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Future wide-area surveillance systems mounted on unmanned air vehicles (UAVs), such as Tier II+, will be capable of collecting SAR imagery at prodigious coverage rates (greater than 1.5 km2/sec, 1 m resolution). One important consideration for making such systems economically feasible is squeezing the large amount of SAR imagery through an available communications link. When the sensor platform is beyond the line of sight from the ground processing facility, it is highly desirable to transmit the imagery via a 1.5 megabit per second T1 satellite communications data link; it would be prohibitively expensive to ensure the availability of a wider bandwidth satcom link at any point on the globe. Use of a T1 link creates an onerous burden for SAR image compression algorithms. In the Tier II+) scenario, for example, use of a T1 link implies a compression rate of less than half a bit per pixel. In the longer term, systems will have greater coverage areas and higher resolution capabilities; the compression requirement will be substantially more severe. Conventional image compression algorithms are incapable of attaining the required compression while retaining the image fidelity required for processing at the ground station. Clipping service is a system concept that reduces communication requirements by using automatic target detection and recognition (ATD/R) algorithms onboard the UAV. The ATD/R algorithms identify regions of interest in the collected imagery. In the regions of interest, the imagery is transmitted with highest fidelity. In other areas, the imagery is transmitted with less fidelity, thereby reducing the communication bandwidth required. In this paper, we describe a multiple-resolution clipping service system. In this system, regions of interest are identified by ATD/R algorithms. The regions of interest are transmitted at the finest resolution achievable by the sensor; elsewhere, imagery is transmitted with reduced resolution and reduced data rate. The system utilizes a multiple-resolution image formation algorithm to reduce computational load: ATD/R algorithms are applied to coarse resolution imagery; the imagery is subsequently processed to fine resolution imagery only where targets are likely to be present. This reduces computation because only a fraction of the imagery is processed to fine resolution. In the paper, we determine the communication requirements for the multiscale system assuming Tier II+ parameters. We demonstrate that it is feasible to transmit Tier II+ imagery via a T1 data link using the clipping service concept.
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