Table of Content

20 May 2016, Volume 45 Issue 5

Previous Issue    Next Issue

Concepts of Comprehensive PNT and Related Key Technologies

YANG Yuanxi

2016, 45(5):  505-510.  doi:10.11947/j.AGCS.2016.20160127

Asbtract ( )   HTML   PDF (1232KB) ( )  

References | Related Articles | Metrics

The core idea of comprehensive positioning, navigation and time (PNT) is the technique that uses all the available resources to provide PNT services in the whole area, including inside and outside door, air, space, under water and underground, which does not solely rely on the GNSS. The definition and basic concepts of the comprehensive PNT are presented. The possible signal sources are listed. The core technologies related to the comprehensive PNT are analyzed, including the integration of the multiple sensors and adaptive data fusion for multiple PNT signals. It is emphasized that the information of the comprehensive PNT should be from "multiple sources based on different physical principles", the control system should be operated by voluntary users based on cloud platform, the user terminals or sensors should be "deeply integrated" and the PNT information should be "adaptively fused" and serve mode might be based on cloud platform. The comprehensive PNT system should meet the robust availability, continuity, high accuracy and reliability with unified geodetic datum and time datum.

Piece-wise Linear Dynamic Adjustment for Gravity Network

WEI Shouchun, XU Jianqiao, ZHOU Jiangcun

2016, 45(5):  511-520.  doi:10.11947/j.AGCS.2016.20150362

Asbtract ( )   HTML   PDF (1320KB) ( )  

References | Related Articles | Metrics

Based on the status of the distribution and measurements in the national gravity network, a piece-wise linear dynamic adjustment model is introduced and applied to the analysis of the relative gravity observations in order to study the temporal gravity variations in mainland China. Compared with the traditional static adjustment model, more reliable temporal gravity variation characteristics can be given by the new model. To verify the validity of the model, it is processed that the gravity data from the national network and simulated data using the two methods, respectively. For the national gravity network, the mean difference of the rates of gravity changes obtained by the two adjustment methods is 13.4×10^-8 m·s^-2/a, with a maximum of 50×10^-8 m·s^-2/a. The precision of the dynamic adjustment is obviously better than the traditional static adjustment. For the simulated data, the rates of gravity change are compared with the theoretical ones at the same points. It is found that over 80% of the differences are less than 1×10^-8 m·s^-2/a from dynamic adjustment, and only two differences are larger than 2×10^-8 m·s^-2/a. In contrary, there are only 44.4% of the differences are less than 1×10^-8 m·s^-2/a from static adjustment, and 21% of the differences are larger than 2×10^-8 m·s^-2/a. Therefore, the piece-wise linear dynamic adjustment model can provide more reliable information of the temporal gravity changes compared with the traditional static adjustment model.

Test and Analysis of Downward Continuation Models for Airborne Gravity Data with Regard to the Effect of Topographic Height

LIU Min, HUANG Motao, OUYANG Yongzhong, DENG Kailiang, ZHAI Guojun, WU Taiqi

2016, 45(5):  521-530.  doi:10.11947/j.AGCS.2016.20150453

Asbtract ( )   HTML   PDF (1069KB) ( )  

References | Related Articles | Metrics

Downward continuation is an essential technical step of data processing in airborne gravimetry for further applications. It is known that the solution of downward continuation is uncertain due to its ill-posedness. So it has been a topic of general interest for many scholars at home and abroad in geodesy. The main purpose of this paper is to give 3 representative models for downward continuation including traditional inverse Poisson integration and two modern methods, and make a comprehensive comparison and analysis on their property and applicability among the different models. Ultra-high-degree geopotential model, local topographic correction and remove-restore technique are suggested to be used for regard to the effect of topographic height, and for the realization of downward continuation combining with a transformation from spherical to undulating surface. We pay our attention to the influence of surveyed data errors on the stability of downward continuation solutions. Theoretical analysis, simulated data and real numerical computations are carried out to evaluate the stability and accuracy of downward continuation models. And some useful conclusions are obtained. Under existing working conditions, the traditional inverse Poisson integration method can only be used to the continuation computation under 1 km due to the serious disturbing of surveying noise. Excellent computation stability can be achieved by using the band-limited spectrum and the geopotential model plus topographic correction methods. The two new models can be used to the downward continuation of airborne gravity data on 5 km height and 2' data resolution. And the accuracy of corresponding continuation solutions can be reach 2×10^-5 m/s². It can meet the requirements from different applications.

