**4. Sensors and satellites**

In coastal region monitoring, oil spill detection and its removal play an important role in protecting the environment and reducing economic loss. It could be achieved through remote sensing technique that uses space-borne satellites and airborne aircrafts. The space-borne satellites use mounted RADAR in it which comprises sensors. It is also observed that the selection of particular sensor plays an important role in detecting oil spills. At the initial level, space-borne satellites are most suitable for oil spill detection but further analysis could be carried out using aircraft sensors [6]. In ocean monitoring, microwave sensors are preferred to optical sensors due to its excellent performance under all weather conditions. The role of different sensors in oil spill detection is presented in the subsequent section.

At the initial stage oil slicks have been identified and processed using images of ERS, ENVISAT ASAR, and RADARSAT-1. Recently, many radar satellites with a potential for oil slick location have been propelled, specifically, RADARSAT-2, Terra-SAR-X, and COSMO SkyMed. A general exchange of the suitability of RADARSAT-2 for beach-front applications is found in [17]. These satellite radars use new imaging modes that open some new potential outcomes for enhanced imaging of oil slicks.

However, the ERS-1 is currently being used by the Norwegian Space Center (NSC) on behalf of pollution control board in the coastal region for oil spill detection. In ERS-1, radar frequency range is located accurately and it is used for processing radar signal-by-signal projections. It is the technique used to capture images of resolution 30 m X 30 m. In ERS-1 SAR raw data processing, large geographical area can be covered by adjusting physical length of the ERS-1radar antenna. In specific, for oil spill detection, the ERS-1 radar produces variety of images at various levels based on wind speed by covering large area. These images need to be processed to identify oil slicks. At present, ENVISAT RADAR is predominantly used for oil spill detection due to its wide area coverage with a spatial resolution of 150 m and a pixel spacing of 75 m. Similarly, the RADARSAT, ScanSAR covers 60–400 km swath width with a spatial determination of 50 m and a pixel dispersing of 25 m [25].

*Computational Techniques of Oil Spill Detection in Synthetic Aperture Radar Data: Review Cases DOI: http://dx.doi.org/10.5772/intechopen.108115*

Even though the ENVISAT higher-frequency radar, spatial data determination is accessible from the remote sensing medium determination, the spatial data information takes care a sensible bargain permitting covering the vast territories and as yet recognizing significantly littler oil slicks from the SAR image regions [26].

The other is named as COSMO-SkyMed satellite with a group four, which permits the great scope of feature analysis in significant time periods. The COSMO-SkyMed SAR fragment was dispatched in November 5th, 2010 at 1920 L and it has been utilized for the water/deep-water horizon oil slick studies. As indicated in [27], it ought to have greater capability in detecting oil slick localities with double polarimetry SAR images that are captured by COSMO-SkyMed satellite sensors.

Terra-SAR-X has the capability of capturing images in different directions while monitoring the specified area of coastal region. It uses larger value of standard deviation for differentiating oil slick or look-alike. In addition, it uses double polarimetric SAR technique, in discriminating the spilled oil from look-alike. The RADARSAT-2 has a few polarization alternatives—for example, single-polarization SAR modes with one of the accompanying polarizations such as HH or HV or VH or VV [28]. It also offers dual polarization SAR modes with appropriate polarizations such as HH + HV or VV + VH. A quad-pol alternative is likewise feasible for fine and standard modes.

Adamo et al. have proposed a model for oil spill examination by considering normal number of accessible MODIS, MERIS, and ASAR images. These images need to be captured within observing time periods without cloud images in sunglint conditions. However, the MODIS/MERIS is ensured if the smoothness of radar data as image is situated in oceanography regions inside as well as outside. Similarly, they noticed a wavelength from reliance oil/non-oil class distinctness with expanded execution at



#### **Table 3.**

*Different space-borne satellites with its specifications for remote sensing.*

the more NIR band wavelengths of MODIS and MERIS [27–29]. Their recreations for a range in the Mediterranean appeared that by and large 150 images every year would be suitable if an aggregate cloud list of under 2/10 was required. Occasional varieties further demonstrated that the period between spring and pre-winter was the most suitable for sunglint conditions. MERIS and MODIS symbolism is routinely used to make water quality maps and checking algal sprouts [30]. Indeed, without sunglint conditions, algal blossom maps can be utilized in the mix with SAR pictures to lessen the quantity of false cautions because of green growth. Radar satellites are most suitable for quick detection and monitoring of large areas. At present, most of the remote sensors can detect oil spills.

**Table 3** shows various satellite-based sensors for oil spill monitoring. From these satellites, sensors are using various spectral bands (i.e., X, L, C, and Ku-band) for monitoring the coastal region surfaces. Finally, the remote sensing manner transmits the data from one location to another location, while observing the ocean surfaces for change detection of costal activities.


#### **Table 4.**

*Different band and its wavelength with its frequency range.*

*Computational Techniques of Oil Spill Detection in Synthetic Aperture Radar Data: Review Cases DOI: http://dx.doi.org/10.5772/intechopen.108115*

In **Table 4**, different bands used by different satellites are shown below with its frequency range and its wavelength. It can be considered as for the satellite band type as well as the frequency and wavelength ranges. The corresponding radar satellite only uses these appropriate band models. And also, most of the radar satellites are using a C or X-band for the coastal region monitoring.
