*3.2.1 In-situ data*

To collect field data from the study area for calibration with remote sensing data, field measurements were performed on April 7, 2019, at the same time as the Landsat-8 satellite passed the study area at 6:37 UTC. On the day of sampling, the sea level was at the highest water level and without wave turbulence. For this purpose, immediately after collecting the water sample using special bottles, the location of each station was determined using a GPS device. A total of 10 stations were located and sampled. The sampling started from the area between the entrance of the estuary and ended at the exit of the estuary leading to the high seas and lasted about 1 hour. **Figure 3** shows the field operation. In the laboratory, water samples were transferred to tubes containing 10 ml of ethanol and then centrifuged at 2500 rpm for 5 minutes and decomposed in the absorption range of 664 and 665 nm using a spectrophotometer. Finally, the field chlorophyll of each station was calculated using Eq. 1.

$$\text{Chlla}\_{\left(^{\text{asy}}\text{m}^{3}\right)} = \frac{2\mathfrak{G}.7 \times \left(\mathfrak{G}\mathfrak{G}\mathfrak{A}\_{\text{b}} - \mathfrak{G}\mathfrak{G}\mathfrak{S}\_{\text{a}}\right) \times \text{V}\_{\text{ext}}}{\text{V}\_{\text{sau}} \times \text{L}} \tag{1}$$

Where 665a and 664b, respectively, before and after acidification of the samples in the spectral range, Vext amount of extraction per liter unit, Vsam amount of sample per cubic meter, L light path of the sample tube per unit centimeter and Chla chlorophyll concentration per mg unit Cubic meters.

#### *3.2.2 Remote sensing data*

In this study, Landsat-8 satellite images were used to estimate chlorophyll-A concentration. Landsat-8 is one of the newest multispectral satellites launched on February 11, 2013 to monitor natural resources. This satellite has a spatial resolution of 30 meters, 11 Multispectral bands (in the range: visible, reflective infrared and thermal infrared) and its review period from Earth is 16 days. **Table 1** shows the details of Landsat-8 time series data for estimating chlorophyll-A concentration are presented.

**Figure 3.** *Field operations in the study area.*

*Application of Remote Sensing in Natural Sciences DOI: http://dx.doi.org/10.5772/intechopen.94468*


**Table 1.**

*Specifications of time series data used.*