Generalized Residual Terrain Model and Its Application in Regional Gravity Field Approximation

WU Yihao, LUO Zhicai, ZHOU Boyang

2016, 45(5):  531-537.  doi:10.11947/j.AGCS.2016.20150219

Asbtract ( )   HTML   PDF (16392KB) ( )  

References | Related Articles | Metrics

We studied the so-called non-harmonic problem in residual terrain model (RTM) and compared the RTM corrections based on prisms and tesseroids. Moreover, we proposed the generalized RTM based on tesseroids, together with which the regional gravity field was modeled based on Poisson wavelets basis function by using heterogeneous gravity data sets. The results show that the RTM correction based on prism integral has a poor performance in mountainous regions, which may introduce errors with the magnitude of several mGal. Thus, we suggest using RTM based on tesseroids, which lead to a better approximation of the topography. Compared to original residual terrain model,the generalized one leads a better approximation of the regional gravity filed at the high-frequency part caused by local topographical variation.

Establishment of Absolute Gravity Datum in CMONOC and Its Application

XING Lelin, LI Hui, LI Jianguo, ZHANG Weimin, HE Zhitang

2016, 45(5):  538-543.  doi:10.11947/j.AGCS.2016.20140653

Asbtract ( )   HTML   PDF (1049KB) ( )  

References | Related Articles | Metrics

The high accuracy absolute gravity datum covered the Chinese mainland area is established by using absolute gravity measurement data of one hundred stations in CMONOC(Crustal Movement Observation Network of China), the accuracy of each station is better than 5.0 μGal/a. The high accuracy gravity datum can be used for relative gravity measurements in adjustment, and the real gravity value can be determined from relative gravity measurement data of adjustment by using the gravity datum to avoid distortion of the real figure of gravity change. The trend of absolute gravity change from several observations at Chengdu station shows that the secular trend of gravity change is larger than 5.01±0.7 μGal/a, which is probably caused by the distribution of mass below the earth. The rate of land subsidence of Wuhan area is 3.27±0.65 mm/a determined from combined long-term absolute gravity measurements and GRACE satellite data according to the two system difference.

Validation and Analysis of the Antarctic Digital Elevation Models Based on Airborne Altimetry——A Case Study of Thwaites Glacier, West Antarctica

HUANG Kewei, LI Fei, ZHANG Shengkai, HAO Weifeng, XIAO Feng, YUAN Lexian

2016, 45(5):  544-551.  doi:10.11947/j.AGCS.2016.20150290

Asbtract ( )   HTML   PDF (2056KB) ( )  

References | Related Articles | Metrics

Based on the IceBridge airborne altimetry data collected over Thwaites Glacier, West Antarctica, the accuracy of ICESat satellite altimetry data and four widely used DEMs of Antarctica, i.e., JLB97 DEM,RAMPv2 DEM,ICESat DEM and Bamber 1 km DEM were validated and analyzed. The results show that both of ICESat satellite altimetry data and ICESat DEM feature high reliability, with a bias less than 5 m and a standard deviation less than 15 m. The reliability of Bamber 1 km DEM is a bit lower than that of ICESat satellite altimetry data and ICESat DEM. The standard deviations of JLB97 DEM and RAMPv2 DEM comparing with IceBridge airborne altimetry data are larger than 30 m, and the reliabilities for JLB97 DEM and RAMPv2 DEM are low especially in the sloped areas.

Total Robustified Least Squares Estimation in Partial Errors-in-variables Model

ZHAO Jun, GUI Qingming

2016, 45(5):  552-559.  doi:10.11947/j.AGCS.2016.20150374

Asbtract ( )   HTML   PDF (3583KB) ( )  

References | Related Articles | Metrics

The weighted total least-squares (WTLS) estimate for the partial errors-in-variables (EIV) model is very susceptible to outliers. Because the observations and coefficient matrix in the partial EIV model may be contaminated with outliers simultaneously, a total robustified least squares (TRLS) estimation for the partial EIV model is proposed by combining a two-step iterated algorithm of the WTLS estimate with the equivalent weight method of robust M-estimation. And the uniformly most powerful test statistics are constructed to determine the down-weighting factors. For the characteristics of the two-step iterated method, two different down-weighting schemes are presented. In the first scheme down-weighting is only implemented for the coefficient matrix and not for the observations when some elements of the coefficient matrix are estimated, and the second scheme is contrary. A simulated two-dimensional affine transformation and a linear fitting with real data are analyzed. The results show that the TRLS with the first scheme is superior to one with the second scheme, and it outperforms the existing robust methods with residual and posterior estimate of variance of unit weight and existing robust methods for the general EIV model.

