Experiments for multibeam Backscatter Adjustments on the NOAA Ship FAIRWEATHER

A series of experiments were conducted to adjust and normalize the acoustic backscatter acquired by Reson 8111 and 8160 systems. The dependency of the backscatter on the receiver gain, transmit power, pulse width and acquisition mode was analyzed. Empirical beam patterns are calculated as the difference between the backscatter measured by the sonars and the expected backscatter. Expected acoustic backscatter is estimated based on a mathematical model

Geocoder: An Efficient Backscatter Map Constructor

The acoustic backscatter acquired by multibeam and sidescan sonars carries important information about the seafloor morphology and physical properties, providing valuable data to aid the difficult task of seafloor characterization, and important auxiliary information for a bathymetric survey. One necessary step towards this characterization is the assemblage of more consistent and more accurate mosaics of acoustic backscatter. For that, it is necessary to radiometrically correct the backscatter intensities registered by these sonars, to geometrically correct and position each acoustic sample in a projection coordinate system and to interpolate properly the intensity values into a final backscatter map. Geocoder is a software tool that implements the ideas discussed above. Initially, the original backscatter time series registered by the sonar is corrected for angle varying gains, for beam pattern and filtered for speckle removal. All samples of the time series are preserved during all the operations, ensuring that the full data resolution is used for the final mosaicking. The time serie s is then slant-range corrected based on a bathymetric model, in the case of sidescan, or based on beam bathymetry, in the case of the multibeam. Subsequently, each backscatter sample of the series is geocoded in a projected coordinate system in accordance to an interpolation scheme that resembles the acquisition geometry. An anti-aliasing algorithm is applied in parallel to the mosaicking procedure, which allows the assemblage of mosaics at any required resolution. Overlap among parallel lines is resolved by a priority table based on the distance of each sample from the ship track; a blending algorithm is applied to minimize the seams between overlapping lines. The final mosaic exhibits low noise, few artifacts, reduced seams between parallel acquisition lines and reduced clutter in the near-nadir region, while still preserving regional data continuity and local seafloor features

Clustering Acoustic Backscatter in the Angular Response Space

Backscatter mosaicking is a necessary step in the analysis and interpretation of sidescan and multibeam sonar records. However, due to limitations intrinsic to the mosaicking technique, backscatter mosaics are restricted in their capacity to unambiguously discriminate seafloor properties. A more adequate technique to characterize the seafloor is the analysis of backscatter angular responses, since those responses are intrinsic properties of the seafloor. This technique sometimes lacks spatial resolution, however, as the analysis is limited to the swath width of the sonar. In this paper, we propose an approach to combine mosaicking and angular response analysis techniques in an attempt to take advantage of both the spatial resolution of the mosaic, and the angular resolution derived from the angular response analysis. In order to test these ideas, we used acoustic backscatter acquired by a Reson 8101 (240kHz) multibeam sonar during normal survey operations conducted on the NOAA Ship FAIRWEATHER around Cape Decision, Alaska in spring 2005. First, we defined parameters that uniquely described the angular responses, and treated those parameters as a feature vector in a multidimensional space. The parameters were then clustered with a simple unsupervised clustering algorithm. The result of the clustering analysis defined areas on the seafloor which had similar angular responses, which we called themes. We then used these themes to develop more robust indicators of angular response from their coverage areas, which were finally used as Angle Varying Gain correction tables to assemble an enhanced mosaic

Automatic Estimation of the Seafloor Geomorphology of the Santos Basin, Brazil

The bathymetry and acoustic backscatter of Santos Basin, Brazil were mapped using a SeaBeam 2112 (12 kHz, 151 beam) Multibeam Echosounder (MBES) aboard the R/V Falcon Explorer. This MBES data was acquired from January-November, 2000, during a high-resolution multi-channel 3D seismic survey, resulting in 380 parallel lines of 90 km length, spaced 250 m apart. The final survey mapped an area of 5,000 km${}^2$ in water depths of 900--2000 m. These closely spaced multibeam tracks resulted in an average overlap between swaths of 1000%, thereby ensonifying most areas of the seafloor at least ten times. Traditional (hand) processing of a dataset this dense is time-consuming and tedious, and is prone to subjective decisions and operator fatigue. However, the density of the survey makes it ideal for automatic processing methods. Recently, we have developed an algorithm called CUBE that addresses the twin concerns of robustness and reliability that are often raised about automatic processing methods. Based on a very robust multiple hypothesis Bayesian estimator, CUBE processes MBES bathymetry directly into a set of gridded products representing the best estimate of probable depth, and a measure of the uncertainty associated with this estimate. We apply CUBE to the Santos Basin data, illustrating in terms of processing time and human effort the advantages of processing such data automatically. We compare the automatically generated data with a hand-processed set, showing that the results agree to within the estimated experimental uncertainty. We next illustrate the use of CUBE as a data quality measure, indicating areas of concern in the data. Finally, we utilize the bathymetric grid resulting from CUBE to investigate the seafloor morphology, which includes a set of linear depressions parallel and perpendicular to the Shelf break. These linear depressions are the surface expression of fault planes related to subsurface salt walls. In the shallowest part, the detailed bathymetry also shows various pockmarks (350 m wide) possibly associated with fluid expulsion, while in the deeper portion we observe a small number of larger ones (2500 m wide), which are clearly inactive as they are partially filled with recent sediments. Some pockmarks are aligned with fault planes, suggesting a preferential pathway for fluid expulsion. The acquisition geometry for this survey allowed us to analyze the behavior of the backscatter response as a function of grazing angle for any given piece of seafloor, thus eliminating the need to assume a homogeneous seafloor across the swath. Although the backscatter is not calibrated, the variation in response can be used to investigate the effects of gas in shallow sediments of the survey area

