Table of Content

22 October 2009, Volume 38 Issue 5

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学术论文

Local Gravity Field Model Based Underwater Gravity Aided Inertial Navigation

WANG Zhi-Gang ¹,Shaofeng Bian²

2009, 38(5):  0-414. 

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In order to inplementing underwater gravity aided inertial navigation on Kalman filter, the modeling of gravity measurements and their errors is requred. Due to that background a new pattern of gavity aided navigation which is based on local gravity field modeling is given in this paper. In this paper, a fast Fourier series based local gravity field modeling is firstly introduced, and by which the difference between measured gravity and indicated gravity is then expressed as continual analytical equation. After that, the extended Kalman filter is introduced, with the gravity difference used as measurement, to optimum estimate the position error of INS. At the end of this paper a simulation is done on gravity anomaly database, and form the results we can see that the mean error of local gravity field modeling is less than 0.1331mGal, and the mean location error in longitude and latitude is 0.1975 and 0.2499 nautical mile respectively.

NORMAL DENSITY OF THE EARTH

HAO Xiao-Guang ¹, ², ², ², ²

2009, 38(5):  0-414. 

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In terms of level spheroid of the earth gravity and Maclaurin-Pizzetti spheroid, according to a series of viewpoints and contents of parameter spheroid, latitudial density, quasi-isopotential condition, approximation level spheroid shown in authors’ recent decade year researches, we propose the concept of earth’s normal density, and solve earth’s normal density distribution for earth’s core spheroid-crust mantle spheroid layer (CS-CMSL) model. On the basis of the concept of earth’ normal density, we advance a new topic of earth gravity research for earth’s normal density hypothesis and slab movement gravity mechanism.

Analysis and Research of Radio occultation Air Detection System’s Interference Suppression Based on GNSS

Zhang Jian-Jun

2009, 38(5):  0-414. 

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The GNSS occultation technology is one of most potential development directions in the current earth's atmosphere survey, and has already successfully applied in domains weather predict, climate diagnostic, global change and so on. But in GNSS radio occultation air detection system, because the GNSS refraction signal’s power is too weak, the GNSS close satellite signal disturb the reception of GNSS refraction signal seriously. This problem causes that the receiver suppressing the GNSS interference signal has been a key question. This article according to the mutual correlation characteristic of GNSS satellite signal, the algorithm of using the subspace projection in interference suppression is put forward, and the improved algorithm is analyzed. The algorithm accuracy was appraised using the SINR and error rate of the system's output signal , also decreases the computation largely.. The analysis of simulation result has confirmed the model validity.

Generation of Approximate Epipolar Lines from Satellite Stereo-Imagery based on Projection Reference Plane

HU Fen ¹, ², ²,²,², ²

2009, 38(5):  0-414. 

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It is almost impossible for the linear pushbroom satellite images to define the rigorous epipolar geometry, as the accurate geometric relation between the object-space and image-space is difficult to fully determine due to the multi-center projection imaging mode adopted. Therefore, study on epipolarity model of satellite stereo-imagery will be theoretically and practically significant in application field of modern photogrammetry. Although various models have been studied and used to generate epipolar images of satellite stereo pairs, some technical limitations still exist when taking the universality, applicability and implemental simplicity into account. Accordingly, this paper proposes a novel epipolarity model for satellite stereo-imagery based on the Projection Reference Plane (PRP) of object-space. Firstly, the principle of the PRP-based epipolarity model is described; and then, the workflow of the PRP-based epipolar resampling is outlined in detail; finally, the epipolar images of SPOT5-HRG stereo-imagery, IKONOS stereo-imagery, IRS-P5 stereo-imagery and Quickbird stereo-imagery are respectively generated to prove the feasibility, correctness and universality of the new method, and it is demonstrated that the vertical parallaxes of all the extracted conjugate points have reached the subpixel level on the generated epipolar image pairs. As the rigorous corresponding relationship between the original image point and the epipolar image point can be simply derived from the provided image orientation data, the method is quite practical for application; besides, by rearranging the approximate epipolar lines on the defined PRP, the stereoscopic model which is horizontal to the object-space and with consistent resolution is thus available.

