# Aquasafe: A Remote Sensing, Web-Based Platform for the Support of Precision Fish Farming
## 2 Materials and Methods
### Parameters
#### 2.3.1 Water Quality Parameters  
The satellite data and information acquired from the Copernicus Marine Environment Monitoring Service (CMEMS) and Sentinel missions were used to achieve a comprehensive understanding of ocean dynamics and estimate the water quality parameters (Figure 1b). To ensure the highest accuracy of our estimates, we performed recommended preprocessing and data correction procedures, as well as an interpolation technique to further enhance the resolution and detail of the information (Figure 2). Chlorophyll-a (chl-a): Satellite data are widely used for the detection of optically active parameters such as chlorophyll-a (chl-a), total suspended matter, and temperature. Parameters described as \"optically active\" affect the optical properties of water at specific wavelengths, causing alteration to the color of the water and consequently to the reflectance values of the satellite images. Satellites Sentinel-2 (MSI) and Sentinel-3 (OLCI) are widely assumed to provide reliable information about concentrations of chlorophyll-a with algorithms based on the inherent optical properties of water bodies. More specifically, the algorithm Case 2 Regional Coast Color (C2 RCC) was first developed from [PERSON] and [PERSON] (2007) [PERSON] and [PERSON] (2007) and, after several improvements, is now applicable to all current ocean color sensors, including Sentinel-2 MSI and Sentinel-3 OLCI [21] (currently supported sen  
Figure 2: The input satellite and CMEMS data were preprocessed and used to estimate the relevant water quality parameters. sors include MERIS, OLCI, MODIS, VIIIRS, SeaWiFS, OLI, and MSI). C2 RCC is based on an extended database of simulated water leaving reflectances and related top-of-atmosphere radiances. The processor includes two parts, the atmospheric correction part and the in-water part. The main input in the atmospheric part is the top-of-atmosphere reflectance, and the main output is the directional water leaving reflectance. The in-water modeling is performed using the Hydrolight model and uses as input the atmospherically corrected reflectances. After excluding the outliers, the inherent optical properties of the water (IOPs) are estimated and transmitted to the forward model. The IOPs are then transformed to chlorophyll-a concentration and total suspended matter [21]. Sea Surface Temperature (SST): Sea surface temperature (SST) data have already been processed to Level-2 by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) at a resolution of 1 km and are used for further analysis. According to Sentinel-3 SLSTR User Guide, SST measurement is obtained through a highly accurate calibration of the three infrared channels at 3.74, 10.85, and 12 \(\mu\)m (S7-S8-S9), which are used to correct for water vapor atmospheric absorption (split window during day and triple window during night) and observing the same on-ground pixel through two atmospheric path views for correction of aerosol effects. It is important to note that SLSTR returns SST measurements for the ocean \"skin\". Because thermal infrared radiation does not penetrate far into the water column, the infrared radiometric temperature is only that of the top few tens of micrometers. The temperature of the sea skin surface is typically a few tenths of a degree cooler than the temperature a few centimeters below. Oceanographically, SST is considered a measure of the temperature in the top 10 cm. Dissolved Oxygen (DO): Dissolved oxygen is not included in the optically active parameters; therefore, it is unlikely to measure its concentration directly from the reflection values of satellite sensors. However, research has shown that it can be estimated indirectly because of its correlation with other parameters, such as temperature and chl-a [22; 23]. Based on this relation, the concentration of dissolved oxygen was estimated using regression analysis and multisource data [19].