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Near-infrared digital hemispherical photography enables correction of plant area index for woody material during leaf-on conditions (2023)
Journal Article

Indirect optical measurement techniques enable efficient and non-destructive estimation of plant area index (PAI). However, because they cannot distinguish between foliage and other canopy elements, corrections are needed to determine leaf area index... Read More about Near-infrared digital hemispherical photography enables correction of plant area index for woody material during leaf-on conditions.

HemiPy: A Python module for automated estimation of forest biophysical variables and uncertainties from digital hemispherical photographs (2023)
Journal Article

Digital hemispherical photography (DHP) is widely used to derive forest biophysical variables including leaf, plant, and green area index (LAI, PAI and GAI), the fraction of intercepted photosynthetically active radiation (FIPAR), and the fraction of... Read More about HemiPy: A Python module for automated estimation of forest biophysical variables and uncertainties from digital hemispherical photographs.

Assessment of active LiDAR data and passive optical imagery for double-layered mangrove leaf area index estimation: a case study in Mai Po, Hong Kong (2023)
Journal Article
Li, Q., Wong, F. K. K., Kwan, F., Wong, K., Fung, T., Brown, L. A., & Dash, J. (2023). Assessment of active LiDAR data and passive optical imagery for double-layered mangrove leaf area index estimation: a case study in Mai Po, Hong Kong. Remote Sensing, 15(10), 2551. https://doi.org/10.3390/rs15102551

Remote sensing technology is a timely and cost-efficient method for leaf area index (LAI) estimation, especially for less accessible areas such as mangrove forests. Confounded by the poor penetrability of optical images, most previous studies focused... Read More about Assessment of active LiDAR data and passive optical imagery for double-layered mangrove leaf area index estimation: a case study in Mai Po, Hong Kong.

The spatio‐temporal distribution of pollen traits related to dispersal and desiccation tolerance in Canarian laurel forest (2022)
Journal Article

Questions
Pollen traits (e.g., size, wall thickness, number of apertures) have been suggested to be relevant in terms of pollination mechanisms and the ability of the male gametophyte to withstand desiccation. We examined the spatiotemporal distribu... Read More about The spatio‐temporal distribution of pollen traits related to dispersal and desiccation tolerance in Canarian laurel forest.

Calibration and characterisation of four chlorophyll meters and transmittance spectroscopy for non-destructive estimation of forest leaf chlorophyll concentration (2022)
Journal Article
Brown, L., Williams, O., & Dash, J. (2022). Calibration and characterisation of four chlorophyll meters and transmittance spectroscopy for non-destructive estimation of forest leaf chlorophyll concentration. Agricultural and forest meteorology, 323, https://doi.org/10.1016/j.agrformet.2022.109059

Chlorophyll meters enable efficient and non-destructive estimation of leaf chlorophyll concentration (LCC), but require calibration against destructively-determined values to provide an absolute quantity that is comparable between different studies a... Read More about Calibration and characterisation of four chlorophyll meters and transmittance spectroscopy for non-destructive estimation of forest leaf chlorophyll concentration.

Evaluation of Sentinel-3A and Sentinel-3B ocean land colour instrument green instantaneous fraction of absorbed photosynthetically active radiation (2021)
Journal Article

This article presents the evaluation of the Copernicus Sentinel-3 Ocean Land Colour Instrument (OLCI) operational terrestrial products corresponding to the green instantaneous Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) and its a... Read More about Evaluation of Sentinel-3A and Sentinel-3B ocean land colour instrument green instantaneous fraction of absorbed photosynthetically active radiation.

Fiducial reference measurements for vegetation bio-geophysical variables: an end-to-end uncertainty evaluation framework (2021)
Journal Article

With a wide range of satellite-derived vegetation bio-geophysical products now available to users, validation efforts are required to assess their accuracy and fitness for purpose. Substantial progress in the validation of such products has been made... Read More about Fiducial reference measurements for vegetation bio-geophysical variables: an end-to-end uncertainty evaluation framework.

Potential of automated digital hemispherical photography and wireless quantum sensors for routine canopy monitoring and satellite product validation (2021)
Presentation / Conference Contribution

To better characterize the temporal dynamics of vegetation biophysical variables, a variety of automated in situ measurement techniques have been developed in recent years. In this study, we investigated automated digital hemispherical photography (D... Read More about Potential of automated digital hemispherical photography and wireless quantum sensors for routine canopy monitoring and satellite product validation.

Validation of baseline and modified Sentinel-2 level 2 prototype processor leaf area index retrievals over the United States (2021)
Journal Article

The Sentinel-2 Level 2 Prototype Processor (SL2P) is made available to users for the retrieval of vegetation biophysical variables including leaf area index (LAI) from Multispectral Instrument (MSI) data within the Sentinel Application Platform (SNAP... Read More about Validation of baseline and modified Sentinel-2 level 2 prototype processor leaf area index retrievals over the United States.

