Intertidal Bathymetry Extraction with Multispectral Images: A Logistic Regression Approach

Isabel Bué,Álvaro Semedo,João Catalão

doi:10.3390/rs12081311

Isabel Bué, Álvaro Semedo + Show 1 more

Open Access

https://doi.org/10.3390/rs12081311

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Abstract

In this study, a methodology to estimate the intertidal bathymetry from multispectral remote sensing images is presented. The technique is based on the temporal variability of the water and the intertidal zone reflectance and their correlation with the tidal height. The water spectral behavior is characterized by high absorption at the infrared (IR) band or radiation with higher wavelengths. Due to tidal cycles, pixels on the intertidal zone have higher temporal variability on the near IR spectral reflectance. The variability of IR reflectivity in time is modeled through a sigmoid function of three parameters, where the inflection parameter corresponds to the pixel elevation. The methodology was tested at the Tagus river estuary in Lisbon, Portugal, and at the Bijagós archipelago, in the West African nation of Guinea-Bissau. Multispectral images from Sentinel-2 satellites were used, after atmospheric corrections from ACOLITE processor and the derived bathymetric model validated with in situ data. The presented method does not require additional depth data for calibration, and the output can generate intertidal digital elevation models at 10 m spatial resolution, without any manual editing by the operator. The results show a standard deviation of 0.34 m at the Tagus tidal zone, with −0.50 m bias, performing better than the Stumpf ratio transform algorithm, also applied to the test areas to derive intertidal bathymetry. This methodology can be used to update intertidal elevation models with clear benefits to monitoring of intertidal dynamics, morphodynamic modeling, and cartographic update.

Highlights

The intertidal area is the interface between the marine and terrestrial environments exposed to daily tides and to extremely dynamic events with different spatial and temporal scales
As the risk of image saturation by sun glint effects is too high on the intertidal zone, preliminary tests were made on the identification of the improvement using the sun glint correction [60]
The approach is based on the temporal variability of the near infrared spectral reflectance on the intertidal zone and the correlation with tide height

Summary

Introduction

The intertidal area is the interface between the marine and terrestrial environments exposed to daily tides and to extremely dynamic events with different spatial and temporal scales. LIDAR systems measure depths regularly up to 40 m with accuracy of 10–30 cm [15] These systems are very useful in shallow waters with reefs or where large ships are excluded but are only appropriate for bathymetric mapping over relatively small geographical areas [15,16]. In order to improve bathymetric models in areas where hydrographic information is sparse or outdated or high dynamic areas where in situ measurements are too expensive, remote sensing techniques are emerging as a strong solution [17]. With improved synoptic vision and high spatial and temporal resolution of Earth observation satellites, such as Sentinel-2, new techniques for coastal monitoring and bathymetry extraction are emerging [23,24,25,26]

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