The Methods of Removing Attitude errors for Multibeam Bathymetry Data

2009, 38(5):  0-414. 

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In this paper, we analyzed the instantaneous errors of attitude in multibeam survey in detail. According to different sources, we use corresponding algorithms to correct induced depth errors. At first, we need to remove the influence of terrain trend. Then the linear relation of depth errors and roll rate or roll can be used to infer whether the errors are induced by time delay or attitude scale. Once the sources of attitude are known, the parameters of biases can be obtained by adjusting until disappearance of the linear relations. Finally, the induced depth errors will be corrected by the parameters. The method is verified by the real data. It can provide a reference for improving multibeam bathymetry, especially in shallow water.

Observation Design for Determining Regional Gravimetric Geoid (Quasi-geoid)

XU Xi ¹,Jianjun Zhu ²,²

2009, 38(5):  0-414. 

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Relative accuracy of regional gravimetric geoid (quasi-geoid) determination is estimated by an analytical method, which is determined by regional terrestrial gravity measurements and geopotential model. First, the accuracy relationship between terrestrial gravity measurements and spherical harmonic coefficients is deduced based on the Stokes formula. Second, based on the truncated approach of “remove-restore” and spherical harmonic expansion of the covariance function, the analytical relationships among errors of inner terrestrial gravity measurements, errors of outer geopotential model and relative accuracy of regional gravimetric geoid are deduced respectively. Thirdly, for convenience of calculation, it is proposed that frequency truncation errors of inner terrestrial gravity measurements and outer geopotential model be merged and then reclassified in two parts: ① at frequencies higher than inner gravity data in global area, ② at frequencies between inner gravity data and geopotential model in outer area. They are estimated respectively by using empirical degree-variances model. Simulation indicates the corresponding relationships among terrestrial gravity measurements accuracy, resolution and integral radius, geopotential model accuracy and resolution and the relative accuracy of regional gravimetric geoid (quasi-geoid) determination.

Improving of Cycle Slip Detection and Correction by Using the Combination of GPS Observations

ZHANG Cheng-Jun

2009, 38(5):  0-414. 

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It must use the precise P-code for detecting and repairing cycle slip by using classical method with pseudo range and carrier phase combination observations, so its application area is limited. It is improved by considering the combinations for calculate ionosphere effect remains, the improved formulas are derived, the conditions of combinations which can detect and repair cycle slip are also given. Two experiments are made to test the effect by using L1,-1、L-3,4、L-7,9 and L－14，18 combinations. Results show that the improved method can detect and correct all cycle slips when using static observations and almost whole cycle slips when using kinematic observations. Key words: GPS; combination observations; cycle slip; detecting and correcting

Research on Equality Constraint Inversion with Ill-posed Constraint Matrix

¹,Caijun XU², ²

2009, 38(5):  0-414. 

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Prior information and many kinds of observations are often used in equality constraint inversion. In this thesis, solving method to equality constraint inversion is discussed, the concept and evaluate method of Ill-posed character of constraint matrix are given. The influence to adjustment results from constraint matrix Ill-posed character is deduced. Through an example, the influence to inversion result from constraint matrix Ill-posed character is analized. The SVD method is used to solve Ill-posed problem of constraint matrix. The problem that inversion result is not stable because of constraint matrix Ill-posed character is solved effectively. At last, throught some programmes of inversion, the methods are analized, and some conclusions are obtained.

Automatic Road Extraction from High-Resolution Remote Sensing Image Based on Feature Fusion

2009, 38(5):  0-414. 

