Megan Lewis's research while affiliated with University of Adelaide and other places
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Publications (16)
Effective monitoring of arid and semi-arid rangelands around the world is essential to understand and combat degradation caused by anthropogenic use and facilitate effective management practices. Remote sensing technologies provide ideal approaches for enhancing traditional on-ground monitoring. However, while broad-scale monitoring of vegetation i...
Seagrasses are considered indicators of anthropogenic impact but surprisingly little is known about their temporal and spatial dynamics in impacted seascapes. In this study, we used three decades of Landsat imagery (1988–2018) off the coast of Adelaide, South Australia, to investigate how seagrass cover over 501 km² responds to changes in land-base...
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
New, accurate and generalizable methods are required to transform the ever-increasing amount of raw hyperspectral data into actionable knowledge for applications such as environmental monitoring and precision agriculture. Here, we apply advances in generative deep learning models to produce realistic synthetic hyperspectral vegetation data, whilst...
Seagrasses are regarded as indicators and first line of impact for anthropogenic activities affecting the
coasts. The underlying mechanisms driving seagrass cover however have been mostly studied on small
scales, making it difficult to establish the connection to seagrass dynamics in an impacted seascape.
In this study, hyperspectral airborne image...
Key alteration minerals associated with epithermal and porphyry Cu–Au mineralisation have been successfully identified using HyMap airborne hyperspectral imagery in a regolith-dominated terrain in the southern Gawler Ranges, South Australia. Alteration assemblages were mapped using Spectral Feature Fitting, a spectral matching algorithm, identifyin...
Mosquito breeding habitat identification often relies on slow, labour-intensive and expensive ground surveys. With advances in remote sensing and autonomous flight technologies, we endeavoured to accelerate this detection by assessing the effectiveness of a drone multispectral imaging system to determine areas of shallow inundation in an intertidal...
Cover: The cover image is based on the Research Article Reflecting on siliceous rocks in central Australia: Using advanced remote sensing to map ancient “tool‐stone‐ resources by Wallace Boone Law et al., https://doi.org/10.1002/gea.21776.
Hyperspectral sensing, measuring reflectance over visible to shortwave infrared wavelengths, has enabled the classification and mapping of vegetation at a range of taxonomic scales, often down to the species level. Classification with hyperspectral measurements, acquired by narrow band spectroradiometers or imaging sensors, has generally required s...
HyMap™ airborne hyperspectral imagery was used to discriminate and map hydrated silica mineralization in the Dalhousie Springs area of central Australia. A spectral feature fitting algorithm was used to match laboratory reference spectra with image pixel spectra, producing a scaled goodness‐of‐fit raster map of silicified “tool‐stone” sources in ou...
The collection of high-quality field measurements of ground cover is critical for calibration and validation of fractional ground cover maps derived from satellite imagery. Field-based hyperspectral ground cover sampling is a potential alternative to traditional in situ techniques. This study aimed to develop an effective sampling design for spectr...
Remotely sensed ground cover maps are routinely validated using field data collected by observers who classify ground cover into defined categories such as photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), bare soil (BS), and rock. There is an element of subjectivity to the classification of PV and NPV, and classifications may di...
An objective method for generating statistically sound objective regolith-landform maps using widely accessible digital topographic and geophysical data without requiring specific regional knowledge is demonstrated and has application as a first pass tool for mineral exploration in regolith dominated terrains. This method differs from traditional r...
Poster presentation at the 2017 Australian Archaeological Association Conference - Melbourne.
The South Australian (SA) Department of Environment, Water and Natural Resources (DEWNR) seeks to develop new methods for mapping and monitoring fire, particularly for more regional and outback areas. Here, mapping of fire scars is not done consistently, and a variety of manual and semi-automated techniques have been used over the years. A number o...
Citations
... The loss of >40 % of the original (local) seagrass cover prompted management agencies to agree on aspirational load reductions for both nitrogen (by 75 % to 600 t) and suspended solids (by 50 % to 4200 t) (Fox et al., 2007;McDowell and Pfennig, 2013). A significant reduction of nitrogen (>70 %) and solids (>50 %) in effluents from wastewater treatment plants has subsequently been accomplished (Fernandes and Dinesh, 2018), resulting in considerable water quality improvements along the Adelaide coast over the past three decades (Fernandes et al., 2022). Despite these efforts, signs of initial seagrass recovery were slow to appear, particularly in the nearshore (Bryars and Neverauskas, 2004;DEWNR, 2013). ...
