Near-far effect mitigation method using pseudolite signal acquisition

In this paper,a new idea based on pseudolite signal acquisition method aiming to mitigate the near-far effect problemin the satellite positioning is proposed.After analyzing the signal capture principle based on coherent integration and non-coherentaccumulation,the cross-correlation interference of strong and weak signals is eliminated by means of normalization of reconstructedstrong signal and judgement of the characteristics of the peak value,which can avoid the near-far effect of the pseudolitesignal.It can also estimate all the strong signals without any additional hardware.By building an indoor pseudolite positioningsystem,the capture performance becomes better based on improved acquisition algorithm compared with that based on thenon-coherent accumulation after coherent integration algorithm.The near-far effect is restrained effectively and the probabilityof weak signal detection is increased by25%.

Combined GPS/GLONASS Data Processing

To obtain the GLONASS satellite position at an epoch other than reference time,the satellite’s equation of motion has to be integrated with broadcasting ephemerides.The iterative detecting and repairing method of cycle slips based on triple difference residuals for combined GPS/GLONASS positioning and the iterative ambiguity resolution approach suitable for combined post processing positioning are discussed systematically.Experiments show that millimeter accuracy can be achieved in short baselines with a few hours’ dual frequency or even single frequency GPS/GLONASS carrier phase observations,and the precision of dual frequency observations is distinctly higher than that of single frequency observations.

High Sensitivity Acquisition Algorithm for DSSS Signal with Data Modulation

In direct sequence spread spectrum communication both for satelliteto-ground and inter-satellite links, the system constrains due to radio frequency spectral occupation, channel data throughput and link performances in terms of data channel coding which might result in a signal structure where the symbol duration is shorter than the pseudo code period. This can generate some difficulties in the DSSS signal acquisition due to the polarity inversion caused by the data modulation. To eliminate the influence due to polarity inversion, this paper proposes a novel acquisition algorithm based on the simultaneous search of the code phase, data phase and Doppler frequency. In the proposed algorithm the data phase is predicted and the correlation period for the coherent integration can be set equal to the symbol duration. Then non-coherent accumulation over different symbol is implemented in order to enhance the acquisition algorithm sensitivity; the interval of non-coherent accumulation is the least common multiple between the symbol duration and the pseudo code period. The algorithm proposed can largely minimize the SNR loss caused by data polarity inversion and enhance acquisition performance without a noticeable increase in hardware complexity. Theoretical analysis, simulation and measured results verify the validity of the algorithm.

MONITORING THE DIFFUSION OF SUSPENDED SEDIMENTS AND STABILITY OF TIDAL RADIAL SAND RIDGES AREA USING MULTI-SATELLITE REMOTE SENSING DATA

Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with the submarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huanghe River changed its course and flowed northward into the Bohai Sea.

Research on High Resolution Satellite Image Classification Algorithm based on Convolution Neural Network

Artifi cial neural network is a kind of artificial intelligence method to simulate the function of human brain, and deep learning technology can establish a depth network model with hierarchical structure on the basis of artificial neural network. Deep learning brings new development direction to artificial neural network. Convolution neural network is a new artificial neural network method, which combines artificial neural network and deep learning technology, and this new neural network is widely used in many fields of computer vision. Modern image recognition algorithm requires classifi cation system to adapt to different types of tasks, and deep network and convolution neural network is a hot research topic in neural networks. According to the characteristics of satellite digital image, we use the convolution neural network to classify the image, which combines texture features with spectral features. The experimental results show that the convolution neural network algorithm can effectively classify the image.

Geological Evidence and Characteristics of Activity of the Wuhe-Mingguang Section of Tancheng-Lujiang Fault Zone in Late Pleistocene

As the most influential strike-slip fault in East China,the Tancheng-Lujiang fault zone draws scholars attention for its strong seismic activity. Nevertheless,most research has been conducted along segments in Shandong Province and Bohai Bay where huge earthquakes occur frequently. Meanwhile,it is generally believed that segments lying to the south of Huaihe River have been inactive since the late Quaternary and thus it is incapable of generating moderate or strong earthquakes. However,these understandings about the Tancheng-Lujiang fault have been questioned by our recent work for part of the fault south to the Huaihe River. Based on interpretation of high-resolution satellite images,detailed field investigations near Wuhe county and Mingguang City in northern Anhui Province and elaborate microstructure analysis, we come to the conclusion that the Tancheng-Lujiang fault zone mainly consists of four branches and at least one should be active since the late Pleistocene for the Wuhe-Mingguang section. This segment is monopolized by dextral strike-slip motion in late Quaternary. Different from obvious faults in bed rocks or consolidated sediments,the latest activity trace in Quaternary loose sediment revealed by trench excavation is not obvious or even invisible to visual observation. According to our recent work and previous studies, we call for more attention to be paid to invisible faults in young sediment and also suggest that more research be conducted along this seemingly placid segment.

