|
Underwater navigation is the common reference term for navigation techniques learned by Scuba divers in order to navigate in an underwater environment. Although it is considered a basic skill, it is normally only taught to a limited degree as part of basic Open Water certification. Most North American diver training agencies only teach significant elements of underwater navigation as part of the Advanced Open Water Diver certification program. Underwater navigation is usually a core component of most, if not all, advanced diver training. In the PADI Advanced Open Water Diver course, it is one of the two mandatory skills (together with Deep diving) which must be taken alongside three elective skills.〔http://www.padi.com/padi/en/kd/advancedopenwater.aspx〕 Training agencies promote underwater navigation as a skill (despite the fact that it is less popular than other recreational diving specialties) on the basis that it: * builds diver confidence * saves energy by minimising excess swimming * makes dive planning more effective * keeps dive buddies together * reduces air consumption Underwater navigation is a component of the scuba-based underwater sport, underwater orienteering.〔(【引用サイトリンク】title=CMAS - Orienteering )〕 ==Navigation techniques== Underwater navigation in recreational diving is broadly split into two categories. ''Natural navigation'' techniques, and ''orienteering'', which is navigation focused upon the use of an underwater magnetic compass. Natural navigation, sometimes known as pilotage, involves orienting by naturally observable phenomena, such as sunlight, water movement, bottom composition (for example, sand ripples run parallel to the direction of the wave front, which tends to run parallel to the shore), bottom contour and noise. Although natural navigation is taught on courses, developing the skills is generally more a matter of experience. Orienteering, or compass navigation, is a matter of training, practice and familiarity with the use of underwater compasses, combined with various techniques for reckoning distance underwater, including kick cycles (one complete upward and downward sweep of a kick), time, air consumption and occasionally by actual measurement. Kick cycles depend on the diver's finning technique and equipment, but are generally more reliable than time, which is critically dependent on speed, or air consumption, which is critically depencant on depth, work rate, diver fitness, and equipment drag. Techniques for direct measurement also vary, from the use of calibrated distance lines or surveyor's tape measures, to a mechanism like an impeller log, to pacing off the distance alond the bottom with the arms. Many skilled underwater navigators use techniques from both of these categories in a seamless combination, using the compass to navigate between landmarks over longer distances and in poor visibility, while making use of the generic oceanographic indicators to help stay on course and as a check that there is no mistake with the bearing, and then recognising landmarks and using them with the remembered topography of a familiar site to confirm position. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Underwater navigation」の詳細全文を読む スポンサード リンク
|