Deriving leaf area index reference maps using temporally continuous data: a comparison of upscaling approaches (2020)
Journal Article
Brown, L., Ogutu, B., Camacho, F., Fuster, B., & Dash, J. (2020). Deriving leaf area index reference maps using temporally continuous data: a comparison of upscaling approaches. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 14, 624-630. https://doi.org/10.1109/JSTARS.2020.3040080

To further progress the validation of global leaf area index (LAI) products, temporally continuous reference data are a key requirement, as periodic field campaigns fail to adequately characterize temporal dynamics. Progress in cost-effective automat... Read More about Deriving leaf area index reference maps using temporally continuous data: a comparison of upscaling approaches.

Low-cost unmanned aerial vehicle-based digital hemispherical photography for estimating leaf area index: a feasibility assessment (2020)
Journal Article
Brown, L., Sutherland, D., & Dash, J. (2020). Low-cost unmanned aerial vehicle-based digital hemispherical photography for estimating leaf area index: a feasibility assessment. International Journal of Remote Sensing, 41(23), 9064-9074. https://doi.org/10.1080/2150704X.2020.1802527

Unmanned aerial vehicles (UAVs) have the potential to provide highly detailed information on vegetation status useful in precision agriculture. However, challenges are associated with existing techniques for UAV-based retrieval of vegetation biophysi... Read More about Low-cost unmanned aerial vehicle-based digital hemispherical photography for estimating leaf area index: a feasibility assessment.

The Sentinel-3 OLCI Terrestrial Chlorophyll Index (OTCI): algorithm improvements, spatiotemporal consistency and continuity with the MERIS archive (2020)
Journal Article
Pastor-Guzman, J., Brown, L., Morris, H., Bourg, L., Goryl, P., Dransfeld, S., & Dash, J. (2020). The Sentinel-3 OLCI Terrestrial Chlorophyll Index (OTCI): algorithm improvements, spatiotemporal consistency and continuity with the MERIS archive. Remote Sensing, 12(16), https://doi.org/10.3390/rs12162652

The Ocean and Land Colour Instrument (OLCI) on-board Sentinel-3 (2016–present) was designed with similar mechanical and optical characteristics to the Envisat Medium Resolution Imaging Spectrometer (MERIS) (2002–2012) to ensure continuity with a numb... Read More about The Sentinel-3 OLCI Terrestrial Chlorophyll Index (OTCI): algorithm improvements, spatiotemporal consistency and continuity with the MERIS archive.

Evaluation of global leaf area index and fraction of absorbed photosynthetically active radiation products over North America using copernicus ground based observations for validation data (2020)
Journal Article

With a growing number of Earth observation (EO) products available through operational programmes such as the European Union’s Copernicus, there is increasing emphasis on product accuracy and uncertainty, necessitating evaluation against in situ refe... Read More about Evaluation of global leaf area index and fraction of absorbed photosynthetically active radiation products over North America using copernicus ground based observations for validation data.

Tracking forest biophysical properties with automated digital repeat photography: a fisheye perspective using digital hemispherical photography from below the canopy (2020)
Journal Article
Brown, L., Ogutu, B., & Dash, J. (2020). Tracking forest biophysical properties with automated digital repeat photography: a fisheye perspective using digital hemispherical photography from below the canopy. Agricultural and forest meteorology, 287, https://doi.org/10.1016/j.agrformet.2020.107944

In recent years, digital repeat photography has received increasing attention as an inexpensive means by which seasonal changes in vegetation canopies can be monitored. Offering automation and an increased measurement frequency, colour indices derive... Read More about Tracking forest biophysical properties with automated digital repeat photography: a fisheye perspective using digital hemispherical photography from below the canopy.

Estimating peanut leaf chlorophyll content with dorsiventral leaf adjusted indices: minimizing the impact of spectral differences between adaxial and abaxial leaf surfaces (2019)
Journal Article

Relatively little research has assessed the impact of spectral differences among dorsiventral leaves caused by leaf structure on leaf chlorophyll content (LCC) retrieval. Based on reflectance measured from peanut adaxial and abaxial leaves and LCC me... Read More about Estimating peanut leaf chlorophyll content with dorsiventral leaf adjusted indices: minimizing the impact of spectral differences between adaxial and abaxial leaf surfaces.

GBOV (Ground-Based Observation for Validation): a copernicus service for validation of vegetation land products (2019)
Presentation / Conference Contribution

The Copernicus Ground-Based Observations for Validation (GBOV) service aims to develop and distribute robust in-situ datasets from a selection of ground-based monitoring sites for a systematic and quantitative validation of Earth Observation (EO) lan... Read More about GBOV (Ground-Based Observation for Validation): a copernicus service for validation of vegetation land products.

Estimating forest leaf area index and canopy chlorophyll content with Sentinel-2: an evaluation of two hybrid retrieval algorithms (2019)
Journal Article
Brown, L., Ogutu, B., & Dash, J. (2019). Estimating forest leaf area index and canopy chlorophyll content with Sentinel-2: an evaluation of two hybrid retrieval algorithms. Remote Sensing, 11(15), https://doi.org/10.3390/rs11151752

Estimates of biophysical and biochemical variables such as leaf area index (LAI) and canopy chlorophyll content (CCC) are a fundamental requirement for effectively monitoring and managing forest environments. With its red-edge bands and high spatial... Read More about Estimating forest leaf area index and canopy chlorophyll content with Sentinel-2: an evaluation of two hybrid retrieval algorithms.