Applied Mechanics and Materials Vols. 239-240

Abstract: Due to the peculiar terrain of Alpine and Gorge Areas, traditional measuring method is difficult to adapt. We studied on a DEM generation method based on multi-baseline image sequences including an initial value estimate method of relative direction elements based on the perspective transformation and a matching method of image sequences based on virtual epipolar plane. The experiment proves that the convergence and accuracy of relative orientation can be effectively improved by estimating the initial elements with perspective transformation. In matching process, the matching points are transferred through virtual epipolar plane. So that, we can decreased calculation redundancy and obtain multi-overlap corresponding points rapidly and accurately.

Abstract: Spatial and temporal evolution of Pit deformation is the key issues of safety monitoring. Combined with GIS software and Vertical Mapper extension module, it used monitoring data and Kriging spatial interpolation method to generate the grid file and create digital subsidence model and draw subsidence contour and subsidence of section line, and time-effect and spatial effect analysis are realized in it. It reveals the spatial and temporal evolution of pit subsidence, and plays an important guiding significance to the security monitoring and early warning of pit.

Abstract: The precision of satellite positioning system depends largely on the numbers and geometric layout of the positioning satellite, the GDOP is one of the important parameters to measure the geometric layout of positioning satellites. From the perspective of GDOP, the relation between a different pseudo-satellite location and layout for the accuracy of the positioning system has been studied. For the positioning of the four pseudo-satellites, the simulation analysis of the relationship of the GDOP parameter changes with the pseudo-satellite longitude, latitude and location of the user. Studies have shown that different latitudes, the symmetrical distribution of the pseudo-satellite layout has good geometric accuracy; the same layout, the low-latitude, GDOP is less than the high-latitude; when the user moves in the regional variation in the geometric center of the pseudo-satellite layout, the GDOP values did not change and less than the value of the central region; at the same time, increasing the number of pseudo-satellite can reduce the GDOP value.

Abstract: We report on the time reference system of Compass global satellite navigation system and its interoperation with other GNSS’s. China has sent three satellites into geostationary orbit since 2000, and Compass Navigation Test System has been established. Compass time reference, named as BDT, is based on Atomic time, BDT is derived from the atomic clock ensemble in Compass ground control centre, and be traced to the international time, UTC. Interoperability is one of the most important aspect in the design of Compass timing system, a solution of time differences determination among BDT and other GNSS time scales are introduced in this paper.

Abstract: IBIS-L is an advanced remote monitoring system based on microwave interferometer, which integrates the interferometric survey, stepped frequency- continuous wave and synthetic aperture radar. IBIS-L can do high precise, large range, Omni-directional, real-time and remote displacement monitoring. The system can be widely applied in the monitoring of small-displacement changes in the dam, mountain, slope, surface, buildings and bridges[1]. The monitoring technology can get the displacement changes of every part, analyze the deformation mechanism and characteristics and forecast the disaster of dangerous region timely. So it can provide a reliable basis for disaster prevention, greatly reducing or avoiding the loss on people's life and property. We introduce the external deformation monitoring process and outcome of IBIS-L in a hydropower station dam and provide a useful reference for the application of IBIS-L to the similar dam.

Abstract: Flood disaster occurs frequently in Hejiang watershed, Guangxi province which causes huge economic and social losses. Remote sensing technique (RS) has the advantage of quickness, economy, objectiveness and large observation area. As is known to all, geographic information system (GIS) is good at analyzing and dealing with spatial data. Based on GIS, RS and hydrological and hydraulic models, flood disaster evaluation system of Hejiang river is developed which realizes the seamless connection of GIS platform with Xinanjiang model and Muskingum model. GIS system combined with necessary information obtained from remote sensing images could extract useful thematic information of flood disaster, which is meaningful to flood control and disaster relief of local authorities.

Abstract: Subsidence has been affecting Tianjin since 1960s. It posed comprehensive detrimental effects on natural environment, the economy and society. Considering the actual monitoring demand for land subsidence in Tianjin area, multi-baseline D-InSAR technique was studied. Using the multi-baseline DInSAR technique more interferograms can be generated, which is useful for retrieving the subsidence velocity accurately. And then regression algorithm and least square method are used to deal with the time series to get deformation result. In this paper, the multi-baseline DInSAR technique is used to measure the subsidence velocity in Tianjin area. It can be concluded that the algorithm is effective and feasible especially in the study area.

Abstract: Interferometric baseline plays a very important role in InSAR data processing, and it will directly affect the accuracy of interferometric result. Shuping area is covered by all of vegetation, so the coherence is very low. In Shuping area, it is very difficulty to generate clearly residue stripe to use the FFT method and to find natural coherence pixels points as GCP to refine the baseline to meet the need of monitoring the deformation accurately. But through CR stability phase information can be got. So It is also highlights to the apply CR in this region to refine the baseline parameters. In this article, the baseline got from coarse orbit file is regarded as initial value, and that got from precise orbit file is regarded as True. By comparing and analyzing the parameters of refined baseline with that of the precise baseline, it can be concluded that the refined method based on CRs is correct and feasible.

Abstract: A GNSS digital IF signal generator plays an important role in designing and testing modules and algorithms of a GNSS receiver. In this paper, a design of GNSS IF signal generator is described, which can integrate many kinds of GNSS simulated signal such as GPS, BeiDou, and GLONASS. This design can be configured by software flexibly to every kind of GNSS signal mode, so the complexity and cost of circuit are reduced. It can also avoid using the expensive simulated signal. The key logic circuits design is implemented in one FPGA chip. The implement method and simulation result on FPGA is shown at the last of the article.

Abstract: The paper introduces a design of wireless data acquisition and transmission terminal which takes Micro-controller ADuC848 as control center, combining with the Huawei GPRS/GSM wireless transmission module GTM900C. On the server computer designed GPRS data receiving software based on TCP/IP protocol. This system has succeeded in data acquisition and transmission in remote field. This paper describes the general scheme of the system from both hardware and software aspects and concretely introduces the method of remote data acquisition and transmission system, the final operation results of system are also given.