(China Land Survey and Planning Institute, Beijing, 100035)
On the basis of analyzing and expounding the basic concepts, functions, existing acquisition methods and existing problems of national land and resources information, this paper puts forward the technical difficulties, technical system and basic conditions for obtaining and updating national land and resources information to meet the macro-management objectives of national land and resources. The research shows that it is urgent to establish a nationwide technical system for obtaining and updating land and resources information. Its goal is to establish a nationwide background database and dynamic database of land and resources investigation and monitoring, form a technical system of land use/cover information acquisition and dynamic updating based on multiple information support, and provide more effective data support for macro-management of land and resources. All the conditions of the national land and resources information acquisition and updating technology system have been met, and the construction of this system is of strategic significance to the sustainable development of the country.
Keywords: information acquisition and update; Nationwide; Land resources; Background database
1
Land resource information reflects the regional land use/coverage status, which is one of the important contents of geospatial information and has the characteristics of time scale and spatial scale. Different management objectives and methods determine the different spatial scales of land resources information needed for management. Obtaining the land resource information of the corresponding scale is the basis for land resource management institutions at all levels (see figure 1). National land and resources information can be understood as land use/land cover data information that reflects the national coverage (or key areas) and meets the decision-making at the national level. The accuracy requirement is between 1:65438+ 10,000 ~1:4 million, and the amount of information can meet the requirements of national macro-management of land resources for cultivated land, construction land and ecological protection land.
Figure 1 Requirements of Land Resource Management on Data Spatial Scale
The methods of obtaining national land resources information usually include sampling survey and comprehensive survey, and the implementation methods include top-down survey mode and bottom-up survey mode. In the 1980s, the mid-1990s and the third day of the 20th century, China Academy of Sciences made use of TM/ETM ++ images to conduct national land use/land cover remote sensing surveys, and basically established the national macro-spatial dynamic database of remote sensing of resources and environment [1 ~ 2]. Since 1999, the Ministry of Land and Resources has carried out remote sensing monitoring of land use dynamics in cities with a population of more than 500,000, which has provided a strong guarantee for land law enforcement [3]. The above-mentioned national surveys based on remote sensing technology are all top-down sampling surveys. At present, in terms of land and resources investigation and management, the main body of China's land and resources investigation technology system still adopts the bottom-up investigation method, that is, the nationwide data are collected and processed by local land management agencies at all levels, and then summarized step by step by county-city-province-country. The main representative surveys include the national detailed land survey and the annual land change survey [4-5]. In comparison, the top-down method has the advantages of fast investigation speed and low cost, and can avoid artificial data deviation, but the details of the obtained data are limited; The bottom-up survey method can obtain more comprehensive data, but the survey period is long and the cost is high, and the quality of the survey results is greatly affected by human activities. In recent years, with the rapid development of information technology, China's ability to obtain land and resources information by using "3S" technology has been continuously enhanced [6 ~ 7]. The technical system of land and resources information acquisition, which integrates land use change investigation, county-level land use database construction and urban land use dynamic remote sensing monitoring, has been continuously improved, which has met the current national demand for macro-management of land and resources to some extent. However, due to China's vast territory and limited by economic and technical conditions, especially the lack of in-depth understanding of the national objectives of land and resources management, there are still many problems in obtaining national-scale land and resources information in China. For example, the authoritative background database of national land and resources spatial information has not been established, the research on national land and resources classification standards and information collection methods suitable for rapid acquisition of remote sensing technology information is not deep enough, the effective comprehensive data updating mechanism necessary for farmland supervision has not been put on the agenda, and the effective information of national land and resources urgently needed for macro-management of land and resources is seriously lacking.
On the basis of making full use of the first national land resources survey, the dynamic remote sensing monitoring of land use in cities with a population of more than 500,000, the annual land change survey, the construction of land use database at 1∶ 1 10,000 county level, and the updating survey of basic data, this study adopts a combination of top-down and bottom-up methods, with medium and high resolution remote sensing images as the basic data. With multi-scale data synthesis, multi-data fusion and data sampling as the core, a nationwide technical system of land and resources information acquisition and rapid updating is constructed to achieve the goal of providing continuous information and technical support for macro-management of land and resources.
