X. Liu, Q. Du, T. Liu

School  of  Resource  and  Environment Science,Wuhan University, 129 Luoyu Road,Wuhan 430079, China


Augmented Reality(AR) is a technology that overlays virtual image and information generated by computer on real world seen by the user ,it can provide a more nature user interface for engineers and establish fascinating environment for education and entertainment applications. Outdoor Augmented Reality is a new direction in the field of AR research in recent years,its difficulty is concentrated on the sensor technology and registration .ARToolKit provides a convenient and quick tool to develop AR application ,but its registration method is based on computer-vision .Outdoor environment is complicated,so ARToolKit must be improved to suit for outdoor AR application.

     In this paper, author put forward a hybra registration based on GPS and electronic compass in an outdoor AR system.Central system receives original observational data from GPS and electronic compass,and send them to the DBMS passing through revising. Then the data and virtual object could be put into the database .When user is padding in the environment,system can select appropriate virtual object to match real scence on the foundation of data from the sensors.

This paper includes some sections ,as following: Firstly,introducing the system structure 、 work flow and developing flow of ARToolKit ; Secondly,performeing indoor Augmented Reality with ARToolKit to validate the registration algorithm based on markers;Thirdly, the key technologies of system ,for example 3D registration technology 、display、tracking 、virtual modeling technology and spatial database, are introduced in detail; Fourthly, according as the real instance puting forward a hybra registration based on GPS and electronic compass in an outdoor AR system .In this section ,we bring forward the frame including the hardware and software needed ,the function including enhancing the virtual information、querying the attribute value、navigation and spatial measure .Application of outdoor AR system are  also completed,because ARToolKit is based on computer-vision, we must amend some functions to accommodate the outdoor AR system found on sensor and add some functions to take over the data from sensors. Virtual objects are created by VRML or 3D max ,all of the procedures are integrated in Visual Studio 2005.Finally,in view of huge error of data provided by GPS and the electronic compass,we must adopt some methods of improving the registration precision to achieve good precision.