Impacts of land-use change on ecosystem service value in Changsha,China

Changsha,a typical city in central China,was selected as the study area to assess the variations of ecosystem service value on the basis of land-use change. The analysis not only included the whole city but also the urban district where the landscape changed more rapidly in the center of the city. Two LANDSAT TM data sets in 1986 and 2000 and land use data of five urban districts from 1995 to 2005 were used to estimate the changes in the size of six land use categories. Meanwhile,previously published value coefficients were used to detect the changes in the value of ecosystem services delivered by each land category. The result shows that the total value of ecosystem services in Changsha declines from $1 009.28 million per year in 1986 to $938.11 million per year in 2000. This decline is largely attributable to the increase of construction land,and the conversion from woodland and water body to cropland to keep the crop production. In the five districts,there is $6.19 million decline in ecosystem service value between 1995 and 2005. Yuelu District has the highest unit ecosystem service value while Yuhua District has the lowest one. This may be attributed to the greater conversion from cropland and grassland to woodland and water body with the increase of construction land in Yuelu District. It is suggested that the increase rate of construction land should be controlled rigorously and the area of woodland and water body should be increased or at least retained in the study area.

Hygienic Quality of Fish Depending of Cadmium （Cd） and Lead （Pb） Content in Bottom Sediments of Water Reservoirs Kolinany

Analysis of bottom sediments in water reservoir Kolifiany from the aspect of Cd and Pb contents, the determination of observed heavy metal contents in different parts of carp body （meat muscle, liver and kidney） and the evaluation of hygienic status and suitability of fish meat for the human consumption were performed. For analysis, each tissue sample was dissolved in a solution of nitric acid p.a. （HNO3：HzO = 2：1）; sediment sample in solution of acids （HF-HNO3-HCIO4） and analyzed for presence of Cd, Pb by the atomic absorption spectrophotometer （AAS） Varian Duo 240FS and 240Z. Our results confirmed hygienic harmless of bottom sediments in water reservoir Kolifiany. The Cd, Pb contents in sediments represent no risk within their input into the fish organisms. The Cd content in fish meat is lower than maximum available amount given by legislative norms, and the contents of Pb in fish meat too. The results of Cd, Pb content determination in carp body confirmed that fish muscles belong to suitable foodstuff for the human consumption.

Properties of Fuzzy M-Semigroups with t-Norms

In this papr, we introduce the notion ofT-fuzzy M-subsemigroups of M-semigroups by using a t-norm T and obtain some interesting properties. Further we show that the direct product of a T-fuzzy M-subsemigroup of R and a fuzzy M-subsemigroup of S is a T-fuzzy M-subsemigroup of M, Moreover, we prove that T-fuzzy M-subsemigroup of M is exhibited as the direct product of T-fuzzy M-subsemigroups of R and S respectively.

Snow Information Abstraction Based on Remote Sensing Data： Taking the North of Xinjiang for Example

This paper proposes an applicable approach for snow information abstraction in northern Xinjiang Basin using MODIS data. Linear spectral mixture analysis （LSMA） was used to calculate snow cover fractions （SF） within a pixel, which was used to establish a regression function with NDSI. In addition, 80 snow depths samples were collected in the study region. The correlation between image spectra reflectance and snow depth as well as the comparison between measured snow spectra and image spectra was analyzed. An algorithm was developed for snow depth inversion on the basis of the correlation between snow depth and snow spectra in the region. The results indicated that the model of SF had a high accuracy with the mean absolute error 0.06 tested by 26 true measured values and the validation for snow depth model using another dataset with 50 sampling sites showed an RMSE of 1.63. Our study showed that MODIS data provide an alternative method for snow information abstraction through development of algorithms suitable for local application.

Feasibility study of inclined geosynchronous SAR focusing using Beidou IGSO signals

Dear editor,Geosynchronous synthetic aperture radar(GEO SAR)[1,2]has an inclined geosynchronous orbit of around 36000 km,which leads to its short revisit time of around 24 hours and a wide coverage of up to approximately one third of the Earth surface.Its long integration time guarantees the fine resolution.Thus,GEO SAR owns the promising capability of providing images with the high resolution,

Separating impacts of vegetation change and climate variability on streamflow using hydrological models together with vegetation data

Vegetation information is seldom considered in lumped conceptual rainfall-runoff models.This paper uses two modified rainfall-runoff models,the Xinanjiang-ET and SIMHYD-ET models in which vegetation leaf area index is incorporated,to investigate impacts of vegetation change and climate variability on streamflow in a Southern Australian catchment,the Crawford River experimental catchment,where Tasmanian blue gum plantations were introduced gradually from 1998 till 2005.The Xinanjiang-ET and SIMHYD-ET models incorporate remotely-sensed leaf area index(LAI) data obtained from the Advanced Very High Resolution Radiometer(AVHRR) on board NOAA polar orbiting satellites.Compared to the original versions,the Xinanjiang-ET and SIMHYD-ET models show marginal improvements in runoff simulations in the pre-plantation period(1882-1997).The calibrated Xinanjaing-ET and SIMHYD-ET models are then used to simulate plantation impact on streamflow in the post-plantation period.The total change in streamflow between the pre-plantation and post-plantation periods is 32.4 mm/a.The modelling results from the two models show that plantation reduces streamflow by 20.5 mm/a,and climate variability reduces streamflow by 11.9 mm/a.These results suggest that increase in plantations can reduce streamflow substantially,even more than climate variability.