2 objectives and technical difficulties
2. 1 target
The construction goal of national land and resources information acquisition and updating technology system includes three aspects: establishing national land and resources information base, forming national land and resources information background database, constructing technology system, and integrating national land and resources data updating technology system under various technologies. The specific content is:
(1) Establish a national land and resources information database and update it every five years. On the basis of various historical data, the national background database of land and resources information is established by using medium and high resolution remote sensing images (TM/ETM++, SPOT, China-Brazil resources satellite, etc.). ) is the main source of information, and it is updated every two to three years and every five years in key areas throughout the country. The national scale land and resources information background database includes remote sensing orthophoto data, land use/coverage vector data, administrative division vector data, land use zoning and other basic background data, which can meet the needs of national scale cultivated land protection, basic farmland protection, construction land monitoring and ecological environment protection.
(2) Forming a technical system for building a national land and resources information background database. Based on the national detailed land survey data that ended in 1996, with TM, ETM++, China-Brazil resources satellite and SPOT image data in this period as the background, the detailed land survey data and historical data and materials such as 1∶ 1 10,000 land use vector data of "Digital Land" project are fully utilized, and through data extraction, data mapping synthesis and knowledge-based information, Establish a vector database with newly added land use/cover classification as the main content and a multi-source remote sensing orthophoto database to form a technical system for building a national land and resources information background database.
(3) The technical system of land and resources data updating integrating various technologies. In-depth study and application of multi-temporal remote sensing image comparative classification and interpretation methods [8], land cover classification under the control of land use vector map spots [9], multi-temporal data expression, multi-temporal data mining and knowledge discovery and other key technical issues, forming a national land and resources information updating technical system based on multi-technology integration, and providing technical support for national land and resources data updating.
2.2 Technical difficulties
(1) The construction target of national land and resources information acquisition and updating technology system is determined. The purpose of obtaining national land and resources information is different from the comprehensive land use survey and database construction carried out by land and resources management agencies at all levels for daily land and resources management, and it is also different from the high-resolution image remote sensing monitoring of urban land use dynamics in land law enforcement. Research purposes: To establish a national technical system for obtaining and updating land resources information, and to build a national background database and dynamic database of land resources information, so as to provide timely information on the quantity, quality and distribution of important land resources such as cultivated land, construction land and ecological land for the Ministry of Land and Resources, and to serve the participation of land resources in the formulation of macro-control policies for the national economy. Serve the central government to make social and economic sustainable development decisions and provide national land and resources information for scientific research.
(2) The information classification, accuracy requirements and results of the national large-scale land and resources survey are coordinated with relevant surveys. Modern remote sensing technology is the core of obtaining national land and resources survey information, and its information classification should meet the needs of national land and resources supervision as much as possible in principle. At the same time, we should fully consider the ability of using remote sensing data sources to identify land use/land cover types, foster strengths and avoid weaknesses, and reduce a lot of field investigation and verification work. This study focuses on the important land resources such as cultivated land, construction land and ecological land. In principle, national land information classification focuses on land use/land cover classification with land cover as its main feature, rather than adopting traditional land use classification standards. The accuracy of national scale land and resources information is based on remote sensing images between 10 ~ 30m, the survey accuracy is 1:65438+ 10,000, and the national data accuracy is1:500,000. The classified data of national large-scale land resources survey are consistent with other land resources surveys in important types such as cultivated land and construction land, and other types are only reference data.
(3) The sources of background information and comprehensive information can be quickly extracted. In view of the importance of background data, we can choose the background data of national land resources survey information as basic data, and make full use of county-level1:50,000 land use grid map, 1: 1 10,000 "digital land" project database, existing TM, ETM++ and so on. Through data extraction, data mapping synthesis, knowledge-based information extraction and data mining technology, vector database and multi-source remote sensing orthophoto database with new land cover classification as the main content are established.
