The paper presents a smartphone-based shooter localization system. As muzzle blasts are difficult to detect at longer distances and consequently present higher false detection rates, the system relies on shockwaves only. Each sensor uses four microphones to detect the Angle of Arrival and the length of the shockwave. This information, along with the sensor's own GPS coordinates, are shared among nearby smartphones. Assuming a known weapon type, it then proceeds to estimate the two possible projectile trajectory candidates for each sensor that are consistent with the observations in the horizontal plane of the sensors. A simple clustering algorithm identifies the correct projectile trajectory relying on as few as two sensors. The trajectory is then used to estimate the bearing to the shooter relative to each sensor. The paper presents the overall system architecture, the design of the sensor node that interfaces with the smartphone, the trajectory and bearing estimation algorithms, and the evaluation of the system based on a field experiment.

The World Wide Web provides unprecedented access to globally distributed content. The extent and uniform accessibility of the Web has proven beneficial for research, education, commerce, entertainment, and numerous other uses. Ironically, the fact that the Web is an information space without boundaries has also proven its biggest flaw. Key aspects of libraries, such as selectivity of content, customization of tools and services relative to collection and patron characteristics, and management of content and services are noticeably absent. Over the past four years, we researched the technology and deployment of a digital library architecture that makes it possible to create managed information spaces, digital libraries, within the World Wide Web. Our work has taken place in the context of NCSTRL,1a digital library of computer science research reports. The technical foundation of NCSTRL is Dienst, a protocol and architecture for distributed digital libraries that we developed as part of the DARPA-funded Computer Science Technical Reports Project. At the time of the writing of this paper, the NCSTRL collection consisted of papers from more than 100 research institutions residing in servers distributed across the United States, Europe, and Asia. In addition, the Dienst protocol and implementation has been successfully adopted by a number of other distributed collections. In this paper, we review our experiences with NCSTRL and Dienst, describe some of the lessons we have learned from the deployment experience, and define some directions for the future.

The goal of drop-in publishing is to simplify digital publishing over the Internet. We would like digital publishing of non-commercial matter (e.g. technical reports, course notes, brochures) be as easy as sending e-mail is now, but with the virtues of archival storage and easy searching that we associate with electronic libraries. We propose a protocol, Dienst, to allow communication between clients and document servers by encoding object-oriented messages within URL's. A preliminary version of this protocol now runs at eight sites, and we deseribe some of its features. Next we present tools for automating the maintenance of document collections. Finally, we discuss the problems we've had with the Web as it stands, hoping to motivate changes that would improve performance of digital library systems such as ours.