CLASSIFICATION OF REMOTE GEOGRAPHIC IMAGES

The article considers the properties of remote geoimages. The properties of remote geoimages are singled out; the system ofclassification features is developed. The classification features of remote geoimages are divided into two groups: features of thewhole work and features of the iconic image. The first are the features that apply to the whole work, is visualized digital oranalogy display on any media. These include: recording information, repeatability, print format and image construction andproduction technology and registration and destination materials. The second group of features includes the features of thedirectly iconic image, what we can see in the picture. These are coverage of the territory, signs of image characteristics (spatial,spectral, radiometric and temporal resolution), detail, spectral range and degree of reduction. The following properties of remotegeoimages are distinguished: visibility, complex mapping of geosphere components, regular repeatability of shooting, remotegeneralization of the image, objectivity, efficiency, extraterritoriality, accessibility. The correspondence of the properties ofremote geoimages to their classification features is outlined. On the basis of the developed classification features theclassification of remote geoimages is created. The developed classification of remote geoimages according to certain features isthe most complete and systematized ordering of currently known types of remote geoimages. The developed classification willbe included in the analytical and information system for geo-iconic visualization and construction of geoimages with givenproperties. The classification is designed with the possibility of updating and supplementing, which provides for its furtherimprovement.

ON THE EXPECTED SIZE OF THE 2D VISIBILITY COMPLEX

We study the expected size of the 2D visibility complex of randomly distributed objects in the plane. We prove that the asymptotic expected number of free bitangents (which correspond to 0-faces of the visibility complex) among unit discs (or polygons of bounded aspect ratio and similar size) is linear and exhibit bounds in terms of the density of the objects. We also make an experimental assessment of the size of the visibility complex for disjoint random unit discs. We provide experimental estimates of the onset of the linear behavior and of the asymptotic slope and y-intercept of the number of free bitangents in terms of the density of discs. Finally, we analyze the quality of our estimates in terms of the density of discs.

THE VISIBILITY COMPLEX

We introduce the visibility complex (a 2-dimensional regular cell complex) of a collection of n pairwise disjoint convex obstacles in the plane. It can be considered as a subdivision of the set of free rays (i.e., rays whose origins lie in free space, the complement of the obstacles). Its cells correspond to collections of rays with the same backward and forward views. The combinatorial complexity of the visibility complex is proportional to the number k of free bitangents of the collection of obstacles. We give an O(n log n+k) time and O(k) working space algorithm for its construction. Furthermore we show how the visibility complex can be used to compute the visibility polygon from a point in O(m log n) time, where m is the size of the visibility polygon. Our method is based on the notions of pseudotriangle and pseudo-triangulation, introduced in this paper.