(4) Using high-resolution remote sensing images for data sampling statistics and verification technology. In order to improve the accuracy of land resource information acquisition and reduce the workload of field investigation as much as possible, it is necessary to select a certain area as the transect after obtaining the comprehensive information of land use/cover by using medium and high resolution remote sensing images, and make full use of the dynamic monitoring results of urban land use-high precision remote sensing orthophoto as the basis for inspection standards and data interpretation verification and correction, and establish the conversion coefficient of land use/cover classification data of medium and high resolution images.
(5) Using multivariate information mining technology to update information quickly. Using early land use data, topographic data, soil and vegetation data can effectively improve the accuracy of land use dynamic remote sensing monitoring change discovery and type identification, which has important practical application value. The comprehensive application of various background information related to geoscience for data mining can realize the rapid update of land and resources information nationwide.
3 technical route
The technical characteristics of this study are technical comprehensiveness and objective effectiveness. The comprehensive performance of the technology is as follows: it will comprehensively apply a variety of remote sensing data, county-level land use data, national/kloc-0: 500,000 land use data, Chinese Academy of Sciences system land use data and national land use change data, and take remote sensing technology, multivariate data fusion, data sampling statistical verification and data mining as the core technologies to form a multidisciplinary land use/cover information acquisition and updating technology system. The objective validity is as follows: based on land use/cover classification, interpretation signs are mainly established by existing knowledge and information; The verification of classification results mainly depends on the high-resolution images of typical sample areas, making full use of a large number of data accumulated by dynamic remote sensing monitoring for many years, and not paying attention to field verification to reduce workload. The main technical route mainly includes five aspects: ① research on the classification of land and resources information, data sources and survey accuracy at the national scale; (2) obtaining the background information of full coverage land resources supported by multiple information; ③ Using high-resolution remote sensing images to check and analyze the interpretation data of typical transects; ④ Using multivariate information mining technology to update information quickly; ⑤ Comprehensive information application and service. (See Figure 2 for the overall technical roadmap).
Fig. 2 Structure of multimedia spatial database system
4 working basis and supporting conditions
4. 1 A large-scale remote sensing monitoring of land use dynamics was carried out.
China's land and resources system has carried out large-scale remote sensing monitoring of land use dynamics, and the organization method and workflow of investigation and monitoring are becoming more and more mature and perfect. For example, from 1996 to 1997, the former State Bureau of Land Management used TM and SPOT data to investigate and monitor the urban expansion of 1 19. From 1999, the land and resources survey project began to monitor land use changes in cities with a population of more than 500,000 by using TM, ETM ++ and SPOT data. After 2002, the remote sensing monitoring project began to use the high-precision 2.5-meter SPOT image as the main remote sensing data source, which greatly improved the remote sensing monitoring accuracy. In addition, the new round of land resources survey has begun to update the basic maps and data of land use at county level in China by using SPOT, IKNOS, IRS, Quick-Bird and aerial remote sensing data. In 2002, the Ministry of Land and Resources started the remote sensing monitoring project of resources and ecological environment around Beijing for the first time. This project uses TM or ETM ++ and SPOT remote sensing data to monitor the land use, land degradation and ecological environment construction in 52 counties around Beijing [10]. The above practice of land use investigation and monitoring based on remote sensing provides valuable experience for the construction of national land resource information acquisition and updating technology system.
