# Experimental Design of a Mobile Landing Platform to Assist Aerial Surveys in Fluvial Environments
## 2 State of the Art  
Unmanned maritime systems can be divided into two categories: underwater vehicles and surface vehicles [9]. Unmanned underwater vehicles (UUV) [10] are probably the best known and used in robotic applications. The prototype described in this article is an unmanned surface maritime system or USV.  
Furthermore, most of the USV research found in the last decade falls into two configurations: double-hulled ([11]), and mono-hull ([12; 13]). The configuration most used in research is the double-hull configuration, e.g., catamaran. In this work the double-hull design was adopted mainly due to the increased stability, available area to include a landing base, the ability to make quick 360\({}^{\rm o}\) turns, and because it can be operated closer to the shore.  
The idea of mobile maritime landing platforms arose from the concept of reusable space rockets, for which autonomous landing controllers were developed [14]. These platforms can position themselves under adverse weather conditions, with an accuracy of \(+/-3\) m. The design of a landing base for UAVs that fly over fluvial environments was inspired in this project.  
The previous works found employing double-hull platforms focus in developing robust modeling and control approaches to improve the vehicles autonomous navigation [11; 15; 16]. In these works, the USV employed are off-the-shelf vehicles that have not being built from the scratch. Therefore, there is less decision-making in the designing, fabrication and mechatronics setup of the vehicle as enhanced in the present work.  
Moreover, the USVs employed in previous works have physical characteristics that make their mobility to the survey sites difficult or even impossible. Since most of the times these areas are found in unstructured environments, such as alpines lakes or ponds. The proposed work goal is to achieve maximum lengths under 1 m and less than 5 Kg of mass.  
Orchestration behaviors applying the COLREGs rules (from the International Maritime Organization (IMO)) were also tested in multiple double-hull vehicles [17]. The authors implemented several path planning approaches in three double-hull USV where the control performance was also evaluated in a real environment. This research focus in developing autonomous navigation approaches for USV that will operate in the sea which is not the operations domain addressed by the platform presented in this manuscript  
When it comes to the idea of having an autonomous landing platform over a maritime environment there are not many works introducing such systems. A software and hardware architecture is presented to allow a helicopter to perform takeoff and landing maneuvers on a double-hulled USV equipped with a landing base [18]. In this document, the authors describe the techniques used but omit the result, which is limited to a conceptual analysis of the findings.  
Finally, in [PERSON] et al. [19] a symbiosis between a catamaran and a hexacopter is presented. The catamaran worked as a landing base, equipped with a laser scanner, a sonar for underwater obstacles detection, a multiple vision system and a structure capable of transporting people. The hexacopter overflows the catamaran position, complementing the aerial perspective. Thus, through both platforms, a 3D map of the terrain was reconstructed with a very accurate landscape vision. For the best of our knowledge this work is the one that gets closer to the idea proposed in this manuscript. However, in the previous work the budget and platform size was not a restriction. This off-the-shelf 4.5 m long USV counts with advanced navigation and perception sensors which suggest high development costs.  
Our aim is that this vehicle supports small USVs remote sensing in fluvial environments, which are easy to replicate, portable, and have an affordable market price (most of the vessels referenced in the literature for which data is available have prices above the thousand euros mark). Figure 1 illustrates a possible scenario where the proposed system can be used.