Soil and water conservation monitoring; Remote sensing technology of soil erosion
With the enrichment of remote sensing image resources and the improvement of processing technology, the characteristics of remote sensing image such as wide coverage, fast cycle, high resolution and rich information make remote sensing technology play an increasingly important role in the field of soil and water conservation monitoring. In recent years, with the development of remote sensing technology, especially the high spatial resolution remote sensing satellite image has entered the practical stage, its application in soil and water conservation planning, management and supervision has been paid more and more attention, and its macro, rapid and objective advantages have been fully exerted, which has become an important means of soil and water loss monitoring. 1. Selection of remote sensing data The occurrence and development of soil erosion is a process of temporal and spatial change, and its monitoring and evaluation need to adopt different scales according to different purposes. Meteorological satellite images have the characteristics of high temporal resolution, large monitoring range and low data processing cost, but their spatial resolution is low, and the information reflected by pixels has a large regional mixture, which is suitable for large areas with uniform vegetation coverage, slope and surface composition. Resource satellite has the characteristics of multi-band and multi-phase, and its spatial resolution is relatively high, which can effectively obtain more accurate surface information and provide data support for soil erosion information extraction and model analysis. However, the repeated observation period in an area is long, and the required information is often not obtained in the critical period. In order to meet the requirements of time resolution and spatial resolution of soil and water conservation monitoring, information from different sources (including remote sensing and non-remote sensing) is usually combined to improve the data source accuracy of soil and water conservation monitoring from different angles (see figure 1). 2. Extraction of soil erosion information Using remote sensing technology to extract soil erosion information is based on satellite images as the main information source, 1:65438+ topographic map and1:250,000 digital map as the basic working base map, and 1: 100 and1:50,000 topographic map. Combined with various professional maps (such as geological map, topographic map, vegetation map, soil map, land use map, etc.). ), hydrometeorological data and other statistical data, with professional remote sensing image processing, computer-aided human-computer interaction interpretation, GIS spatial analysis and other technical means, combined with field route survey and typical quadrat survey, on the basis of establishing interpretation marks, make full use of multi-spectral multi-source image processing technology and expert experience to realize erosion types and erosion grades.
3. Conclusion Remote sensing image data can be obtained by aviation and aerospace means, and the development trend of soil erosion can be monitored in real time. With the support of geographic information system, the trend of soil erosion can be analyzed, and the results can be transmitted to decision-making departments in the form of intuitive graphics, images and charts, which is an important basis for formulating countermeasures for soil erosion and soil and water conservation. Figure 1 Multi-source remote sensing data preprocessing and data synthesis workflow II. Remote sensing dynamic soil and water conservation monitoring analysis Remote sensing dynamic soil and water conservation monitoring is to extract change information from remote sensing data in different periods in the same area by using the multi-sensor and multi-temporal characteristics of remote sensing. The periodicity and continuity of remote sensing information provide the possibility for dynamic monitoring of soil and water conservation. Using real-time remote sensing images to monitor the annual dynamic change of soil erosion intensity; Analyze the total amount of soil erosion and its annual change trend, the dynamic change trend of vegetation resources, the benefits of engineering measures and the benefits of forest and grass planting measures; Early warning of areas with serious soil erosion and deteriorating ecological environment; Through the analysis and evaluation of the data, the announcement of soil and water conservation status is issued regularly. 1. The characteristics of dynamic monitoring of soil and water conservation by remote sensing are as follows: firstly, various methods are adopted, including visual interpretation, computer image processing and their combination; Second, the spatial scale of monitoring is wide, from a typical small watershed to the whole watershed and even the whole country; Third, the monitoring time span is large, from several years to decades. 2. Dynamic monitoring process of soil and water conservation by remote sensing. The application of remote sensing image in soil and water conservation monitoring is mainly to monitor the change of soil and water loss, the authenticity and accuracy of soil and water conservation survey data, supervise the implementation and progress of soil and water conservation planning, and provide scientific basis for national economic construction and development. The monitoring function of soil and water conservation mainly includes the following six aspects: surface erosion monitoring, gully erosion monitoring, hydrological factor monitoring, other monitoring, soil erosion cause analysis and soil erosion hazard prediction. (1) data acquisition
The factors affecting soil and water conservation are comprehensively analyzed, including land classification, soil erosion type, erosion intensity, landform type, parent rock type, vegetation coverage and slope attribute. Combined with the application characteristics of remote sensing technology, data are collected from three aspects: ① remote sensing image data (TM, SPOT); ②1:50,000 topographic map, land use classification map, administrative division map, soil erosion map, etc. (3) Detailed survey data of the monitoring area based on words and data sheets. (2) Monitoring the workflow
Remote sensing dynamic soil and water conservation monitoring technology is mainly to combine and fuse remote sensing data in different periods, extract the change information of land use, and check the monitoring change information by combining field investigation and detailed change investigation data. The inspection methods of point-by-point comparison of key areas and general regional statistical comparison are adopted to repeatedly check and modify the information extraction results until the accuracy requirements are met. Finally, the special reports of soil erosion in various formats are generated, the future changes of soil erosion are predicted through various statistical analysis, and the special information of soil erosion is extracted to generate various statistical charts. Including the following three aspects: first, the generation of special reports, second, statistical analysis, and third, the generation of statistical charts.
Fig. 2 Flow chart of soil erosion information extraction
Figure 3 Flow chart of soil erosion information extraction The flow chart of dynamic monitoring is shown in Figure 3. 3. Evaluation of monitoring accuracy of soil and water conservation Monitoring accuracy is one of the important technical indicators of soil and water conservation monitoring, and monitoring methods and information sources are the main factors affecting monitoring accuracy. According to the latest land use status map, the field measurement is carried out with GPS receiver, and for a small experimental area, the change information points of more than 5 pixels are checked one by one for accurate positioning; Carry out sampling inspection on a large-scale monitoring area, and finally make statistics on the attributes, areas, precision comparison and other data of dynamic change points. 4. Conclusion With the support of GPS and GIS, the current situation of land use can be dynamically monitored by using high technology, and soil and water conservation can be dynamically monitored by using existing monitoring data, maps and the latest satellite remote sensing information, so as to grasp the latest dynamic changes of soil and water conservation in time; The comprehensive analysis of spatial remote sensing data and other professional data has improved the depth of remote sensing technology in the application of water conservancy informatization, provided scientific basis for the formulation of national water and soil conservation ecological environment policies, the regular release of water and soil conservation information, the macro-decision of leaders at all levels, the supervision and law enforcement of water and soil conservation, and the scientific planning and implementation of governance measures, and is an effective measure and technical support for realizing the transformation from traditional water and soil conservation to modern water and soil conservation. At the same time, the cost of completing the national soil erosion survey with the least manpower and material resources is one thousandth or one thousandth of that of the conventional method. The results of remote sensing soil erosion investigation have important application value and social benefits for soil and water conservation planning and land resources improvement.