4 research outputs found
Understanding satellite-derived bathymetry using Sentinel 2 imagery and spatial prediction models
ABSTRACT
Optical satellite data is an efficient and complementary method to hydrographic surveys for
deriving bathymetry in shallow coastal waters. Empirical approaches (in particular, the models
of Stumpf and Lyzenga) provide a practical methodology to derive bathymetric information
from remote sensing. Recent studies, however, have focused on enhancing the performance
of such empirical approaches by extending them via spatial information. In this study, the
relationship between multibeam depth and Sentinel-2 image bands was analyzed in an
optically complex environment using the spatial predictor of kriging with an external drift
(KED), where its external drift component was estimated: a) by a ratio of log-transformed
bands based on Stumpf’s model (KED_S) and b) by a log-linear transform based on Lyzenga’s
model (KED_L). Through the calibration of KED models, the study objectives were: 1) to better
understand the empirical relationship between Sentinel-2 multispectral satellite reflectance
and depth, 2) to test the robustness of KED to derive bathymetry in a multitemporal series of
Sentinel-2 images and multibeam data, and 3) to compare the performance of KED against
the existing non-spatial models described by Stumpf et al. and Lyzenga. Results showed that
KED could improve prediction accuracy with a decrease in RMSE of 89% and 88%, and an
increase in R2 of 27% and 14%, over the Stumpf and Lyzenga models, respectively. The
decrease in RMSE provides a worthwhile improvement in accuracy, where results showed
effective prediction of depth up to 6 m. However, the presence of higher concentrations of
suspended materials, especially river plumes, can reduce this threshold to 4 m. As would be
expected, prediction accuracy could be improved through the removal of outliers, which were
mainly located in the channel of the river, areas influenced by the river plume, abrupt
topography, but also very shallow areas close to the shoreline. These areas have been
identified as conflictive zones where satellite-derived bathymetry can be compromised
Energy and environmental forensic analysis of public buildings
This paper outlines a forensic method for analysing the energy, environmental and comfort performance of a building. The method has been applied to a recently developed event space in an Irish public building, which was evaluated using on-site field studies, data analysis, building simulation and occupant surveying. The method allows for consideration of both the technological and anthropological aspects of the building in use and for the identification of unsustainable operational practice and emerging problems. The forensic analysis identified energy savings of up to 50%, enabling a more sustainable, lower-energy operational future for the building. The building forensic analysis method presented in this paper is now planned for use in other public and commercial buildings