same principal component space and fitted to the pre-existing cluster centroids. Both EPO and DS were found to have potential in reconciling differences observed between in situ and laboratory-based measurements compared to pre-processing only (PP). EPO outperformed DS in terms of conserving the relationship between PC scores (LCCC: EPO = 0.84, DS = 0.58, PPO = 0.44; RMSE: EPO = 11.8, DS = 15.4, PPO = 38.5) and also in identifying homogeneous spectral response zones that corresponded to field observed horizons.

scholarly journals Determination of the TROPOMI-SWIR instrument spectral response function

2018 ◽  
Vol 11 (7) ◽  
pp. 3917-3933 ◽  
Author(s):  
Richard M. van Hees ◽  
Paul J. J. Tol ◽  
Sidney Cadot ◽  
Matthijs Krijger ◽  
Stefan T. Persijn ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Monochromatic Light ◽  
Imaging Spectrometer ◽  
Swir Band ◽  
Shortwave Infrared ◽  
Single Instrument

Abstract. The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board the ESA Copernicus Sentinel-5 Precursor satellite. TROPOMI is a nadir-viewing imaging spectrometer with bands in the ultraviolet and visible, the near infrared and the shortwave infrared (SWIR). An accurate instrument spectral response function (ISRF) is required in the SWIR band where absorption lines of CO, methane and water vapor overlap. In this paper, we report on the determination of the TROPOMI-SWIR ISRF during an extensive on-ground calibration campaign. Measurements are taken with a monochromatic light source scanning the whole detector, using the spectrometer itself to determine the light intensity and wavelength. The accuracy of the resulting ISRF calibration key data is well within the requirement for trace-gas retrievals. Long-term in-flight monitoring of SWIR ISRF is achieved using five on-board diode lasers.

scholarly journals The operational methane retrieval algorithm for TROPOMI

2016 ◽  
Vol 9 (11) ◽  
pp. 5423-5440 ◽  
Author(s):  
Haili Hu ◽  
Otto Hasekamp ◽  
André Butz ◽  
André Galli ◽  
Jochen Landgraf ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Retrieval Algorithm ◽  
Model Errors ◽  
Instrument Calibration ◽  
Atmospheric Scattering ◽  
Accuracy And Precision ◽  
Land Surfaces ◽  
Shortwave Infrared

Abstract. This work presents the operational methane retrieval algorithm for the Sentinel 5 Precursor (S5P) satellite and its performance tested on realistic ensembles of simulated measurements. The target product is the column-averaged dry air volume mixing ratio of methane (XCH4), which will be retrieved simultaneously with scattering properties of the atmosphere. The algorithm attempts to fit spectra observed by the shortwave and near-infrared channels of the TROPOspheric Monitoring Instrument (TROPOMI) spectrometer aboard S5P.The sensitivity of the retrieval performance to atmospheric scattering properties, atmospheric input data and instrument calibration errors is evaluated. In addition, we investigate the effect of inhomogeneous slit illumination on the instrument spectral response function. Finally, we discuss the cloud filters to be used operationally and as backup.We show that the required accuracy and precision of  < 1 % for the XCH4 product are met for clear-sky measurements over land surfaces and after appropriate filtering of difficult scenes. The algorithm is very stable, having a convergence rate of 99 %. The forward model error is less than 1 % for about 95 % of the valid retrievals. Model errors in the input profile of water do not influence the retrieval outcome noticeably. The methane product is expected to meet the requirements if errors in input profiles of pressure and temperature remain below 0.3 % and 2 K, respectively. We further find that, of all instrument calibration errors investigated here, our retrievals are the most sensitive to an error in the instrument spectral response function of the shortwave infrared channel.

scholarly journals Deriving seasonal dynamics in ecosystem properties of semi-arid savannas using in situ based hyperspectral reflectance

2015 ◽  
Vol 12 (4) ◽  
pp. 3315-3347
Author(s):  
T. Tagesson ◽  
R. Fensholt ◽  
S. Huber ◽  
S. Horion ◽  
I. Guiro ◽  
...  
Keyword(s):  
Seasonal Dynamics ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Arid Ecosystems ◽  
Hyperspectral Reflectance ◽  
Ecosystem Properties ◽  
Shortwave Infrared ◽  
Reflectance Data ◽  
Semi Arid

