Uniform Indexing for Geospatial Data and Authorizations

Abstract

High-resolution satellites are promising technologies to bolster global transparency by providing unprecedented access to accurate and timely information. A significant number in this satellite fleet are owned by private organizations, which can collect images of human activities and the environment, and make them commercially available around the globe. Uncontrolled dissemination of this information may have grave implications on national security and personal privacy, as some governments and private groups may exploit this information for aggressive purposes. Formal policies for prohibiting the release of imagery beyond a certain resolution, and notifying when an image crosses an international boundary or when such a request is made, are beginning to emerge. As such, there is a need for effective and efficient schemes for facilitating controlled dissemination of satellite imagery and the information products generated from it. Unlike conventional authorizations that can be implemented as access control lists, since authorizations on geospatial imagery involve spatial attributes, managing the authorization base and searching for authorizations based on the spatial extent require a spatial indexing structure. An access request thus requires a search on two index structures, one for the authorizations, and the other for the image database. In this paper, we propose an indexing structure, called RMX-quadtree, that is capable of indexing multi-resolution satellite imagery and additionally allow representing authorizations on top of it. By employing a uniform index for both image database and authorization base, access requests can be processed more efficiently as only one index structure need to be traversed. We demonstrate how authorizations with privilege modes such as view and zoom-in can be implemented using the RMX-quadtree.