The underwater GPS problem

Abstract

Fig. 1. An underwater positioning system (left), a desktop experiment (middle), and a GPS error budget from Wikipedia (right). Abstract-It is well known that the ordinary Global PositioningSystem (GPS) fails to provide location and time information under water. The reason is that the electromagnetic signals from the orbiting satellites are heavily damped in water and hence can not be detected by the receiver in most cases of interest. Acoustic waves are the canonical alternative, and there exist a variety of acoustically based systems.It is important to estimate the accuracy of position estimates and if possible correct for the errors. This is done systematically in the GPS case by the concept of Dilution Of Precision (DOP), and is also the natural approach underwater. The main issue presented below is a discussion and analysis of the concept of DOP in the context of Underwater Positioning Systems (UPS). This includes statistical models that differ from the one canonically used. Some of the sources of errors in the UPS case differs substantially from the GPS case. It is in particular demonstrated that the maximum likelihood estimator is biased. Alternative estimators, including an unbiased estimator and an optimal estimator, are discussed.The results are also briefly discussed in the context of an actual model experiment with ultrasound in air. A side effect of this is the demonstration of certain issues which have been ignored in the previous general discussion. The experiment also indicates that the results are relevant in other contexts. Other important classes of examples are given by Real Time Locating Systems as defined by the standard ISO/IEC 24730, and by Wireless Personal Area Networks as described in the IEEE 802.15 standard. These other contexts also provide most useful sources for research publications with results of relevance for UPS, and more generally for underwater communication systems.

Survey of computer vision algorithms and applications for unmanned aerial vehicles

“…Global Positioning System (GPS) ( Kaplan & Hegarty, 2006;Zogg, 2009 ) or the Satellite-based Navigation System (SNS) is considered as one of the most known approaches that is used with UGVs ( Abbott & Powell, 1999;Amini, Vaghefi, de la Garza, & Buehrer, 2014;Wei, Cappelle, & Ruichek, 2011;YA GIMLI & Varol, 2009;Yoon, Park, & Kim, 2006 ), UAVs ( Cho et al, 2007;Hui et al, 1998;Isaacs et al, 2014;Kim, 2004;Yun, Peng, & Chen, 2007 ) or even Autonomous Underwater Vehicle (AUV) ( Lee, Li, Hoang, & Lee, 2014a;Meldrum & Haddrell, 1994;Taraldsen, Reinen, & Berg, 2011 ) to provide the 3D position for navigation purposes.…”

Calibration and Validation of the Intel T265 for Visual Localisation and Tracking Underwater

“…One of the difficult aspects of this endeavour is that approaches that work on land not necessarily translate that well into underwater environments. For example Global Positioning System (GPS) will only work above water (Taraldsen et al, 2011), because of the disturbances under water, laser based approaches tend to have difficulties as a result of the light refraction.…”

Comparison of Dynamic and Kinematic Model Driven Extended Kalman Filters (EKF) for the Localization of Autonomous Underwater Vehicles

“…Tables 5 and 6 provide the RexROV parameters and coefficients that are used in the equations ( 27) to (30). These coefficients are specific to RexROV as shown in 2 and are derived from Berg's model [17] and UUVSim [14].…”