Abstract. This paper investigates how seasonal hyperspectral reflectance data (between 350 and 1800 nm) can be used to infer ecosystem properties for a semi-arid savanna ecosystem in West Africa using a unique in situ based dataset. Relationships between seasonal dynamics in hyperspectral reflectance, and ecosystem properties (biomass, gross primary productivity (GPP), light use efficiency (LUE), and fraction of photosynthetically active radiation absorbed by vegetation (FAPAR)) were analysed. Reflectance data (ρ) were used to study the relationship between normalised difference spectral indices (NDSI) and the measured ecosystem properties. Finally, also the effects of variable sun sensor viewing geometry on different NDSI wavelength combinations were analysed. The wavelengths with the strongest correlation to seasonal dynamics in ecosystem properties were shortwave infrared (biomass), the peak absorption band for chlorophyll a and b (at 682 nm) (GPP), the oxygen A-band at 761 nm used for estimating chlorophyll fluorescence (GPP, and LUE), and blue wavelengths (FAPAR). The NDSI with the strongest correlation to: (i) biomass combined red edge reflectance (ρ705) with green reflectance (ρ587), (ii) GPP combined wavelengths at the peak of green reflection (ρ518, ρ556), (iii) the LUE combined red (ρ688) with blue reflectance (ρ436), and (iv) FAPAR combined blue (ρ399) and near infrared (ρ1295) wavelengths. NDSI combining near infrared and shortwave infrared were strongly affected by solar zenith angles and sensor viewing geometry, as were many combinations of visible wavelengths. This study provides analyses based upon novel multi-angular hyperspectral data for validation of Earth Observation based properties of semi-arid ecosystems, as well as insights for designing spectral characteristics of future sensors for ecosystem monitoring.

Dormancy and Germination in Five Native Grass Species From Savannah Woodland Communities of the Northern Territory

1978 ◽  
Vol 26 (5) ◽  
pp. 621 ◽  
Author(s):  
JJ Mott
Keyword(s):  
Soil Surface ◽  
Moisture Stress ◽  
Northern Territory ◽  
Grass Species ◽  
Wet Season ◽  
Native Grass ◽  
Native Grasslands ◽  
Similar Range ◽  
Seed Fall ◽  
C 30

The dormancy and germination requirements of five native grass species (Themeda australis, Chrysopogon fallax, C. latifolius, Sorghum plumosum, S. stipoideum) from the savannah woodlands of the Northern Territory were studied under controlled conditions. Results were related to the ecology of these species in the native grasslands of the region. All species were dormant at seed fall, and dormancy was found to be broken by exposure to dry heat. Gibberellic acid was also found to have a stimulatory effect on germination of dormant seed but there was no effect on stratification. In the field, temperatures existent at the soil surface during the dry season ensure that dormancy was broken before the heavy rainfall of the following wet season. Seeds of all species studied germinated over a similar range of temperatures with optimum germination at high temperature (c. 30°C). Although seeds of all species were not adapted to germina- tion under moisture stress, the existence of sharply pointed calluses and hygroscopically active awns on the seeds ensured that they would be buried below the moisture extremes of the immediate soil surface.

Species, climate and fertilizer effects on grass fibre and protein in tropical environments

2009 ◽  
Vol 147 (5) ◽  
pp. 555-568 ◽  
Author(s):  
H. TRAN ◽  
P. SALGADO ◽  
P. LECOMTE
Keyword(s):  
Growth Rate ◽  
Near Infrared ◽  
Protein Fractions ◽  
Grass Species ◽  
Insoluble Protein ◽  
Wet Season ◽  
Near Infrared Reflectance ◽  
Tropical Environments ◽  
Acid Detergent Fibre ◽  
Chloris Gayana