4.2 In-depth research on remote sensing monitoring technology of land resources.
China has carried out in-depth research on remote sensing technology of land resources in many aspects. In the research of remote sensing monitoring technology, the "Demonstration Research on Dynamic Monitoring Technology and Method of Land Use" initiated the industrial process of rapid monitoring of land use change by using SPOT and TM remote sensing data, realized remote sensing monitoring of specific plots, quickly found land cover/use changes, developed image correction technology with image graphic array instead of single control point and satellite image correction technology without DEM support, and improved the information extraction method of land use change by combining automatic means with manual visual interpretation. In the research of imaging spectrum technology, the national 863 project "Application of imaging spectrum technology in land dynamic monitoring" can make use of the high spectral resolution of imaging spectrum technology to increase the degree and accuracy of land use type identification. The research on land type identification and land quality monitoring using imaging spectrum technology is innovative and has important theoretical value [1 1]. In the research on the rapid database construction of county-level land use/land cover, the technicians of our institute participated in the land use remote sensing monitoring project organized by Chinese Academy of Sciences for many times, and conducted in-depth research on the dynamic database construction of county-level land use/land cover supported by multi-source remote sensing data in typical areas [8], and accumulated rich experience. The technology required for this project is basically available, and only further technical integration is needed.
4.3 The system construction has a solid data foundation.
Large-scale land and resources survey project has achieved rich data results, providing a solid data foundation for the construction of national land and resources information acquisition and updating technology system. At present, the detailed land survey of more than 2,000 counties has been completed at the national level, and a large number of original data have been accumulated in the construction of1∶ 50,000 county-level land use grid library, which provides detailed information for national background remote sensing interpretation. The land use dynamic remote sensing monitoring project completed the land use dynamic remote sensing monitoring data set from 1999 to 2004, and obtained more than 700 satellite TM data, more than 2,300 SPOT 1/2/4 satellite data, 5 13 SPOT5 satellite data, 5 resource 2 data, 6 SAR data and 630 aerial photos. The investigation and evaluation project of cultivated land reserve resources has completed the construction of two databases: the database of land resources investigation and evaluation in the western development and the database of cultivated land reserve resources investigation and evaluation in China. The basic map and data updating project of land and resources has completed the data updating results of pilot cities such as Nanhai District, Foshan City, Guangdong Province and Ten Districts of Guangzhou City. The national land use database construction project has achieved land use database results in more than 1000 counties. These data results have laid a solid data foundation for the construction of national land and resources information acquisition and updating technology system.
4.4 Basic software and hardware system construction
Through years of efforts, the land data storage hardware, basic software (Oracle 10 g, Unix) and GIS software for data integration in the national land data center basically meet the requirements, the land data storage network system has been initially established, and the development of the land data storage application management system will be completed soon. The National Land Data Center also actively participated in the construction of science and technology sharing of the Ministry of Science and Technology. The land data sub-center is under construction and will become one of the three sub-centers of the land and resources science data center. In recent years, China Land Survey and Planning Institute has successively launched development projects such as land remote sensing monitoring data integration application, land use data quality inspection software and land data warehousing management system. These software systems have the function modules of data quality check, data integration and integrated management, which can integrate data resources in batches, which will facilitate the data integration and information mining of national land and resources information acquisition and information update, and greatly improve work efficiency.
5 Application prospect and prospect
China is a developing country with a large population. The sharp decrease of cultivated land resources, exhaustion of mineral resources, energy shortage and deterioration of ecological environment have become the core issues affecting the sustainable development of the country. In order to implement the strictest farmland protection policy and the decision of the CPC Central Committee to effectively participate in the macro-control of the national economy by using land resources, it is of great practical and long-term significance to study and build a nationwide technical system for obtaining and updating land resources information. The construction of national land and resources information acquisition and updating technology system will change the macro-management mode of land and resources at the national level, provide more accurate and objective data for the state to use land and resources for macro-control of the national economy, change the passive situation that national land and resources lack spatial data and farmland supervision relies too much on reporting statistical data step by step, and also effectively evaluate the authenticity of local reported data. With the limited continuous capital investment of the country, the land resources information needed by the national macro-decision will be provided continuously. The state-level land and resources information acquisition and dynamic updating technology system can also provide important information such as ecological background conditions and dynamic changes of land and resources necessary for ecological environment protection, which is conducive to establishing a harmonious economic and social development model of coordinated development between man and nature. National scale land and resources information can also be provided to agriculture, forestry, environmental protection, planning and other departments for use. In addition, national-scale land and resources background data and dynamic data are also important basic data for research in geoscience, environment, humanities and other related fields, which can directly participate in scientific data sharing and serve related scientific research.
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