2006 Vol. 31, No. 11
The photographic principle of SPOT 5 HRS is discussed in detail.By a series of coordinate system transforming,the rigorous orbit model of direct geo-referencing without ground control point is established.Experimental results of three datasets show that there are systematic errors existed.Once a ground control point is introduced,the result is improved tremendously.Results of 580 km test dataset with one ground control point are still better than 20 m for the planar position and about 10m for the altitude.It shows that the orbit itself is very stable.The HRS imagery has promising potential for various applications.
The concept of connective degree is utilized for the identification of topological difference in the geometric structure of a line,its generally topological definition of a line is given.A generic model,called the 4-intersection-and-difference,is set up for the description of basic line-line topological relations,upon which a conceptual neighborhood graph is built with the consideration of topological distance.It concludes that the proposed model in this paper can represent the property of topological changes,and basic relations between line segments in IR~1 and IR~2.
A new adaptive regularized super-resolution reconstruction method for digital image sequence is introduced.In this method,the super-resolution problem is approached from a MAP estimation framework,and a technique to determine the regularization parameter adaptively is presented.The proposed method is tested on simulated image sequence and real image sequence.Experiment results indicate that this method is better than the conventional reconstruction methods on both visual judgment and objective statistical analysis.
Firstly,the methods used to estimate the aboveground biomass of submerged vegetation are briefly reviewed.Secondly,on the bassis of the reviewing,the process using Landsat 5 TM imagery to estimate aboveground biomass of submerged vegetation in Jiangxi Poyang Lake National Nature Reserve is discussed in detail.The results showed that it was infeasible to estimate the aboveground biomass using Landsat 5 TM imagery combined with traditional field sampling method and computation technologies in this particular study area.Finally,the reasons causing this infeasibility were analyzed,and suggestions for future research were presented.
This research was carried out with two phases of remotely sensed images covering Nanjing City in 1988 and 1998 respectively to monitor the land use change.At first,two images were normalized at the same radioactive level of 1988's TM image,registered with high geometric accuracy less than 0.5 pixel errors and purified training regions,after pretreatment of TM data.Then maximum likelihood classification is applied for both images.Finally the GRID model of Arc/Info software is used to algebraically calculate two classified maps with AML codes and obtained information of land use change.Through analyzing the result indicates that in the past period of ten years arable land decreased largely was mainly due to urban extension,and forest increased was due to some protective policies and activities of forestation.
A new algorithm of spatial data partitioning is presented based on Hilbert curve which is one of the space filling curves.The new spatial data partitioning HCSDP algorithm gives a new vector data partitioning policy on the parallel spatial database system.Taking the characteristic of the variant-length of vector data records into account,HCSDP algorithm divides uniformly the huge volume of spatial data set into multiple parts and putting them onto the different processing nodes for avoiding the data skew.The advantages of HCSDP comparing are discassed with the algorithm used in Oracle spatial,and the validity and the efficiency of the algorithm are illustrated by the experimental results.
On the basis of on the analysis of current spherical spatial data structure,the clew of the spherical spatial basal subdivision mode which uses Snyder equal area projection on the truncated icosahedron DGG is discussed,and then global multi-resolution overlay is obtained by subdividing hierarchically on the initial projection plane according to the hexagonal grid.The essential clew of managing the three leaves nodes and tiles code is put forward based on hexagonal grid,and the hexagonal grid expression modes of different spherical entities are established.And on the basis of these clews,the algorithm of generating the voronoi diagram based on the spherical hexagonal overlay is put forward and the exactness and efficiency of the algorithm are verified through experiments.
A fusion method is introduced which is based on morphological pyramid decomposition,and applied to ikonos images.As a non-linear filter,the morphological filter outperforms the linear filter(eg.Gaussian filter) in precise edge localization,and better represents the detailed spatial information of images.Results and analysis of the experiments show that the fusion method based on morphological pyramid is better than the methods steming from Laplacian pyramid or contrast pyramid.
The spectral curves between 400 nm~2 500 nm of 174 soil samples which were collected in Hengshan County and Yixing County were studied.Fourteen types of transformation were applied to the soil reflectance R to remove the noise and linearize the correlation between reflectance(independent variable) and soil physical-chemical properties(dependent variable).Then,methods such as derivative spectrum technology,stepwise regression analysis,were applied to study the relationship between these soil spectral features and soil organic matter content.It shows that order 1derivative of the logarithm of albedo is the most sensitive to SOM among the various albedo transforms in consideration.The regression model whose coefficient of determination reaches 0.885 is built.
Two kinds of fading filters and their principles are introduced.An adaptive robust filter is given with corresponding principle.The basic abilities of the fading filters and adaptively robust filter in controlling the influences of the kinematic model errors are analyzed.A practical example is given.The results of the fading filter and adaptively robust filter are compared and analyzed.
