Fujian Surveying and Mapping Institute

Fuzhou, China

Fujian Surveying and Mapping Institute

Fuzhou, China
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Zhang F.,Fujian Surveying and Mapping Institute | Xu C.,Minjiang University
Journal of Geomatics | Year: 2011

Phase windup in GPS precise point positioning can not be eliminate or mitigate easily, so it is important to deal them with accurate correction models, or set residuals of them as unknown parameters. The phase windup error and it's correction models are discussed detailed. Numerical result shows the accuracy of PPP using the correction model.


Ye S.,Wuhan University | Zhao L.,Wuhan University | Chen D.,Wuhan University | Pan X.,Tianjin Institute of Geotechnical Investigation & Surveying | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2016

In real-time deformation monitoring applications, ambiguity cannot be quickly and reliably resolved under poor conditions using dual-frequency observations. In this paper, we analyze the single epoch ambiguity resolution success rate of GPS and BDS system under different calculating models. A new method based on triple-frequency BDS observations is proposed to fix the original ambiguity based on the TCAR (three-carrier ambiguity resolution. Sidereal day filtering based on observing domain reduces multipath errors in wide-lane observations under conditions where the original ambiguity cannot be fixed reliably. Real data is used to test the method, results show that the success rate and accuracy are improved in comparision to the dual-frequency models. A success rate of 100% was achieved using the wide-lane ambiguity resolution, and the RMS values for the wide-lane fixed solution reached 7 mm after filtering. © 2016, Research and Development Office of Wuhan University. All right reserved.


Liu Y.,Wuhan University | Ye S.,Wuhan University | Jiang P.,Wuhan University | Chen H.,Design Science | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2015

More linear combinations with longer wave-length and smaller noise can be formed with triple frequencies, which will accelerate ambiguity resolution. The TCAR and CIR methods are most representative, based on the no-geometry model but these approaches neglect information between satellites. In this paper, a geometry-based step by step ambiguity resolution method is presented, extra wide-lane ambiguities, two wide-lane ambiguities and narrow-lane ambiguities of two ionospheric-free combinations are fixed sequentially. An experiment with real BeiDou observation data demonstrated that for baselines within 10 km, nearly all the ambiguities can be fixed at a single epoch. ©, 2015, Wuhan University. All right reserved.


Liu Y.,Wuhan University | Ye S.,Wuhan University | Jiang P.,Wuhan University | Huang Z.,Southern Research Institute | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2014

As a consequence of a daily data processing strategy, an adjacent IGS final precise clock product displays discontinuity at the junction of two successive days. This will cause a jump in positioning results for the pseudo-range, and change all the related ambiguities. These non-integer cycle slips will require filtering to make them converge. In this paper, the magnitude of the jump of every satellite for a seven day cycle is investigated in detail. Then, based on the full discussion of the data processing strategy of the IGS center, the reasons for discontinuity and the precision of the final clock product are presented. Two counter measures are proposed: one is to insert the jump in the satellite clock datum into the IGS clock product; the other is to estimate the clock datum for adjacent days. Finally the results of the two processing strategies are presented.


Xia J.,Wuhan University | Sun M.,Qinghai First Institute of Surveying and Mapping | He S.,Fujian Surveying and Mapping Institute | Ye S.,Wuhan University
Journal of Geomatics | Year: 2013

The theory of equivalent observation is briefly introduced first in this paper,and on the basis of the mentioned theory, another but equivalent model of sequential least square model is proposed. The new model comes from two main following steps: first, last-epoch estimated parameters and their covariance are seen as virtual observations and corresponding variance of current-epoch parameters, so virtual observation equations can be formed immediately; then, the virtual equations are combined with current-epoch observation equations to estimate current-epoch parameters using least square method.


Jiang P.,Wuhan University | Ye S.,Wuhan University | He S.,Fujian Surveying and Mapping Institute | Liu Y.,Wuhan University
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2013

An exponent fading factor adaptive Kalman filter algorithm instead of standard Kalman filter is introduced to improve the ground-based GPS tomographic method of wet refractivity. Two different periods of GPS observation data and meteorological data from Hong Kong CORS are processed to determinate the 3D distribution of wet refractivity with tomographic method. The results show that this method can retrieve the wet refractivity vertical profile and 3D distribution precisely within a long tomographic procedure without any divergence.