... De nombreuses approches permettent d'augmenter artificiellement la quantité de données pour les techniques d'apprentissage : l'injection de bruit [163], les stratégies de relighting [164], la génération d'images hyperspectrales à partir d'images RGB [165], la génération d'images hyperspectrales synthétiques [166,167,168,169], etc... Notons également l'intérêt grandissant pour les méthodes de transfert d'apprentissage entre les premières couches de réseaux convolutifs pré-entraînés sur images RGB vers des réseaux développés pour la segmentation d'images hyperspectrales [170,171,172]. ...
... Extra drag by the presence of seagrass was estimated using Dynveg, a model that takes into account the plant properties and reconfiguration (bending) in the flow (Dijkstra and Uittenbogaard, 2010). Plant biomechanical properties were selected for Posidonia spp., which constitute around 80 % of cover in Adelaide's coastal waters (Clarke et al., 2021). Representative bottom roughness coefficients were estimated (Table S1) and applied to grid cells according to seagrass cover mapped by the South Australian Department for Environment and Water based on data collected in (EnviroDataSA, 2015. ...
... It should be noted that with this method, the global accuracies were up to 98.56%. Despite other classification methodologies being better for the identification of minerals and the generation of lithological maps such as SVM, RF, and CNN, the most used classifier is SAM which, as mentioned above, does not work very well when there are not enough training data [28,96,107]. In geological studies, it is quite difficult to obtain a lot of training data due to difficult access areas as in the case of [105] where a lithological map of an area formed by the Teide-Pico Viejo stratovolcano was made. ...
... UAVs are multipurpose platforms to which a variety of sensory equipment can be mounted. Based on user preference, UAVs can utilize passive sensors that capture reflected rays of electromagnetic radiation such as thermal, near infrared or visible spectrum, or combinations thereof in hyperspectral cameras [27,34,35]. Additionally, these systems may incorporate active sensors, such as radar or lidar which characterize the three-dimensional structure of terrain and vegetation. ...
... HSI is an emerging method that analyzes a wide range of wavelengths instead of only providing each pixel one of the three primary colors [31,32]. HSI has been used in numerous classifications fields, such as agriculture [33], cancer detection [34][35][36][37], military [38], air pollution detection [29,39], remote sensing [40], dental imaging [41], environment monitoring [42], satellite photography [43], counterfeit verification [44][45][46], forestry monitoring [47], food security [48], natural resource surveying [49], vegetation observation [50], and geological mapping [51]. ...
... Big data platforms like the GEE facilitate the comparison of images over a long period, allowing appreciating changes over time. This is apart from the time and cost-effectiveness of remotely sensed data compared to traditional statistical surveys [72]. Improved irrigated areas improve water allocation to farmers, irrigation performance and intensity assessment, and environmental impact assessment, thereby improving irrigation water use efficiency. ...
... Direct observation of photosynthetic cover is also subject to human bias, for example, decisions on whether a yellow leaf counts as photosynthetic or not. In contrast, sensor-based observations present continuous measurements of greenness that can reduce bias (Fisk et al., 2019). Despite these challenges, we believe comparisons of UAS data products and traditional field methods are still valuable, for example, to understand how contemporary UAS imagery relates to historical data. ...
... Modern data analytics technology and the advances in satellite imaging provide access to large datasets that can assist in characterising landscape features and their distribution at regional scales (e.g. Wilford et al. 2016;Jasiewicz et al. 2014Jasiewicz et al. , 2015de Caritat et al. 2017;Caruso et al. 2018;Albrecht et al. 2021). ...
... Traditional survey methods of the abundance or spatial distribution of animal populations have recently been replaced by non-invasively applied conservation drones and image processing techniques [38][39][40][41][42][43]. These aerial methods can decrease the high costs and labor requirements; overcome difficult access to large, remote areas; and increase the accuracy and precision of estimation. ...