Underwater Acoustic Source Localization

Underwater Acoustic Source Localizationbutton4

By: Mad Helmi Bin Ab. Majid (PhD Student)

 

 

Target localization is a branch of underwater localization research which related to the study of how to determine position of underwater target of interest with respect to a known reference point. Global positioning system (GPS) has been used for decades to determine position located on the ground by using multilateration principles from multiples satellites. Unfortunately, GPS unable to work in underwater environment due to poor penetration of radio signal. Luckily, acoustic signal travel well within the water column with speed of approximately 1500 m/s which is about four times faster than speed on the surface. Underwater acoustic pinger localization is one of the research topic related to the underwater localization. The working principle of the acoustic source localization is shown in the following figure. From the figure, three different phenomena of acoustic source localization could be observed:

  1. Firstly, absolute localization of the stationary target directly from surface vessel. In this case, all measurement taken or estimate with respect to position of the surface vessel based on acoustic signaling. Since position of the vessel is determined by the GPS, absolute position of the pinger source could be determined.
  2. Secondly, absolute localization of mobile acoustic target (in this case underwater vehicle) is performed directly form surface vessel based acoustic signaling. The only difference from the previous phenomena is the acoustic pinger is carried by underwater vehicle which is considered as mobile acoustic source.
  3. Thirdly, relative localization of the stationary target with respect to the position of the underwater vehicle. At this stage, this localization is considered relative since the underwater vehicle does not carry any GPS receiver. However, since underwater vehicle itself is localized by surface vessel through underwater acoustic positioning, the absolute positioning could be obtained. This method of localization is commonly used for deep water application where variation of sound speed and water depth is significant.

4a nov15

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