Integration of Global Positioning System and Inertial Navigation for Ubiquitous Context-Aware Engineering Applications

Context aware computing offers significant potential of improving decision making tasks in several engineering applications by providing support for tedious and time consuming activities associated with timely and accurate access to needed information. Bidirectional flow of information relevant to the spatial context of a mobile user requires continuous and accurate tracking of the user’s position and orientation. The tracking technology used cannot be dependent on installed infrastructure because it is not possible to install such infrastructure in every building. Additionally, a disaster may cause partial or complete damage to the installed infrastructure itself. To overcome this problem, this paper presents research that investigated the development and effectiveness of a ubiquitous location tracking system based on the integration of Real Time Kinematic Global Positioning System (RTK-GPS) and Personal Dead Reckoning (PDR) technologies for dynamic user position tracking. 1. Importance of the research: Context aware computing is defined as the use of environmental characteristics such as a user’s location, time, identity, profile and activity that is relevant to the current context [3]. Context aware computing can thus potentially enable mobile users (e.g. construction inspectors, fire fighters) to leverage knowledge about various context parameters to ensure that they get highly specific information, pertinent to the decisions at hand. The relevance for context awareness for mobile users has been demonstrated in several applications [1]. The concept of context-aware information delivery [1] centers around the creation of a user centered mobile dynamic indoor and outdoor work environment, which has the ability to deliver relevant information to on-site mobile users by intelligent interpretation of their characteristics in space and time so that they can take more informed decisions [8]. Context awareness is of great value for civil engineering inspectors, emergency responders, security and military personnel. For example, tracking civil engineers during post disaster assessments, or while conducting bridge inspection reports, can allow bi-directional flow of streamlined information and thereby improve the efficiency of the decision making processes. RTK-GPS is a convenient option to track a mobile user continuously in an outdoor environment. It is highly accurate and is free of accumulated errors. GPS, being a satellite-based navigation system, works very well outdoors but lacks support indoors and is unreliable in dense foliage, in so called “urban canyons” and generally in any environment where a clear line of sight to the satellites is unavailable. In recent years, the need for indoor localization has been rapidly expanding in many fields and currently offers significant potential on construction sites in particular. However, unlike outdoor areas, the indoor environment imposes different challenges on location discovery due to the dense multipath effect and building material dependent propagation effect [5]. There are many potential technologies and techniques that have been suggested to offer the same functionality as a GPS indoors, such as Wireless Local Area Networks (WLAN), Ultra-Wide Band (UWB) and Indoor GPS. By tagging users with appropriate receivers/tags and deploying a number of nodes (access points, receivers, transmitters, etc.) at fixed positions indoors, the location of tagged users can conceptually be determined and continuously tracked by fingerprinting and triangulation. A detailed comparison of the WLAN, UWB and Indoor GPS systems has also been done in a recent study [6]. The main drawback of the aforementioned indoor tracking technologies is their dependency on pre-installed infrastructure making them unsustainable in a dynamic environment. To overcome this shortcoming, the authors have developed a Personal Dead Reckoning (PDR) system that does not require pre-installed infrastructure. The Inertial Measurement Unit based PDR system is very accurate in measuring linear displacements (i.e., distance travelled, a measure similar to that provided by the odometer of a car) with errors being consistently less than 2% of the distance travelled. The accuracy of the PDR system, however, NSF GRANT # 0927475 NSF PROGRAM NAME: CMMI/CIS