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Road extraction from high-resolution remote sensing image is considered as an important and difficulty task. Remote sensing image including complex information, the methods that extract roads by spectral, texture and Linear features have limit. Also, many methods need human-intervention to get the road seeds (semi-automatic extraction). So, they have the great human-dependence and low efficiency. The automatic road-extraction method, which uses the image segmentation based on principle of local gray consistency and integration shape features, is proposed in this paper. Firstly, the image is classified by segmentation and using several shape features, then obtain linear and curve road, so rectified some method’s defect that just only extract linear roads. Secondly, the second step of road extraction is carried out on the region growth, so the road seeds are automatic selected and the road network is automatic extracted. Finally, the extracted roads are regulated by combining the edge information. In experiments, the good symmetrical road surface image and the bad symmetrical road surface were chosen for experiments, and the result proved that the method of this paper is promising.

Investigation on Algorithm of Inversing Ocean Surface Current with a sequence of X-Band Radar Images

2009, 38(5):  0-469. 

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The ocean surface current (OSC) is one of the key factors which affect accuracy in OSC parameters inversed with a sequence of X-band radar images. Although OSC cannot be directly measured by instruments, this paper investigates the OSC inversion algorithm. In the process of OSC inversion, the energy cost function with constraint terms is established, thus resulting in OSC inversion formulae. The optimum solution can be derived by weighted least squares method. The inversion accuracy can be improved by taking into account the high-order dispersion relationship. In order to test the inversion algorithm, a sequence of radar images are acquired by X-band radar, both moving average and dispersion relationship are used to filter noises in the images. The algorithm is finally validated with the real X-band radar images, and the preliminary testing results show that the inversion approach is feasible.

Computational Model and Its Precision Evaluation for Time Comparison by Two-way Satellite Common-view

2009, 38(5):  0-469. 

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Time synchronization is one of the pivotal technologies in the design of satellite navigation and positioning system. According to the principle of time comparison by two-way satellite common-view, its computational model in the earth-centered inertial reference frame with the second order of the velocity and the first order of acceleration of satellite and ground-station is particularly deduced. Taking the GEO and GPS satellites as examples, the magnitudes of the influences of every item in the distance correction time delay of the computational model to the relative clock difference between ground stations are analyzed. And the results show that when having time comparison between the GEO or GPS satellite and the ground station, the velocity of satellite and ground station should be taken into account in 1ns computational precision; and the second order of the satellite velocity, the satellite acceleration, the effect of relative clock difference between ground station and satellite on the satellite velocity, the effect of relative clock difference between ground stations on the ground station velocity should also be taken into account in 1ps computational precision.

Outlier Snooping Based on the Test Statistic of Moving Windows and Its Applications in GOCE Data Preprocessing

¹, ²

2009, 38(5):  0-414. 

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After a brief review of the methods of detecting, identifying and controlling outliers, a new outlier snooping method is developed for the time series of satellite gravity data based on least square collocation. The main idea is to predict observable of the possible outlying point from neighboring data and to compare the prediction error with its estimated variance, and then perform outlier snooping according to a certain test statistic and a given significance level. Based on the above idea, the test statistic of t-distribution is constructed and a new statistical test of moving window is proposed. A simple correlation function, the determination of window width and a detail iteration testing procedure are presented. A numerical example from the simulated Tzz of GOCE satellite is performed. The results show that the new testing method can efficiently detect and identify the outliers.

博士论文摘要

3D Line Segment Extraction and Object Recognition based on Ground Mobile Mapping Sequential Stereo Imagery Data

2009, 38(5):  0-414. 

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学术论文

A New Adaptive INSAR Interferogram Filter Based on SNR

2009, 38(5):  0-414. 

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This paper proposed a Signal-to-Noise (SNR)-based filtering algorithm for reducing interferometric phase noises. The algorithm is a modification to the Goldstein radar interferogram filter. It makes the Goldstein’s filter parameter dependent on local SNR of interferogram. This modification can make the areas with low SNR strongly filtered, while those with high SNR weakly filtered. Experiment results with simulated and real data demonstrate that the new filter can effectively reduce phase noises in InSAR interferogram.