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An Innovative System for Low Cost Airborne Video Imaging
 Paul Maxwell DARE Spatial Scientific Technologies Pty. Ltd. PO Box 520, Blackwood, SA 5051, AUSTRALIA Ph: +61 405 141 647; Fax +618 8278 8067 Email: paul@spatialscientific.com.au Abstract: Airborne video imaging has been used for many years for various mapping applications worldwide. Experience has shown that it is a technology that is neither well-suited to spectral remote sensing (due to its poor spectral capabilities), nor is it well-suited to spatial remote sensing (due to its poor geometric properties). Even so, airborne video imaging has proved enormously popular for some very specific mapping applications. One such application is mapping of linear infrastructure features, such as roads, pipelines or powerlines. Any country, whether developing or developed, can benefit from mapping of its linear infrastructure assets. However, to derive full benefit from this type of mapping, the data collection and processing must be both cost-effective and efficient. This paper presents an innovative yet low cost methodology for acquiring airborne video data, based on the use of an aircraft known as a powered parachute (PPC). A PPC is a low cost, simple aircraft which can fly safely at low speeds and altitudes, but still provides an extremely stable platform for imaging sensors. Tests carried out in Australia have shown it to be an ideal platform for airborne video imaging of linear features. However, the choice of platform is only part of the system – the remaining component, which is no less important, is the software that is used to process the video data. Over the years many different algorithms have been developed for mosaicking video images into continuous scenes. This paper also presents a methodology for rectifying, processing, and analysing sequential video images. The resulting combination of platform, camera and software forms an ideal system for asset mapping, which can realistically be implemented in less developed countries. 1. Introduction Over the years, the term ‘airborne video’ has been used for many different types of airborne imaging technology. Historically, airborne video has referred to any airborne image data that did not come from film-based cameras, either small or large format, or digital line scanners. Thus early airborne video systems were based around analogue video cameras. However, as technology progressed, the term airborne video was also used to describe early small format digital frame cameras. Now that small format digital cameras (and large format ones as well to some extent) are ubiquitous, the term digital aerial photography is better used to describe image acquisition form these types of cameras. Consequently, the term airborne video now best describes imaging from a video camera, either analogue or digital. This paper is therefore concerned with only those sensors, and not the wider spectrum of digital airborne cameras. Airborne video imaging has been used for remote sensing applications for many years. Early airborne video systems relied on analogue data, whereas more recent systems make use of digital video or even high definition video. Previous catalogued uses of airborne video are numerous, but include environmental mapping, natural resource management and asset mapping. Examples of environmental mapping where airborne video systems have been used include agricultural assessment [1], forest health mapping ([2], [3]) and coastal zone monitoring [4]. Linear asset mapping applications have also been described ([5], [6]). The advantages of using airborne video for remote sensing applications are cost and simplicity. The disadvantages are that the data lacks the geometric quality of digital SLR cameras, as well as lacking the spectral quality of digital multispectral cameras. In the past, use of video was justified since it was probably the only true low cost sensor available. However, nowadays the wide availability of many advanced digital still cameras which are priced at the same level as digital video cameras means that the use of airborne video is much more difficult to justify. Consequently, airborne video should now only be used for niche applications where other sensors are just not suitable. The keys to the successful use of any remote sensing system is choosing the correct sensor for the application, and using the appropriate platform. This is also true for airborne video. Modern airborne video is ideally suited to low budget applications where rapid data delivery is required, but where spectral and spatial quality is not paramount. Alternatively, airborne video can be a valuable source of spatial data when it is literally impossible to acquire any other data. In order to support these applications, the video sensor must be mounted on a flexible, low cost platform. This paper proposes the use of a powered parachute as a platform for the airborne video imaging system. This novel concept will likely to prove itself extremely valuable in certain niche applications, both in developing and developed nations. The three components to the innovative imaging system described in this paper are:
2. Video Imaging Devices
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