SUMMARYA 3-year experiment (2005–07) was conducted on Reunion Island (France) to evaluate the effect of species, climate and fertilization levels on fibre and protein fractions of tropical (C4; Chloris gayana and Pennisetum clandestinum) and temperate (C3; Dactylis glomerata and Lotium multiflorum) grasses. A near infrared reflectance spectroscopy (NIRS) prediction referential was developed to estimate neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP), NDF insoluble protein (NDF-IP) and ADF insoluble protein (ADF-IP). The NIRS equations were then used to screen many regrowth grass samples collected at heading stage continuously for 3 years to evaluate their changes during the seasons. Results showed that grass species differed significantly in fibre and protein fractions. NDF, ADF and ADF-IP were the lowest in D. glomerata/L. multiflorum and the highest in C. gayana. The wet season was associated with higher NDF, ADF and NDF-IP in D. glomerata/L. multiflorum and lower NDF-IP in P. clandestinum. Fertilization increased the CP in C. gayana and the NDF-IP in P. clandestinum, but decreased the ADF-IP of both C. gayana and D. glomerata/L. multiflorum. Growth rate strongly changed NDF, ADF, NDF-IP and ADF-IP although no change in CP appeared. In general, NDF, ADF and NDF-IP increased with the growth rate. In contrast, the ADF-IP content decreased from slow to fast growth rate in C. gayana and D. glomerata/L. multiflorum. Growth rate changes were thus considered as a general indicator for fibre and protein fraction variations of these grasses.

Phenology affects differentiation of crop and weed species using hyperspectral remote sensing

2020 ◽  
Vol 34 (6) ◽  
pp. 897-908
Author(s):  
Nicholas T. Basinger ◽  
Katherine M. Jennings ◽  
Erin L. Hestir ◽  
David W. Monks ◽  
David L. Jordan ◽  
...  
Keyword(s):  
Near Infrared ◽  
Canopy Structure ◽  
Growing Season ◽  
Plant Phenology ◽  
Species Differentiation ◽  
In Situ Spectroscopy ◽  
Weed Species ◽  
Leaf Level ◽  
Shortwave Infrared

AbstractThe effect of plant phenology and canopy structure of four crops and four weed species on reflectance spectra were evaluated in 2016 and 2017 using in situ spectroscopy. Leaf-level and canopy-level reflectance were collected at multiple phenologic time points in each growing season. Reflectance values at 2 wk after planting (WAP) in both years indicated strong spectral differences between species across the visible (VIS; 350–700 nm), near-infrared (NIR; 701–1,300 nm), shortwave-infrared I (SWIR1; 1,301–1,900 nm), and shortwave-infrared II (SWIR2; 1,901–2,500 nm) regions. Results from this study indicate that plant spectral reflectance changes with plant phenology and is influenced by plant biophysical characteristics. Canopy-level differences were detected in both years across all dates except for 1 WAP in 2017. Species with similar canopy types (e.g., broadleaf prostrate, broadleaf erect, or grass/sedge) were more readily discriminated from species with different canopy types. Asynchronous phenology between species also resulted in spectral differences between species. SWIR1 and SWIR2 wavelengths are often not included in multispectral sensors but should be considered for species differentiation. Results from this research indicate that wavelengths in SWIR1 and SWIR2 in conjunction with VIS and NIR reflectance can provide differentiation across plant phenologies and, therefore should be considered for use in future sensor technologies for species differentiation.

scholarly journals Classificação Espectral de Fitofisionomias em Área de Floresta Tropical Utilizando Dados do Sensor Aster

2019 ◽  
Vol 23 (2) ◽  
pp. 132
Author(s):  
Gustavo Manzon Nunes ◽  
Carlos Roberto De Souza Filho ◽  
Laerte Guimarães Ferreira ◽  
Luiz Eduardo Vicente ◽  
Maricéia Tatiana Vilani
Keyword(s):  
Sustainable Development ◽  
Near Infrared ◽  
Thermal Emission ◽  
Matched Filtering ◽  
Spectral Angle Mapper ◽  
Ndvi Index ◽  
Close Relationship ◽  
Spectral Patterns ◽  
Shortwave Infrared ◽  
Spectral Angle

