English: Data Screen of a DS-3 diver navigation and observation recording terminal, part of an AquaMap Long Baseline (LBL) acoustic positioning system. The grid is 10m x 10m. The diver is at location (A), and has selected the site of a previous diver observation (B) as the next destination. The identifier of that point 'wp4' along with its current distance and bearing is shown in window (C). The small blue crosshairs form the position track of the diver, and overlaid at several locations (D) we see the green diamond symbol indicating observations recorded along the way. The position of baseline transponders (E), which are the references for navigation equivalent to the satellites in a GPS system, are shown by their number and a green square. The diver position window (F) can show geo-referenced UTM coordinates or, in this case, baseline relative coordinates. The system also includes the estimated position error by evaluating the 'range circles' for the multiple baseline stations. In the ideal case, all circles would meet precisely at one point, which is the location of the diver. In reality, measurement errors caused by a combination of environmental, setup and system factors puts a limit on accuracy. In this example, the estimated error is 0.235m.