# Ocean Remote Sensing Techniques and Applications: A Review (Part II)
## 2 RS Applications in Ocean
### Iceberg
#### 2.1.1 Optical  
As mentioned in Table 1, optical satellites are considerably beneficial for iceberg mapping and monitoring due to the availability of high-resolution images and the simplicity of iceberg visualization. However, atmospheric conditions, cloud-prone possibility, and the lack of reflected solar radiation, especially in the winters in Arctic regions, are the main limitations of these systems [21]. Generally, floating icebergs have bright sharp boundaries when compared with dark open water, making them easily distinguishable [33]. Furthermore, when other features (i.e., boats, islands, and ships) exist in the imagery, the red and NIR bands could be used to compute the redness index for discriminating these features [27]. For instance, it has been reported that icebergs had redness values between 0.3 and 0.45, while ships were in the range of 0.45 and 0.6 [27]. Both airborne and spaceborne optical satellite images have been extensively applied to detect and monitor icebergs in the Arctic and Antarctic regions [22; 33; 34]. For instance, [PERSON] et al. (2018) investigated the efficiency of aerial photogrammetry for iceberg deterioration estimation. To this end, the Structure-from-Motion (SfM) and deterioration \begin{table}
\begin{tabular}{c c c c} \hline \hline
**RS System** & **RS System (Type)** & **Advantage** & **Disadvantage** \\ \hline Passive & Optical & High spatial resolution and relatively simple to visualize and identify icebergs & Atmospheric condition, subject to cloud cover, and lack of solar radiation in polar regions \\  & SAR & Provide all-weather data with a high spatial resolution & Narrow swath and incidence angle dependencies \\  & Scatterometer & All-weather data acquisition & Coarse spatial revolution \\  & & Can be employed for automatic and simple identification of icebergs based on their signature on waveform echo & Relatively coarse spatial resolution, requires high caution in SI prone areas \\  & HF radar & Large-scale area coverage, high spatial resolution, cost effective & Lack of data availability due to the limited number of HF radars \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Different RS systems for iceberg studies along with their advantages and disadvantages. Figure 2: An example of iceberg in satellite imagery: (**a**) A 300 square kilometer iceberg spawned from the Pine Island Glacier captured by the Sentinel-2 optical image (ESA, n.d.), and (**b**) Sentinel-1 SAR data acquired over parts of the Pine Island Glacier and Thwaite Glacier (ESA, n.d.). detection threshold algorithms were combined to calculate the masses of two icebergs. The authors recommended developing more sophisticated algorithms based on SfM because it provided promising results for the iceberg's mass estimation. Additionally, [PERSON] and [PERSON] [33] employed very high-resolution Worldview-2 optical images to create a comprehensive calving iceberg inventory (i.e., population, size distribution, and area-volume scaling) of the San Quintin glacier in Chile. They used the multiresolution segmentation algorithm and the Random Forest (RF) classifier to identify icebergs. Various contextual information along with the watershed algorithm were applied to enhance the performance of the proposed approach, enabling the detection of 3184 out of 3212 icebergs. In another study, [PERSON] [27] compared the application of Convolutional Neural Networks (CNN) and Support Vector Machine (SVM) for iceberg-ship classification. The results indicated the higher accuracy of the CNN approach compared to other methods. Several sophisticated algorithms, including the Cross-correlation in the frequency domain on orientation images [35] and the Normalized Cross-Correlation (NCC) [36], have also been introduced to track and estimate the velocity of drifting icebergs. For example, [PERSON] et al. [28] developed a novel rotation-invariant feature tracking approach to estimate the ice velocity fluctuations from 2004 to 2015 in East Antarctica.