Este artigo pretende avaliar a capacidade dos dados gerados pelo sensor Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)/Terra, na discriminação de fitofisionomias existentes na Reserva de Desenvolvimento Sustentável Amanã (RDSA). Os dados ASTER analisados incluem os intervalos espectrais do visível (0.52-0.69 μm), infravermelho próximo (0.78-0.86 μm) e infravermelho de ondas curtas (1.60 a 2.43 μm), sendo que nas bandas destes intervalos foram aplicadas técnicas de classificação espectral adaptadas para os dados deste sensor como Spectral Angle Mapper (SAM), Mixture Tuned Matched Filtering (MTMF), além do NDVI. Através da técnica SAM foi possível a discriminação de seis fitofisionomias predominantes na RDSA. Através da técnica MTMF, que envolve um algoritmo de classificação mais robusto, informações equivalentes foram obtidas. Foi possível ainda a associação e detecção dos padrões espectrais da cobertura vegetal, mostrando a estreita relação com o índice NDVI. Palavras-chave: Mapeamento. Reserva de Desenvolvimento Sustentável Amanã. Vegetação.  Abstract This article aims to evaluate the data capacity created by a sensor named Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)/Terra, in the phytophysiognomies description of Amanã Sustainable Development Reserve (RDSA). The ASTER data analyzed include the spectral intervals of visible (0.52-0.69 μm), near-infrared (0.78-0.86 μm) and shortwave infrared (1.60 to 2:43 μm), wherein these intervals bands were applied the spectral classification techniques adapted to the data from this sensor as Spectral Angle Mapper (SAM), Mixture Tuned Matched Filtering (MTMF) plus NDVI. By SAM technique was possible to distinguish six predominant phytophysiognomies in the RDSA. By MTMF technique that involves a more robust classification algorithm, equivalent information was obtained. It was also possible to associate and detect spectral patterns of vegetation, showing the close relationship with the NDVI index. Keywords: Amanã Sustainable Development Reserve. Mapping. Vegetation. 

Two-Dimensional Near-Infrared and Shortwave Infrared Molecular Aggregates: Taking Kasha’s Model to the Next Dimension

2019 ◽  
Author(s):  
Arundhati Deshmukh ◽  
Danielle Koppel ◽  
Chern Chuang ◽  
Danielle Cadena ◽  
Jianshu Cao ◽  
...  
Keyword(s):  
Near Infrared ◽  
Photophysical Properties ◽  
Satellite Telemetry ◽  
Transition Dipole Moment ◽  
Short Wave ◽  
Tissue Imaging ◽  
Transition Dipole ◽  
Deep Tissue Imaging ◽  
Excitonic States ◽  
Shortwave Infrared

Technologies which utilize near-infrared (700 – 1000 nm) and short-wave infrared (1000 – 2000 nm) electromagnetic radiation have applications in deep-tissue imaging, telecommunications and satellite telemetry due to low scattering and decreased background signal in this spectral region. However, there are few molecular species, which absorb efficiently beyond 1000 nm. Transition dipole moment coupling (e.g. J-aggregation) allows for redshifted excitonic states and provides a pathway to highly absorptive electronic states in the infrared. We present aggregates of two cyanine dyes whose absorption peaks redshift dramatically upon aggregation in water from ~ 800 nm to 1000 nm and 1050 nm with sheet-like morphologies and high molar absorptivities (e ~ 10<sup>5 </sup>M<sup>-1</sup>cm<sup>-1</sup>). To describe this phenomenology, we extend Kasha’s model for J- and H-aggregation to describe the excitonic states of <i> 2-dimensional aggregates</i> whose slip is controlled by steric hindrance in the assembled structure. A consequence of the increased dimensionality is the phenomenon of an <i>intermediate </i>“I-aggregate”, one which redshifts yet displays spectral signatures of band-edge dark states akin to an H-aggregate. We distinguish between H-, I- and J-aggregates by showing the relative position of the bright (absorptive) state within the density of states using temperature dependent spectroscopy. Our results can be used to better design chromophores with predictable and tunable aggregation with new photophysical properties.

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