Quản lý của DTM dữ liệu Trong chương 9, nó đã được thảo luận rằng các dữ liệu DTM đã trở thành một phần của một NSDI và một thường được sản xuất ở cấp độ quốc gia với nhiều quy mô. Đối với các nước lớn như Brazil, Canada, Trung Quốc, Ấn Độ, và Hoa Kỳ, khối lượng dữ liệu DTM có thể là rất lớn. Vì vậy, hiệu quả quản lý của DTM dữ liệu trong một hệ thống máy tính là một nhiệm vụ quan trọng tại các trung tâm thông tin không gian địa lý quốc gia. | CHAPTER 10 Management of DTM Data In Chapter 9 it was discussed that DTM data have become part of an NSDI and one usually produced at the national level with multi-scales. For large countries like Brazil Canada China India and the United States the volume of DTM data could be huge. Therefore efficient management of DTM data in a computerized system is an important task at national or provincial geospatial information centers. Therefore this chapter is devoted to management of DTM data. STRATEGIES FOR MANAGEMENT OF DTM DATA Spatial data including DTM data must be managed efficiently and database technology plays an important role. There are different strategies to deal with the problems in the management of DTM data. Strategy for Making DTM Data Management Operational To make the management of spatial data operational spatial data sets are partitioned according to five attributes horizontal or vertical positions time theme and scale. In the management of DTM data scale and horizontal positions are used. The use of scale was discussed in Chapter 9 and therefore only the use of horizontal position will be described in this section. If the area to be modeled is large such as a nation or a province one is concerned with the arrangement of the huge volume of DTM data. Questions such as should distributed or centralized databases be used or how can the data of the whole area be split into small pieces so that they can be managed efficiently are the concern here. As contour maps have been widely used for DTM production DTMs at a national scale are usually arranged in a way similar to map sheets. Figure shows the arrangement for the 1 1 000 000-scale topographic maps of China. Table shows the size of each map sheet at different scales ranging from 1 1 000 000 to 211 2005 by CRC Press 212 DIGITAL TERRAIN MODELING PRINCIPLES AND METHODOLOGY Figure The tiling system of China s map sheets at 1 1 000 000 scale. Courtesy of the National Geomatics Center
