作者：徐存存

State Bureau of Surveying and Mapping recently hosted a national summit on the geographic information industry, the independence of our nation's first civilian high-resolution three-dimensional mapping satellite - on the 3rd of resources during the first half of the satellite will be launched in 2011. Satellite development has entered the initial stage, including the launch vehicle systems, ground systems and applications, including the construction of the other work of the various sub-systems are being stepped up, construction is progressing well.
Through the three-dimensional observation, the system can detect 1:5 million scale topographic maps, they can conduct the investigation and monitoring of land and resources, as well as agriculture, disasters, resources and environment in areas such as the provision of services.
Three-dimensional images in the future, the high mountains, steep valleys, the lighthouse stands, elevated bridge, the road rolling, angular houses, etc., will be true in your field of vision, the adoption of three-dimensional observations, system can detect 1:5 million scale topographic maps, land and resources to carry out investigation and monitoring, as well as agriculture, disasters, resources and environment in areas such as the provision of services.
The near future, China's first independently developed high-resolution three-dimensional mapping of the civilian satellite - on the 3rd of resources, China will fill a three-dimensional mapping of the blank in this field.

■ mapping function

All along, China's access to a variety of geo-spatial information, mainly through aerial photography measurements, but taken as a result of air affected by the weather and many other factors can not be effective in real-time access to the original image, so the high-resolution satellite remote sensing image urgency of the demand resources to solve the original Route satellite images lack the constraints of industrial development of China's geographic information bottleneck problem, but in the end it is how does a three-dimensional mapping?

Three-dimensional three-line array camera shooting
State Bureau of Surveying and Mapping, deputy director of land surveying and mapping, resource Route satellite projects director of the Office of孙承志, the resources Route 4 satellites were loaded with cameras, to take three-shot three-dimensional array. The so-called three-dimensional photography, that is, the three linear array camera in accordance with the forward-looking, face up, depending on the way after the order (one forward, one down, one after North Korea), so along a flight track of each satellite location There are three cameras to track the location of shooting the three, simulation of human eyes, before and after, as after, as the combination can form a three-dimensional images.
"In the high-resolution, which one of three three-line array camera down there to face up to the camera resolution of 2.5 meters, as the two cameras is around 4 meters, while a multi-spectral camera is better than 10 meters, it mainly in the blue , green, red and near-infrared band on four different objects to determine the properties of the ground and sub-mapping, the formation of color images. "Sun Chengzhi said.

Cycle to return to the same place for 5 days
Satellite in a fixed orbit flight, the Earth's north and south of latitude 84 degrees within the region to achieve seamless image coverage, from the Earth, the orbital inclination is about 6 degrees, which makes the film very close to the ground object attributes.
Satellite around the Earth after every round, there will be a point of view, it is covered by a global run time is 59 days, to the first 59 days to fly first return to the original track, so that the return of about 6 times a year. Objects themselves have a functional test before using this feature, if the special needs, it can be within five days filming on the same site, that is, re-visit period of 5 days. The design of the satellite life of 4 years.

■ critical applications

Measurement system can be 1:5 million scale topographic maps
Three days after the satellite resources, will be used mainly for measuring the basis of topographic maps and update the system as well as the difficulties in mapping and urban areas of mapping, the primary function for the 1:5 million scale for the three-dimensional mapping and digital video production, as well as 1 : 25,000 scale topographic maps, such as a greater part of elements of the update, will be established on the 3rd of satellite-based resources based on the production and update of geographic information technology application system.
"Our countries are the main means of mapping is aerial photography, aerial photography is currently imaging capability of China in the year 7-100000 km2, which is far unable to meet the needs of national economic development, but also the purchase of foreign commercial satellite images taken" ,Chen Chengzhi said, "Three satellite resources can effectively solve this problem, before imaging by computer image to a different location pairs, stripes removed, color modification and other pre-processing work, the final synthesis of a real three-dimensional measurement three-dimensional imaging model for three-dimensional mapping, this work will not overcome my shortcomings in the original satellite images. "

Agriculture, forestry, water and soil resources for the provision of information for decision-making
In the field of agriculture, resources satellite on the 3rd of all sizes for crop monitoring, agricultural engineering planning to provide high-resolution satellite images, survey of agricultural resources to meet the structural adjustment needs of the community. In the field of forestry, can make use of high-resolution images of forest pests and diseases, forest fires, such as conducting surveys and monitoring, timely provision of the scope and level of hazard information. Route satellite resources to provide three-dimensional image is also available vegetation, shadow, sand soil, light soil, such as remote sensing component maps, integration of image-rich color, texture clear.
In addition, the use of high spatial resolution satellite images can be extracted river basin land use and vegetation types of information, for a certain depth of the suspended solids and sediment distribution study of coastal waters of the estuary salinity and temperature measurements, the water body, such as chlorophyll concentration estimates provide an important supporting decision-making information.

Traffic to the area of environmental monitoring information
In the field of environmental monitoring, resource Route satellite for water pollution, river, the river water quality of the environment, a significant leakage of pollutants, the development of mineral resources of the ecological damage, urban ecology to provide continuous monitoring of a wide range of 5-10 m spatial resolution the rate of satellite images to achieve large-scale, all-weather, all at the time of the dynamic environmental monitoring.
In the transport sector, the resources on the 3rd of the high-resolution satellite images can be used for highways and railways, the preliminary design, traffic areas such as green design. In the transmission line project, the application of satellite image data to reduce the path length to avoid the adverse geological zone (such as landslides, avalanches, mudslides, strong earthquake area lots) to reduce house demolition, choose a better crossing points across the system significantly.

■ clear up the doubts of experts

Three advantages of satellite resources in which?
Reporter: Aerophotogrammetry the past compared to the advantages of satellite resources, on the 3rd where?
孙承志(Route resources satellite system engineering applications commander-in-chief): the past, aerial photography, a lot affected by the weather factors, such as rainy weather will not be able to shoot, resulting in only one imaging area 7-100000 km2, and is to count all the scales are, and on the 3rd of satellite resources to resolve this conflict, the use of functional return to the SAR unit can be avoided by the local weather factors other shooting options, and to generate a measurable the solid model, we can directly measured by computer model, not all of the field to conduct site surveys, we can collect accurate data. Achieved at the same time image processing and collation of the overall figures.

Model and whether the error between the physical features?
Reporter: The real model and whether the error between the physical features, how much error?
孙承志: real model and physical features exist between the error. Not the same error on different scales, the larger scale, the corresponding higher accuracy (smaller error). 1:5 million scale topographic elevation accuracy requirements of 5 meters, in some high mountain areas not yet reached such a high accuracy. 1:2.5 million on such a large-scale topographic maps, repair it and update can be measured, but to achieve such a high-precision, or more difficult. Route design resources satellite mapping scale is 1:5 million, 1:2.5 million Therefore, in carrying out measurement scale topographic maps can only meet some of the elements.

Construction progress of the satellite?
Reporter: Three satellite development resources need to go through several stages, the progress?
孙承志: Resources on the 3rd satellite developed in three phases, a total of 36 months. The first stage is the design phase of the program, a total of 6 months, on the 3rd of resources to the overall construction program of satellite engineering, and quality assessment of remote sensing image compression technology and other key indicators were studied. The second stage is the initial development stage, needs 18 months to complete, including the launch vehicle systems, ground systems and applications, including the construction of the other subsystems, the current project has progressed smoothly. The third stage is the production stage are like that kind of satellite production and the sky is the preparatory stage, the need for 12 months to complete all the work.