Mapping data mainstream status quo at home and abroad
Since the dawn of history mankind, we continue to explore and recognize their own in which the natural system, and try various ways to describe the expression of the space environment information. With the development of information technology, geographic information technology deeper in engineering applications, the role of mapping geographic information will become increasingly important. New information dissemination, new application requirements, necessitating new demands for production, management and expression of terrain information.
Digital Elevation Model
Digital elevation model (Digital Elevation Model, DEM) data organization and forms of expression that contains point, line, surface-like forms in the application of digital terrain and theoretical research project, the main structural model DEM regular grid model , TIN model ( Digital the Elevation the model , the TIN) and contour models, other models such as the cross-section, scatter model, hybrid model (SURVEYING, 2001) applied less. Where research and engineering applications regular rectangular grids and TIN more common.
Regular grid model and triangulated irregular network model has its own characteristics, but the most practical method of terrain analysis is based on grid DEM's (Qing Zhu et al., 2004; Jiang Fan et al, 2007), the reason , DEM simple grid structure, with characteristic matrix structure on a flat surface topology, so that the matrix based mathematical methods can be used to analyze the application of the terrain, with its emphasis on simple matrix structure characteristics. Without regular triangulation variable resolution grid structure to avoid problems arising uniformity, the structure will be more "close" surface morphology.
Digital orthophoto
The process of digital orthophoto (Digital Orthophoto Map, DOM) showed a very important role in the development of remote sensing technology, on its research also rapidly in recent years in development, Hao Si Bao (2007) studied the digital orthophoto built library , through the construction of a digital image database, you can be more rapid indexing and sorting various data required for digital video, in addition to the use of space-time relational data model and its features, an effective solution to image data updated in real time and historical data; Liu Shuhui (2013) use Inpho process producing digital orthophoto FIG noted that the processing flow in the problems, and find the corresponding algorithm can reduce the error, then related industries produce precise digital orthophoto provides a wealth of experience and methods; for digital orthophoto imaging products to promote the practical application of various types of terrain in our country, the corresponding ortho-rectification model for digital images of more comprehensive studies.
With the development of digital photogrammetry, photogrammetric technology into the semi-automated and intelligent stage is now in the efficient, low-cost, high-precision progressive objectives. Beginning in the 1990s, a variety of functions fairly complete digital photographic image measuring system (Digital Photogrammetry System, DPS) and digital photogrammetric workstation (Digital Photogrammetry Workstation, DPW) have been put into the market. At present, foreign more famous digital photographic image measuring system the United States Intergraph's Image Station system, Leica's Helava system and ERDAS LPS, Germany Zeiss PHODDIS system, Germany's Inpho system, France Inforterra company Pixel Factory (PixelFactory) and US BSR System's Socet Set and so on.
DLG
In this era of computer networks flooded, if only just to provide information on a paper map or some old digital map has been unable to meet research needs. In order to comply with the development, the application of digital mapping is more and more widely in our daily life.
Digital line in FIG. (Digital Line Graphic, DLG), which refers to a topographic map in the existing the geographic features stratified storage, send, measure its vector data, and then based on these data object attributes the query vector, a point, line, surface, or in the form of graphic symbols in the form of a specific map, the expression vector GIS data set of terrain features. Feature point is represented as a set of coordinates and the corresponding attribute values in the vector data; feature represented as a series of lines and the corresponding coordinate set of attribute values; end-face feature point is expressed as a string of coordinates coincident attribute values and the corresponding group. DLG is an important part of the world the results of basic geographic information digital countries.