positions. They are often accompanied by pingers, small transponders that can be detected by an underwater acoustic positioning transducer which allows a pinging vessel or the node vessel itself to establish a definite sea floor position for each node on deployment. Depending on the contract, pingers can be located on every node or every third node, for example. Pinging and pinging equipment is the industry shorthand for the use of USBL or Ultra-short baseline acoustic positioning systems which are interfaced with vessel based differential GPS or Differential Global Positioning System navigation equipment.