Series Expansion for Direct and Inverse Solutions of Meridian in Terms of Different Latitude Variables

GUO Jiachun, LI Houpu, ZHUANG Yunling, LI Dajun, WU Yanlan

2016, 45(5):  560-565.  doi:10.11947/j.AGCS.2016.20140575

Asbtract ( )   HTML   PDF (998KB) ( )  

References | Related Articles | Metrics

Formulas for direct solutions of meridian written by the reduced and geocentric latitudes respectively were derived by series expansion. Meanwhile, according to Lagrange inversion theorem, formulas for inverse solutions of the issue were also expressed in terms of the same latitudes. These two formulas were structurally consistent with that expressed by geodetic latitude ones. In these sets of formulas, internal connection between meridian and three different types of latitude were realized. Analysis and numerical calculation showed that the direct and inverse meridional solution with reduced latitude was of higher precision than that with geodetic latitude, and furthermore, there had a unified theory between meridian theory and classical geodetic problems expressed by reduced latitude.

Regularization solution of Small Baseline Subset Deformation Model Inversion

JIANG Zhaoying, LIU Guolin, TAO Qiuxiang

2016, 45(5):  566-573.  doi:10.11947/j.AGCS.2016.20150143

Asbtract ( )   HTML   PDF (6510KB) ( )  

References | Related Articles | Metrics

For the coefficient matrix of the normal equation is ill-conditioned during inverting deformation model of small baseline subset (SBAS) InSAR technique, a regularization robust method is proposed. Based on Tikhonov regularization theory, this method converts the problem of how to solve the deformation rate into minimization problem. According to L-curve method to choose regularization parameter, considering the relationship between the individual components of least-squares residuals to choose regularization matrix, thus it achieves robust solution of SBAS deformation model inversion. We adopt respectively least-squares estimation, ridge estimation and Tikhonov regularization method to deal with 29 ENVISAT ASAR dataset relevant to the Beijing area, achieving the subsidence rate map of the study area. Through comparative analysis among the mean square error (MSE) of 21 points on behalf of the different subsidence, temporal coherence values and MSE maps of the entire study area, we confirm that Tikhonov regularization robust method in inverting SBAS deformation model can obtain more reliable results of deformation monitoring.

An Bivariate Filtering Algorithm for Interfere Complex Wavelet Complex Domain

HE Yonghong, ZHU Jianjun, XIE Qinghua, XU Bing, FU Haiqiang

2016, 45(5):  574-580.  doi:10.11947/j.AGCS.2016.20140546

Asbtract ( )   HTML   PDF (11439KB) ( )  

References | Related Articles | Metrics

For complex wavelet bivariate filtering only considering real part, ignoring the imaginary part, it directly leads to the increase of signal phase noise,and influences the effect of filtering, An filtering algorithm based on complex wavelet and complex domain bivariate mode is proposed.Double variable Bayesian estimation algorithm was promoted from real field to complex field, the correlations between real and imaginary part were depicted using noise probability density function, the noise variance and the signal variance were estimated making use of the wavelet decomposition complex coefficient,complex domain double variable filtering model was established, Bayesian estimation of interferogram was obtained. Experimental results show that the algorithm has a stronger inhibitory noise ability, keep the edges and details of interferogram, the filtering performance is better than real domain complex wavelet bivariate filtering, Goldstein filtering, single wavelet filtering and optimal integration filtering methods.

Automatic Cloud Detection for Chinese High Resolution Remote Sensing Satellite Imagery

TAN Kai, ZHANG Yongjun, TONG Xin, KANG Yifei

2016, 45(5):  581-591.  doi:10.11947/j.AGCS.2016.20150500

Asbtract ( )   HTML   PDF (19245KB) ( )  

References | Related Articles | Metrics

Cloud detection is always an arduous problem in satellite imagery processing, especially the thin cloud which has the similar spectral characteristics as ground surfacehas long been the obstacle of the production of imagery product. In this paper, an automatic cloud detection method for Chinese high resolution remote sensing satellite imagery is introduced to overcome this problem.Firstly, the image is transformed from RGB to HIS color space by an improved color transformation model. The basic cloud coverage figure is obtained by using the information of intensity and saturation,followed by getting the modified figure with the information of near-infrared band and hue. Methods of histogram equalization and bilateral filtering, combined with conditioned Otsu thresholding are adopted to generate texture information. Then the cloud seed figureis obtained by using texture information to eliminate the existed errors in the modified figure. Finally, cloud covered areas are accurately extracted by integration of intensity information from the HIS color space and cloud seed figure. Compared to the detection results of other automatic and interactive methods, the overall accuracy of our proposed method achieves nearly 10% improvement, and it is capable of improving the efficiency of cloud detection significantly.

