537
configurations. The user must choose the polarization configuration, the incidence
angle, and the spatial resolution associated with the chosen imaging mode.
Combined approaches of using optical and microwave images can improve the vegetation analysis.
Airborne laser instruments such as LiDAR represent innovative tools for management applications, including flood zone delineation, monitoring beach nourishment projects, and mapping vegetation (Niculescu et al. 2016) and changes along
sandy coasts and shallow benthic environments due to storms or long-term sedimentary processes (Klemas 2013). Identifying potential restoration sites and prioritizing them using ecological and economic criteria is by no means a simple task
(Russell et al. 1997; Thayer 1992; White and Fennessy 2005). The combined use of
LIDAR, radar, and multispectral imagery can improve the accuracy of monitoring
vegetation species discrimination and provide a better understanding of the topography/bathymetry and hydrologic conditions.
17.7.2 Dataset
We used the following satellite images in this study: 20 Sentinel-1 images acquired
between 9.10.2014 and 01.04.2016 (Table 17.2) and one Sentinel-2 image acquired
on 28.04.2016 in the restored areas in the northern part of the delta (Babina and
Cernovca). The Sentinel-1 data were acquired in a time series that covered the entire
growth season of 2015 and part of 2016. This enabled us to determine the influence
of the time dimension and of the polarimetric dimension (VV and VH polarization
are available) on the characterization and classification of the vegetation in the
restored delta areas.
Since it was first launched in April 2014, the Sentinel-1 satellite has allowed
specialists to monitor the earth’s surface day and night regardless of weather conditions and has transmitted high-resolution space images free of charge. The Sentinel
1 SAR mission is part of the Copernicus Programme – European Earth Observation
Programme, which was previously called GMES (Global Monitoring for
Environment and Security), of the European Space Agency. Placed on an orbit at an
altitude of 693 km, Sentinel-1 operates in four data collection modes: the StripMap
(SM) mode, the Interferometric Wide swath (IW) mode, the Extra-Wide swath
(EW) mode and the Wave (WV) mode. Each mode provides different products with
respect to spatial resolution and imaging swath. Sentinel-1 images are captured in C
band (5.5 cm), and they may exhibit simple HH or VV polarization or double
HH+HV or VH +VV polarization. The data used in our research were collected in
the IW mode. This mode includes three sub-swaths, namely IW1, IW2 and IW3,
which correspond to cyclical antenna deviations. This mode provides GRD (Ground
Range Multilook Detected) and SLC (Single Look Complex) images made up of
three IW. The GRD images are Multilook images (five looks for the IW mode) with
less speckle noise and coarser space resolution. Although the SLC products have
finer resolution, it is difficult to use them directly due to the phase information,
17 Alteration and Remediation of Coastal Wetland Ecosystems in the Danube Delta…
configurations. The user must choose the polarization configuration, the incidence
angle, and the spatial resolution associated with the chosen imaging mode.
Combined approaches of using optical and microwave images can improve the vegetation analysis.
Airborne laser instruments such as LiDAR represent innovative tools for management applications, including flood zone delineation, monitoring beach nourishment projects, and mapping vegetation (Niculescu et al. 2016) and changes along
sandy coasts and shallow benthic environments due to storms or long-term sedimentary processes (Klemas 2013). Identifying potential restoration sites and prioritizing them using ecological and economic criteria is by no means a simple task
(Russell et al. 1997; Thayer 1992; White and Fennessy 2005). The combined use of
LIDAR, radar, and multispectral imagery can improve the accuracy of monitoring
vegetation species discrimination and provide a better understanding of the topography/bathymetry and hydrologic conditions.
17.7.2 Dataset
We used the following satellite images in this study: 20 Sentinel-1 images acquired
between 9.10.2014 and 01.04.2016 (Table 17.2) and one Sentinel-2 image acquired
on 28.04.2016 in the restored areas in the northern part of the delta (Babina and
Cernovca). The Sentinel-1 data were acquired in a time series that covered the entire
growth season of 2015 and part of 2016. This enabled us to determine the influence
of the time dimension and of the polarimetric dimension (VV and VH polarization
are available) on the characterization and classification of the vegetation in the
restored delta areas.
Since it was first launched in April 2014, the Sentinel-1 satellite has allowed
specialists to monitor the earth’s surface day and night regardless of weather conditions and has transmitted high-resolution space images free of charge. The Sentinel
1 SAR mission is part of the Copernicus Programme – European Earth Observation
Programme, which was previously called GMES (Global Monitoring for
Environment and Security), of the European Space Agency. Placed on an orbit at an
altitude of 693 km, Sentinel-1 operates in four data collection modes: the StripMap
(SM) mode, the Interferometric Wide swath (IW) mode, the Extra-Wide swath
(EW) mode and the Wave (WV) mode. Each mode provides different products with
respect to spatial resolution and imaging swath. Sentinel-1 images are captured in C
band (5.5 cm), and they may exhibit simple HH or VV polarization or double
HH+HV or VH +VV polarization. The data used in our research were collected in
the IW mode. This mode includes three sub-swaths, namely IW1, IW2 and IW3,
which correspond to cyclical antenna deviations. This mode provides GRD (Ground
Range Multilook Detected) and SLC (Single Look Complex) images made up of
three IW. The GRD images are Multilook images (five looks for the IW mode) with
less speckle noise and coarser space resolution. Although the SLC products have
finer resolution, it is difficult to use them directly due to the phase information,
17 Alteration and Remediation of Coastal Wetland Ecosystems in the Danube Delta…