In order to improve the shortcoming of the traditional multibeam data processing,a new method,which blends GPS height and heave to present the actual height at transducer,is studied.In the fusion,GPS height and heave need to be corrected to transducer by attitude correction firstly.Secondly,GPS height needs to be checked and modified by heave check and modification itself.In addition,filter methods are studied by comparing Buttworth filter and FFT spectrum analysis,the latter is chosen finally for extracting height-frequency signal from heave and low-frequency signal from GPS height,and blending a new height at transducer.The applications of the method in few experiments prove that it has higher accuracy relative to the traditional.
The principle and method of solving three types of satellite gravity gradient boundary value problems by least-square are discussed in detail.And the kernel function expressions of least square solution of three geodetic boundary value problems with the observations are presented.From the results of recovery of gravity field using simulated gradient tensor data,a conclusion can be drawn that the satellite gravity gradient integral formula gotten from least square,used for recovering the gravity field,is valid and rigorous.
The propagating geometry and the waveform of the GPS reflected signals were expatiated in detail.Furthermore,the principle and the method of retrieving ocean surface wind were presented.In order to test the feasibility of retrieving,the experiment data obtained by NASA in hurricane Michael was used.The result shows that the estimated retrieval accuracy of wind speed is about 2 m/s.
In order to derive a relatively noise-free time series from the GPS results,an integrated method based on adaptive noise cancelling principles and wavelet de-noise method is presented.To verify the effectiveness of the method,an experiment is carried out,the results indicate that the adaptive noise canceller is a powerful signal decomposer,which can significantly mitigate multipath effects since multipath tends to exhibit the same pattern between consecutive days;wavelet filter is a suitable tool to separate stochastic noise that cannot be filtered by ANC method form signal.This kind of combination is superior to single filtering method.
The determination of the optimum draggle distance between the sensor and the surveying boat is an important task in marine magnetic survey.It will greatly influence the surveying precision and working efficient.The surveying boat was seemed as a magnetic dipole in this paper,and the magnetization model of the boat and the formula that calculate the magnetic field strength behind it was deduced.The theoretical method which determine the optimum draggle distance was given out.The applicability of the method was validated with the practical test.
An algorithm is presented for the improvement of harmonic tidal analysis along T/P tracks,in which the differences between the observed sea surface heights at adjacent points are taken as observations,and the observation equations are constrained with the results of the cross over analysis.It is indicated that the algorithm presented can efficiently remove non-tidal effects in the altimeter observations,and improve the precision of tide parameters.Moreover,parameters along altimetry tracks represent smoother distribution than those obtained from traditional algorithms.
The principle of VRS technology is discussed with corresponding formula deduction,and descriptions of VRS corrections and virtual observations generation and positioning algorithm are presented in detail as well as their applications.
The characteristics of the normal equation created in recovering the earth gravity model(EGM) by least-squares(LS) adjustment from the in-situ disturbing potential has been discussed in detail.It can be concluded that the normal equation of this type of problems depends only on the orbit.Based on this characteristic,whether a reference field is used or not has no effects on the LS solution is explained.Staring from this point,four sets of disturbing potential on the orbit with different level of noise have been simulated and used to recover the EGM.The results show that on the current accuracy level of the accelerometer calibration,the accuracy of the EGM by LS is not sufficient to reflect the time variability of the EGM as the dynamical method has revealed.
A method combining spatial cluster with data statistical analysis was employed to optimize a land subsidence monitoring network consisted of 86 monitoring points at Tanggu in Tianjin.So the optimized network met with the goal of both maximizing spatial accuracy and minimizing temporal redundancy.Giving the number of monitoring points,an optimized network containing a selection of about 25% monitoring points from the original network was built.
The paper extends the meaning of ecological capacity, considers more comprehensively in multiple ecological functions of ecologically productive land. In this method, the supplier of ecological capacity includes more kinds of resource, such as renewable resource, recyclable waste etc. Therefore, the calculation basis of ecological capacity and ecological footprint becomes more harmonious. As an example, the calculation result of Xiangfan City's ecological capacity in 2001 showed that resource yield method is more reasonable.
On the basis of the theory of ecological footprint, China's ecological footprint in main years from 1978 to 2004 is analyzed.Depending on the long-term data,the curve of the general demand and supply of ecological footprint is depicted,and the trend of the long-term ecological footprint is observed to judge whether it was in equilibrium.The result is that ecological deficit has been increasing in the long-term.And in the end the ecological consistency of China is analyzed using econometric model.
On the basis of the characteristics of the LEO channel,a pilots-aided frequency offset estimation algorithm for OFDM systems is proposed.The simulation results are presented in error probability for integer frequency offset estimation and in mean square error(MSE)for fructional frequency offset estimation.They show that the proposed algorithms are available for frequency offset correction of OFDM systems on LEO satellite channel.
The near stalk interference of the space laser can produce Newton's ring whose centre is very marked.The extremely high accuracy aexamination of linearity can be based on the laser interference Newton's ring.This Newton's ring can be applied in many engineering such as the dam transforms the examination,the examination of the orbit straight line.A method checking the laser Newton's centre by video is introduced.The result of the trials shows that fast Hough transform can produce a good result.