11.4.3.1 Basic geographic data processing and organization
Basic geographic data comprehensively reflect the natural geographic conditions and socio-economic conditions within the database coverage, and can be used as the basis for spatial positioning of each topic in the comprehensive survey of remote sensing of land resources. The basic geographic data of this remote sensing comprehensive survey is provided by Zhejiang Provincial Bureau of Surveying and Mapping, with a scale of 1:250,000, adopting latitude and longitude coordinate system, and the file record format of MapInfo's TAB format. It describes the topographic elements such as water system, contour lines, boundaries, transportation, and settlements with vector data structure, and also includes the spatial relationship between topographic map elements and related attribute information. The whole set of data*** is divided into Areaboul (Boundary), Villres (Village Residence), Townres (Township Residence), Text (Village and Township Residence Notes), Hydroano (Water System, Peak, Island Notes), Counres (County Residence), Counano (County Residence Notes), Areares (Municipal Residence), Areaano (notation of municipal offices), Bridglk (bridges), Mairoalk (highways, national and provincial highways), Secroalk (county and township highways), Railk (railroads), Terlkla (contour lines), Respy (settlements), Hydlk (lineal water systems), Hydnt (surface water systems), Merbount (1:250,000 maps), and other maps. 1:250,000 map contour), Counbou (county administrative area), Areabou (municipal administrative area), and other ***20 layers of thematic elements.
Before the data enter the GeoDatabase, the first information preprocessing is carried out, checking whether the perimeter of the administrative areas at all levels on the 1:250,000 basic topographic map is strictly closed, and the non-closed perimeter has to be closed; checking the consistency of the road section and the river section on the map, and connecting the homonymous line segments into a whole and labeling them with the names; and checking the leakage, multiple points, leakage, multiple lines, and the point and line offset; Check the contour lines of the error and omission; check the map on the lines, symbols, notes between the avoidance and cover, not in line with the requirements of the library to make a number of adjustments.
After inspection and correction of the data, it is also necessary to standardize the processing. The so-called standardization, that is, the data will be organized to meet the standards that have been developed in the process, here mainly refers to some of the pre-processing before entering the GeoDatabase, mainly for various types of data items to check, the requirements of the data after the initial processing to achieve the unity of the type of uniformity, the length of the number of unity, the unity of the unit of measurement and precision, etc.; and to deal with the situation of the missing data.
Finally, the corresponding data will be processed by logical hierarchical categorization, and each major category will be divided into layers according to the mechanism of physical storage (GeoDatabase) and the type of entities (points, lines, surfaces, and notes), and the different vector element classes will be organized into a vector element dataset, and the elements of the same topic will be grouped together. For example, the elements of point, line and surface types of water system data are organized into the same vector element dataset, and the point elements of village residence, village residence notes, township residence, township residence notes, county residence, county residence notes, municipal residence, municipal residence notes, and so on, are organized into a point note element dataset with text information. Then the corresponding projection transformation and data format conversion processing.
11.4.3.2 DEM Data Processing and Organization
The DEM data for this system build is generated directly in ArcInfo from the Terlkla (contour) layer in the base geodatabase, using the same resolution of 3″, and is organized and stored according to the raster dataset of the ArcSDE Geodatabase.
ArcSDE stores raster data in a similar way to how it stores geometric objects. When raster data is stored in the ArcSDE database, it is converted to an ArcSDE-specific format. In ArcSDE's system tables and user tables, raster data is represented as many small binary large objects (blobs) or slices (tiles), and a raster data field is added to the created business table, and the field name can be chosen arbitrarily as long as it conforms to the naming rules of the underlying database. Only one raster data field is allowed to be created in this table, and at the same time four other new tables are created with the names SDE-raster-9, SDE-blk-9, SDE-aux-9, and SDE-bnd-9, and the corresponding records are added to the table RASTER-COLUMNS. The pixel data of the actual image and its position is stored in SDE-blk-9 and the pixel size is stored in SDE-bnd-9.
11.4.3.3 TM and ETM+ Remote Sensing Image Processing and Organization
The results of 1:250,000 TM and ETM+ remote sensing image maps of the whole province are provided by the corresponding sub-themes of the project, and the subdivision and numbering of which are carried out in accordance with the provisions of GB/T13989, the planar coordinate system adopts the 1954 Beijing coordinate system, and the projection adopts the Gauss-Krüger projection. The TM or ETM+ data of the province will be transferred to GeoDatabase after mosaic splicing according to the accuracy of 1:250,000, and the organization and storage mechanism of ETM remote sensing image in ArcSDE Geodatabase is the same as that of DEM.
In addition, using ArcToolBox tool to load raster data, when inputting large data volume of remote sensing image data, a dialog box often appears, prompting the error message of insufficient disk space. In order to avoid this situation, this data library also use the ArcSDE comes with API functions, compiled a specific conversion program to solve the problem of large-volume remote sensing image data into the library.
11.4.3.4 Data Processing and Organization of Various Thematic Data
According to the requirements of the general design document of the project, the results of various thematic issues involve vector graphics, and their data format must be submitted in Arc/Info E00 file format. If the result data generated by other GIS systems are used, they must in principle be converted to the data format of Arc/Info EOO and then submitted. If the GIS system used cannot be converted to the data format of Arc/Info Coverage or EOO, the data exchange format specified in dxf or GB17798-1999 Geospatial Data Exchange Format VCT submission results. Among them, the data results submitted in the form of VCT must be submitted with the identification code or identification code corresponding to each point, line and face, and the identification code or identification code must be the same as the national standard or industry code corresponding to each thematic resource result map.
If other raster data formats are involved in the results of each topic, in addition to the original TM data, other remote sensing satellite data, aerial film data, and thematic interpretation images must be submitted in the common .TIFF format or the .IMG format of the ERDAS system, or the data exchange format specified in GB17798-1999 Geospatial Data Exchange Format (GDEF). The image data exchange in the Geospatial Data Exchange Format simply adds a text description file to the standard TIFF or BMP format.
After the spatial information involved in the above thematic results are converted into a unified file format, they can be processed according to the vector element dataset and raster dataset respectively in ArcSDE Geodatabase.
11.4.3.5 Metadata Processing and Organization
Each sub-database of the basic database for integrated remote sensing survey of land resources has its own metadata, including vector and raster data metadata content. It stores information about data sources, data layering, product attribution, spatial reference, data quality (data accuracy, evaluation), data, map margin aspects and so on. Metadata is mainly stored as text and HTML or SGML.
Metadata is also a type of data that is not different from other data in form. Metadata is in the form of a digital form consistent with metadata content standards and can be created, stored and used in a variety of ways. Text file is the most basic method, easy to transmit to the user; another method is to use the text link markup language (HTML) written in a hypertext file, or Extensible Markup Language (XML) way, the user can use the browser way (Netscape Navigator, Internet Explorer) to query them; there is also a way to use the Generalized Markup Language (SGML) to build metadata. Language (SGML) to create metadata (Wang, 2000).
11.4.3.6 Expansion of Logical Database
Expansion of logical database is one of the main features of the whole system, and its significance lies in the fact that users can customize their own spatial data sub-database according to the actual needs of application, combined with the thematic databases in the database (including the database of the current state of land use, the database of the main mineral resources, the database of the geologic hazards and environment, The database can be combined with the thematic databases in the database (including database of land use status, database of major mineral resources, database of geological hazards and environment, database of offshore islands, database of coastal zones, database of geological structure and crustal stability, and database of dynamic changes in key cities, etc.) to produce other thematic data with stronger application.