Cuban Military Culture

The Revolutionary Armed forces (Fuerzas Armadas Revolucionarias—FAR) have traditionally been the most powerful official institution in Cuba and the central pillar sustaining the communist regime. Beginning with the stunning victory against an American sponsored exile invasion at the Bay of Pigs, the Cuban military became one of the best and most experienced fighting forces of any small nation. This report examines how traditional FAR culture has been characterized by exalted status, confidence, high morale, strict discipline, belief in the leadership of the Castro brothers, and an assertive nationalism antagonistic towards the United States. However, today, it is about a tenth of its previous maximum strength and faces an uncertain future.https://digitalcommons.fiu.edu/jgi_research/1020/thumbnail.jp

Making the Grade: What\u27s Motivating China\u27s Educational Outreach in LAC?

This paper considers the multiple motivations for China’s educational outreach in the region, drawing from Chinese policy and analysis and many dozens of examples of academic linkages forged between China and Latin America and the Caribbean in recent years. Whether initiated by Chinese or LAC institutions, these programs are an increasingly central feature of China-LAC relations, a part of the extension of China’s BRI to LAC, and a useful measure of China’s varied and evolving interests throughout the region.https://digitalcommons.fiu.edu/jgi_research/1049/thumbnail.jp

United States Policy in the Hemisphere: Influencing the State and Beyond

United States—Latin American and Caribbean (LAC) relations are strong, and more importantly, built on a broad base of sophisticated, organic relationships that extend well beyond state-to-state engagements. Furthermore, U.S.-LAC relations encompass far more than what is often covered in the commentariat—like the number of presidential visits, the emergence of extra-hemispheric actors, problems related to drugs and immigration, or when compared to the visibility of U.S. engagements in others parts of the world. These outdated measures fail to truly appreciate the complexity and depth of U.S.-LAC relations today, all of which are the result of our persistent and deliberate engagement with the Americas.https://digitalcommons.fiu.edu/jgi_research/1029/thumbnail.jp

Domestic Politics in the Dominican Republic after the Earthquake in Haiti

Despite historical tensions between the Dominican Republic and Haiti, Dominicans appear to have put aside their resentment in favor of supporting Haitians after the earthquake that devastated the neighbor nation in January 2010. Over the past several months, there has been unprecedented cooperation between the Dominican Republic and Haiti, with little evidence of a negative impact on domestic politics in the Dominican Republic. In fact, the high ratings of President Leonel Fernández and the results of the May Parliamentary elections may suggest that how the Fernández administration handled the Haitian crisis did not have a negative impact on citizens’ perception. However, the issue of Haitian immigration remains very sensitive in the Dominican Republic, and has the potential to become the major concern on the domestic political front. As of June 2010, the Haitian crisis seemed to have little or no impact on Dominican politics, as the following points indicate: The May 16, 2010 Parliamentary elections increased President Fernández political party to 31 out of 32 Senate seats, and 105 out of 183 Chamber of Deputies seats; this is a total increase of 18 seats from the previous term. Polls indicate that President Fernández has a 54 percent approval rating. Polls also indicate that Haiti is not among the most pressing issues of concern to Dominican citizens. Instead, 65 percent of the population identifies drug trafficking and corruption as the greatest concerns. The immigration debate will remain the major consideration in domestic politics in the Dominican Republic; 62.4 percent of Dominicans polled think that the military should be strengthened along the DR-Haitian border

The Future of US-Colombia Relations

Colombia has been one of the United States’ closest allies in the region, stretching back to the 1950s. Colombia was the only Latin American country to join the Korean War in a direct military role. In 1951, the first 1,000 Colombian soldiers disembarked in South Korea where they maintained a military presence until the end of the war. During the 1960s and 1970s, Colombia became one of the largest recipients of United States assistance in Latin America. The assistance was designed to enable Colombia to develop economically through industrialization, agrarian, and social reforms and helped solidify Colombian-U.S. military relations.1 Colombia’s support of the United States during the war and the U.S.’ economic support of Colombia during the 1960s and 1970s fostered a multi-faceted, long-lasting diplomatic and military relationship between the two countries that has evolved, but remained strong for over half a century.https://digitalcommons.fiu.edu/jgi_research/1006/thumbnail.jp