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Spatial data structures have evolved under the influence of several forces: 1) Database technology, with its emphasis on modeling and logical organization; 2) the long history of data structures developed in response to requirements from other applications; and 3) the recent rapid progress in computational geometry, which has identified typical queries and access patterns to spatial data. Rather than...
Efficient access methods, such as indices, are indispensable for the quick answer to database queries. In spatial databases the selection of an appropriate access method is particularly critical since different types of queries pose distinct requirements and no known data structure outperforms all others for all types of queries. Thus, spatial access methods must be designed for excelling in a particular...
A quadtree-like representation for storing gridded elevation data is described. The data structure is a pyramid with each node containing two bits of data. The root of the pyramid has associated with it the minimum elevation for the corresponding grid and the maximum variance (the difference between the minimum and maximum values). The elevation value at any pixel is calculated by traversing a path...
The DASDBS GEO-Kernel, a member of the DASDBS family, has been developed as an extension of the DASDBS kernel system, especially configurated for the management and manipulation of geoscientific data. It is a combined approach using a new powerful data model for the description of storage structures and a set-oriented user interface with an Object Buffer and extensibility to achieve a closer connection...
In the past few years a large number of multidimensional point access methods, also called multiattribute index structures, has been suggested, all of them claiming good performance. Since no performance comparison of these structures under arbitrary (strongly correlated nonuniform, short "ugly") data distributions and under various types of queries has been performed, database researchers...
Several spatial access methods can handle non-point data by placing each data object in a container, e.g. a box, and storing the collection of containers. As complexity of the spatial objects increases, the effectiveness of this strategy decreases, due to the inaccuracy of the approximation. Some access methods store objects redundantly to compensate. Each copy represents some portion of the object...
Geographical variation is infinitely complex, so the information coded in a spatial database can only approximate reality. The information will always be inadequate, in spatial resolution, thematic or geographical coverage. "Large" can be usefully defined as exceeding our current capacity to deliver. We provide examples of large geographical databases. Traditional stores partition geographical...
This paper presents an approach to handle environmental measurement data within a relational database. The approach has been developed within a cooperative environmental research project exploring the contamination of groundwater and soil. Considering the special properties of measurement data we suggest an extension to data retrieval that allows the user to query measurement attributes without knowing...
We study here how to provide the designer of geographic databases with a database query language extensible and customizable. The model presented here is a first step toward a high level spatial query language adapted to the manipulation of thematic maps. For this, we take as an example a toy application on thematic maps, and show by using a complex objects algebra that application dependent...
An overview is presented of the use of hierarchical spatial data structures such as the quadtree. They are based on the principle of recursive decomposition. The focus is on the representation of data used in image databases. The emphasis is on two-dimensional regions, points, rectangles, and lines.
Quadtrees have been widely used in computer vision, spatial database, and related area due to their compactness and regularity. It has long been claimed that quadtree related algorithms are suitable for parallel and distributed implementation, but only little work has been done to justify this claim. The simple input partitioning method used in low level image processing could not be equally applied...
A method, termed approximate splitting, is proposed to model the node distribution that results when the PR quadtree is used to store point data drawn from a uniform distribution. This method can account for the aging and phasing phenomena which are common in most hierarchical data structures. Approximate splitting is also shown to be capable of being adapted to model the node distribution of the...
The applicability of the Object-Oriented (OO) approach to Geographic Information Systems (GISs) is analyzed. In software engineering, the OO approach as a design model, has been proven to produce quality software. It appears that GISs might also benefit from the OO approach. However, a GIS also imposes special (e.g. spatial) requirements, inclusion of which in the OO model has to be investigated....
There is a growing demand for engineering applications which need a sophisticated treatment of geometric properties. Implementations of Euclidian geometry, commonly used in current commercial Geographic Information Systems and CAD/CAM, are impeded by the finiteness of computers and their numbering systems. To overcome these deficiencies a spatial data model is proposed which is based upon the mathematical...
A dynamic file structure for spatial object storage and access is described. Based on an extension of the BANG file, it has a self-balancing, tree-structured directory with the following properties: no replication of object instances worst-case search, insertion (excluding overflow) and deletion (excluding underflow) of an individual object requiring no more page accesses...
We present a methodology for pictorial database design, based upon a new spatial knowledge structure. This spatial knowledge structure consists of an image database, symbolic projections representing the spatial relations among objects or sub-objects in an image, and rules to derive complex spatial relations from the generalized 2D string representation of the symbolic projections. The most innovative...
Spatial knowledge is rarely introduced in knowledge based systems while those systems are able to reason in space. This paper presents a definition of spatial reasoning with a classification of spatial knowledge and describes several properties and needs of spatial reasoning. Two examples of applications concerning symbolic simulation and geographic information data management are surveyed. Object...
Qualitative reasoning is useful as it facilitates reasoning with incomplete and weak information and aids the subsequent application of more detailed quantitative theories. Adoption of qualitative techniques for spatial reasoning can be very useful in situations where it is difficult to obtain precise informationand where there are real constraints of memory, time and hostile threats. This paper formulates...
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