Application of Variance Components Estimation in Airborne InSAR Block Adjustment

XIONG Xin, JIN Guowang, ZHANG Hongmin, XU Qing

2016, 45(5):  592-600.  doi:10.11947/j.AGCS.2016.20150415

Asbtract ( )   HTML   PDF (2414KB) ( )  

References | Related Articles | Metrics

Based on the idea of posterior variance component estimation, aiming at the problem that variance component for each observation component can't be estimated directly, the theory of weights determination for airborne InSAR interferometric parameters calibration with block adjustment is studied and the corresponding calibration method is designed on the basis of the extended model of variance components estimation of Helmert type. Calibration experiments performed on Chinese dual antenna airborne InSAR data confirm that the calibration schemes with posterior variance component estimated can take generation accuracy and mosaic accuracy of DEM into account reasonably.

Laboratory Geometric Calibration of Non-metric Digital Camera

YUAN Feng, ZHANG Jixian, QI Weijun, FANG Aiping

2016, 45(5):  601-607.  doi:10.11947/j.AGCS.2016.20140539

Asbtract ( )   HTML   PDF (1723KB) ( )  

References | Related Articles | Metrics

Geometric calibration of non-metric digital camera, including the accurate determination of interior orientation elements and distortion parameters, directly affects the ultimate accuracy of its using in aerial photogrammetry. In this paper, a laboratory geometric calibration system of non-metric digital camera is developed. A collimator and a star tester are used as the target generator in this system. After measuring locations of targets in CCD and corresponding angles of parallel lights, high precision geometric calibration can be accomplished. Two kinds of mainstream digital aerial cameras, Canon EOS 5D Mark Ⅱ and Hasselblad H3D, are used to take experiments based on this system and the results are analyzed. Experiment results show that the method of this paper is correct and the calibration precision is reliable.

An Optimization Algorithm for Multi-characteristics Road Network Matching

FU Zhongliang, YANG Yuanwei, GAO Xianjun, ZHAO Xingyuan, FAN Liang

2016, 45(5):  608-615.  doi:10.11947/j.AGCS.2016.20150388

Asbtract ( )   HTML   PDF (1300KB) ( )  

References | Related Articles | Metrics

Identifying homonymous road objects is a crucial prerequisite to the integration, updating and fusion of road data. Road networks matching is of great theoretical research value and practical significance in aspect of intelligent transportation system and location-based Service. This paper proposed an optimization algorithm for multi-characteristics road network matching. Designed from shape, distance and semantics aspects, three similarity characteristics-shape differences based on area accumulated, mixed median Hausdorff distance and distance with global weighted attributes, described candidate corresponding pairs more accurately. Then, the matching regression model could be then constructed by training the similarity samples set through SVM algorithm. Finally, the constructed model can be used to predict whether the road matching pairs were matched. A great number of experiments show that the algorithm achieves a robust matching precision and recall even for road networks data with apparent non-rigid deviation. And the proposed method can be effectively applied for road networks matching with multiple matching relationship.

A Bootstrapping Based Approach for Open Geo-entity Relation Extraction

YU Li, LU Feng, LIU Xiliang

2016, 45(5):  616-622.  doi:10.11947/j.AGCS.2016.20150181

Asbtract ( )   HTML   PDF (992KB) ( )  

References | Related Articles | Metrics

Extracting spatial relations and semantic relations between two geo-entities from Web texts, asks robust and effective solutions. This paper puts forward a novel approach: firstly, the characteristics of terms (part-of-speech, position and distance) are analyzed by means of bootstrapping. Secondly, the weight of each term is calculated and the keyword is picked out as the clue of geo-entity relations. Thirdly, the geo-entity pairs and their keywords are organized into structured information. Finally, an experiment is conducted with Baidubaike and Stanford CoreNLP. The study shows that the presented method can automatically explore part of the lexical features and find additional relational terms which neither the domain expert knowledge nor large scale corpora need. Moreover, compared with three classical frequency statistics methods, namely Frequency, TF-IDF and PPMI, the precision and recall are improved about 5% and 23% respectively.

The Standardization Method of Address Information for POIs from Internet Based on Positional Relation

WANG Yong, LIU Jiping, GUO Qingsheng, LUO An

2016, 45(5):  623-630.  doi:10.11947/j.AGCS.2016.20150618

Asbtract ( )   HTML   PDF (1194KB) ( )  

References | Related Articles | Metrics

As points of interest (POI)on the internet, exists widely incomplete addresses and inconsistent literal expressions, a fast standardization processing method of network POIs address information based on spatial constraints was proposed. Based on the model of the extensible address expression, first of all, address information of POI was segmented and extracted. Address elements are updated by means of matching with the address tree layer by layer. Then, by defining four types of positional relations, corresponding set are selected from standard POI library as candidate for enrichment and amendment of non-standard address. At last, the fast standardized processing of POI address information was achieved with the help of backtracking address elements with minimum granularity. Experiments in this paper proved that the standardization processing of an address can be realized by means of this method with higher accuracy in order to build the address database.