With the development of remote sensing and aero photography, we can quickly get all kinds of inexpensive image with
high resolution. To efficiently manage these increasing high-volume data, the spatial database management system is the
best solution. In this paper many problems and key techniques are analyzed and discussed on establishing remotely
sensed image database, including image dividing, image encoding, image indexing, establishment of image pyramid, etc.
To the question of buffer generation for linear objects in GIS, nowadays most of existing studies devote to the algorithms of buffer generation in which the factor of director is not considered because of its complexity, and few people pay attention to study on the lateral buffer generation. This paper attempts to explore and give some preliminary solutions about the lateral buffer generation for linear objects. First it discusses the definition of left and right sides about linear objects, and a new method to determine the lateral relation is designed based on this definition. Furthermore, it puts forward two methods of lateral buffer generation, and gives the implementation steps in detail. In addition, the paper takes some vivid examples to analyze the characteristic and potential problems of these two methods, which have some referenced value to the kindred researches in algorithm design of lateral buffer generation.
The pollution of urban electromagnetic radiation has become more serious, however, there is still lack of a perfect and
interactive User System to manage, analyze and issue the information. In this study, taking the electromagnetic
environment of Nanjing as an example, an information system based on WebGIS with the techniques of ArcIMS and JSP
has been developed, in order to provide the services and technique supports for information query of public and decision
making of relevant departments.
Delaunay triangulation is always used to construct TIN, and is also widely applied in manifold fields, for it can avoid
long and skinny triangles resulting in a nice looking map. A wide variety of algorithms have been proposed to construct
delaunay triangulation, such as divide-and-conquer, incremental insertion, trangulation growth, and so on. The
compound algorithm is also researched to construct delaunay triangulation, and prevalently it is mainly based on divide-and-conquer and incremental insertion algorithms. This paper simply reviews and assesses sweepline and divide-and-conquer
algorithms, based on which a new compound algorithm is provided after studying the sweepline algorithm
seriously. To start with, this new compound algorithm divides a set of points into several grid tiles with different
dividing methods by divide-and-conquer algorithm, and then constructs subnet in each grid tile by sweepline algorithm.
Finally these subnets are recursively merged into a whole delaunay triangulation with a simplified efficient LOP
algorithm. Because topological structure is important to temporal and spatial efficiency of this algorithm, we only store
data about vertex and triangle, thus edge is impliedly expressed by two adjacent triangles. In order to fit two subnets
merging better, we optimize some data structure of sweepline algorithm. For instance, frontline and baseline of
triangulation are integrated into one line, and four pointers point to where maximum and minimum of x axis and y axis
are in this outline. The test shows that this new compound algorithm has better efficiency, stability and robustness than
divide-and-conquer and sweepline algorithms. Especially if we find the right dividing method reply to different
circumstance,its superiority is remarkable.
With the recent availability of commercial high resolution remote sensing multispectral imagery from sensors such as
IKONOS and QuickBird, we can't get the accuracy of land-cover classification expected using pixel-based approach. In
this paper, we bring about object-based approach combined with the nearest neighbor to classify the QuickBird image of
LianYungang city. Firstly, the image is segmented into object feature, we make the shape feature and contextual relation
feature join the new feature space which is used to classify. And then we compare the classification of object-based
approach accuracy with the nearest neighbor method of classification result, we can draw a conclusion that the method of
classification in this paper can recognize geo-types much better. And the overall accuracy is 92.19%; the coefficient of
Kappa is 0.8835. Salt and pepper effect is decreased effectively. The result indicates that the approach of land-cover
classification combined object features with the nearest neighbor approach supplies another new technique for interpreting
high resolution remote sensed imagery.