Ai N.,Beijing Forestry University | Wei T.,Beijing Forestry University | Zhu Q.,Beijing Forestry University | Zhao X.K.,Beijing Forestry University | And 3 more authors.
Physical Geography | Year: 2015

The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion in China. The Chinese government initiated the project "Grain-for-Green" for soil erosion control in 1999, with significant effect. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; therefore, the aim of this research was to investigate the effects of these four factors on runoff and soil loss at the runoff-plot scale over five years and use the Gray relational analysis methods to compare the impacts of these factors. Five runoff-measuring sites were established in five different vegetation types. The results show that the relative impacts of the four factors on runoff were: rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation. We also analyzed the weights of these four factors on runoff and sediment yield during the wettest year alone. For that year, the relative weights of the factors on runoff were topography > rainfall > soil > vegetation, and the relative weights of the factors on sediment yield were runoff > soil > rainfall > topography > vegetation. © 2016 Taylor and Francis.


Luo W.,Fujian Surveying and Mapping Institute | Luo W.,Indiana University | Zhang H.,Indiana University | Zhang H.,University of Louisville
Proceedings - 2015 IEEE International Conference on Big Data, IEEE Big Data 2015 | Year: 2015

In this study we analyzed a series of LiDAR point clouds acquired over Taijiang district (part of Fujian province, China). The objective was to detect and extract water surface area from individual LiDAR point cloud, in a parallel means. To this end, interactive visualization of fine-grained data, global cluster algorithms, and statistical investigation were applied. We first rasterized point clouds into a series of matrices; then a density based algorithm (DBSCAN) allowed us to isolate the single cluster features which represented the water surfaces. Base on the clustered features, our framework created polygons for further quantitative assessments. The computations for the cluster analyses and their parallelized versions were carried out using R free software for statistical computing and graphics. © 2015 IEEE.


Ai N.,Beijing Forestry University | Wei T.,Beijing Forestry University | Zhu Q.,Beijing Forestry University | Zhao X.K.,Beijing Forestry University | And 2 more authors.
Physical Geography | Year: 2016

The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion in China. The Chinese government initiated the project “Grain-for-Green” for soil erosion control in 1999, with significant effect. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; therefore, the aim of this research was to investigate the effects of these four factors on runoff and soil loss at the runoff-plot scale over five years and use the Gray relational analysis methods to compare the impacts of these factors. Five runoff-measuring sites were established in five different vegetation types. The results show that the relative impacts of the four factors on runoff were: rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation. We also analyzed the weights of these four factors on runoff and sediment yield during the wettest year alone. For that year, the relative weights of the factors on runoff were topography > rainfall > soil > vegetation, and the relative weights of the factors on sediment yield were runoff > soil > rainfall > topography > vegetation. © 2016 Taylor & Francis


Xie R.,Beijing Forestry University | Xie R.,Fujian Surveying and Mapping Institute | Wu X.,Beijing Forestry University
Journal of Geographical Sciences | Year: 2016

Changes in soil organic carbon (SOC) in rangelands has been extensively investigated. Grazing in outlying rangeland areas has caused severe impacts on ecosystem functions. To reveal the effects of grazing on SOC, we evaluated the grassland in Xilin Gol League, Inner Mongolia, China. Grazing intensity was determined by using two image sets of vegetation index with normalized differences in grazing periods (July 12th and 28th). The range of variation in vegetation index was then used to measure the grazing intensity. The SOC storage and density were obtained by conducting experiments on field soil samples. Results showed that 1) the grazing intensity in Xilin Gol League declined gradually from west to east; by contrast, the spatial distribution of SOC density increased gradually. 2) As grazing intensity increased, the carbon storage of rangeland decreased evidently. Minimum carbon storage was observed in grasslands classified under extreme overgrazing; by comparison, maximum values were found in areas classified under light overgrazing to moderate grazing. 3) The estimated soil carbon storage was 8.48 × 1011 kg, and the average carbon density was 4.08 kg/m2. Our research demonstrated that grazing intensity likely affects soil carbon. Moderate grazing is an optimum strategy to maintain carbon storage and ensure sustainable grassland utilization. © 2016, Institute of Geographic Science and Natural Resources Research (IGSNRR), Science China Press and Springer-Verlag Berlin Heidelberg.

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