u indoor tracking system that covers a substantial part

u  In
this work we investigate building indoor location based applications for a
mobile augmented reality system. We believe that augmented reality is a natural
interface to visualize spatial information such as position or direction of
locations and objects for location based applications that process and present
information based on the user’s position in the real world.

u  To
enable such applications they construct an indoor tracking system that covers a
substantial part of a building. It is based on visual tracking of ?ducial

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u  Augmented
reality (AR) is a powerful user interface technology that augments the user’s
environment with computer generated entities.

u  The
?rst application is a navigation guide called Signpost that supports the user in
?nding a desired location within our building. It provides her with directional
hints and highlights exits of rooms to be taken to proceed towards the
destination. The second application is a a search and retrieval application
that helps a library visitor to locate a desired book or its designated place
in the library bookshelves.

u  Outdoors,
GPS provides global position with accuracy between several meters and

u  Indoors,
tethered tracking systems using magnetic and ultrasonic techniques to achieve
high accuracy in the millimeter to centimeter range.

u  Computer
vision also be used to track the movement of a camera.

u  OpenTracker
an open software architecture for the di?erent tasks involved in tracking input

u  Interaction
with the application is attained through a user interface displayed on the
wrist pad.

u  The
system continuously provides the user with two mode s of visual feedback. A
heads-up display with directional arrows and a world in miniature model of the

u  Using
this adjacency graph, the application is able to compute the shortest path
between two rooms. This is done by utilizing an algorithm based on the shortest
path algorithm introduced by Dijkstra.

u  In
this mode, ARLib attempts to detect markers that are attached to books. If a
marked book is spotted, all available information about the publication is
presented on the wrist panel, and the book’s designated position on the shelf
is highlighted to aid the user in returning the book to its correct position.

u  The
tracking error varies largely. As long as markers were continuously visible the
augmentation of the room geometry is fairly stable and correct. However as soon
as all markers are obscured the tracking can only rely on the inertial tracker
and starts to become incorrect

u  This
led to the conclusion that more markers are needed to improve the quality of
the tracking. The directional arrows also performed better than the
highlighting of the portals under such circumstances as the information they
provide is less prone to tracking errors.