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The accelerating rate of change in urban areas calls for more rapid and cost-effective surveys of derelict land. A review of the use of remote sensing' for this task reveals that, although aerial photography has been used for urban analysis since the 1940s, it has not been widely adopted for surveys of derelict land, despite demonstrations of its utility. Other forms of remote sensing are similarly shown to have been little-used and to have had patchy success. The hitherto restricted utility of remote sensing is found to be due to a combination of limitations of the forms of imagery available and the methods of analysis employed. Recent changes in available remote sensing imagery, notably the higher resolution now provided by the SPOT satellite, coupled with advances in digital image-processing techniques point to improved opportunities for using remote sensing to monitor derelict land. As a demonstration of these developments, a texture image based on scene variance is derived from a SPOT image of part of north Staffordshire. All derelict and neglected land parcels larger than 1.25 ha are delimited on this image. Remote sensing techniques are not yet ready to supplant detailed ground surveys but they have a growing role to play in monitoring various aspects of land dereliction. KEY WORDS Derelict land Remote sensing Image texture Land uselland cover monitoring

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Panel ThemeRecently, there has been a tremendous growth in real-time collaboration products and services. Real-time collaborative technology enables synchronous communication for a variety of purposes, including whiteboards, chat, Internet phone, video and audio conferencing, desktop-to-desktop videoconferencing, group management, forecasting, polling, voting and application sharing. Most synchronous collaboration product suites are highly complex and their protocols are relatively new, which typically raises a "red flag" for those who have been around the security block a few times.This panel consists of security experts from the government and private sectors who represent the consumer, research and vendor communities. Panelists will provide three different perspectives on collaborating securely. Bill Dawson will provide a government perspective on Enabling Collaboration with PKI. Jeff Ingle will discuss Research Issues for Secure Collaboration. Steve Lipner will round out the discussion with a ,vendor's perspective.