This paper presents a new algorithm to generate the interferometry fringe with high quality in real\|time.It utilizes the techniques of down-sampling and interferometry multi-look processing,the look-up table with linear interpolation,the ECS auto\|registration imaging algorithm with non\|linear approximation,the real\|time interferometry motion compensation,and the improved fast algorithm of computing coherence and filtering the interferometry fringe.The feasibility of generating the interferometry fringe in real\|time with hardware is analyzed and the structure of hardware is given to realize the algorithm too.In the end,the interferometry fringe and coherence map are generated by the algorithm for the airborne X-band InSAR data of Institute of Electronics,Chinese Academy of Sciences,and the results prove the validity of the algorithm.
Satellite-based passive microwave remote sensing data has wide applications in global environmental change research because of the characteristics of all-day observation,penetrability and uninfluenced by clouds.The main drawback of passive microwave remote sensing is the extreme low spatial resolution,which limits the precision of surface parameters retrieval.Due to the restriction of size and weight from satellite payload,satellite passive microwave radiometer can not assemble a large antenna,which causes low spatial resolution.The spatial resolution improvement methods of passive microwave remote sensing data are introduced in the paper.The super spatial resolution method and passive microwave unmixing method based on image processing technology are mainly discussed.The research prospects of the unmixing methods are proposed after the introduction and evaluation of present methods.The effective improvement of spatial resolution of passive microwave data can be used to service for more research and application fields well.The research results provide important information for passive microwave unmixing method with higher precision and more application field.
Passive remote-sensing technology requests high performance of complex correlator.An analog complex correlator has been introduced in this paper,The advantages of this correlator are low power consumption (compared to a digital correlator),small chip area and high sensitivity.Core components of the analog complex correlator are multiplier unit and wideband phase shifter,their manufacture and performance have been discussed and the results have been presented.We have tested the broadband phase characteristic of the correlator and simulated broadband phase\|inversion process.The result of phase inversion accuracy has been given.
Retrieval of cloud top height with oxygen A-band has been proposed for decades.However,with the development of space-based instrument,more attentions are being paid to this field again.Among various retrieval methods,SACURA and FRESCO+ are successful and mature.The ESA had already developed the cloud top height products retrieval by them.In order to evaluate the precision as well as applicability of these products and develop new generation oxygen A-band retrieval method in the future,sensitivity analysis is carried out herein.It is investigated that the result of FRESCO+ is insensitive to the surface albedo,cloud amount and other parameters.The cloud top height is underestimated about 20～750 m.While the result of SACURA is more susceptible to the solar zenith angle,cloud optical depth,surface property and cloud amount.The retrieval results of cloud top height change dramatically.Except the situation that the cloud optical depth is lower than 5,the average error of SACURA is smaller than 300 m with full cloud covering.Meanwhile,the result will be the worst if the value of cloud optical depth is smaller than 5 and the earth's surface is bright.The maximum error is more than 10 km.To confirm the conclusions above,verification with experimental results are also carried on.We firstly analyse statistically the satellite's cloud top height L2 products of 2008 which covers China and neighboring regions,and then compare with MACR and BBSS's information supplied by the ARM mobile facility located in Shouxian.The analysis shows that the conclusions,which are obtained by the simulations,are accurate and reliable.Besides,some suggestions for improvement of the algorithm and applicability of satellite products are also put forward.
Mixed pixels commonly exist in remote sensing images.They may cause difficulties to process and analyze the remote sensing images.Sub-pixel mapping method is used to solve the problem of mixed pixels.It can obtain more accurate results for image classification and more details of distribution of land cover classes.There are always three steps to preform the sub-pixel mapping:① unmixing the mixed pixel; ② obtaining the soft information;③ mapping at sub-pixel scale.This paper described the details about the sub-pixel mapping method in recent years and reviewed the development of these sub-pixel mapping methods.These methods can be classified into four types:① Spatial correlation-based sub-pixel mapping;② spatial construct information-based sub-pixel mapping;③ article neural network -based sub-pixel mapping;④ pixel swapping-based sub-pixel mapping.Then these methods are contrasted and analyzed as well.Finally,a trend for development of sub-pixel mapping is given in the conclusion
The Defense Meteorological Satellite System(DMSP) Operational Linescan System (OLS) has a unique low\|light imaging capability developed for the detection of clouds lit by mooolight.In addition to moonlit clouds,the OLS sensor also detects nocturnal lights from the earth surface.Hence,DMSP/OLS night\|time emissions data becomes well known as a means of monitoring human activities.In this paper,we reviewed a number of applications that had been developed or proposed based on the DMSP/OLS night\|time emissions data,such as monitoring city lights,light pollution,fires,fishing boats and gas flare,and estimating socioeconomic data.Finally,the advantages and disadvantages of night light data were listed and more applications are expected in the future based on the available light emission data.
raditional research methods in modern glacier changes mainly based on field observations and empirical formula to calculate changes in glacier area,volume and surface velocity,however,since 1980s,with the new technologies of aerial remote sensing images,digital elevation model,radar,etc.developed,the studies of nature and characteristic of glaciers and detection of dynamic changes in glacier have not only become the important trends of glacier research by means of remote sensing method,but also greatly resolved the problems such as limited information in high mountain areas.The computer\|based automatic interpretation methods in the study of glacier area change including threshold and NDSI (Normalized Difference Snow Index),supervised classification and non\|supervised classification,threshold value of band ratio,etc.Although the operating of threshold and NDSI are simple,they are difficult to select the suitable threshold on such issues; Non\|supervised classification method is simple but more constraints.With the accurate selection of training area,the result of supervised classification method is more accurate.The threshold value of band ratio method is the most widely used computer automatic classification because of its simple operation and accurate result.The application of Digital Elevation Model and radar data in the study of glacier volume change preferably improves the accuracy and applicability of traditional methods.And that radar data will not be affected by atmospheric propagation and climate change compensated for the weak script of remote sensing images data which is easily influenced by snow and clouds.With the development and application of high precipitation GPS and radar data,it plays an irreplaceable role in surface velocity studies.
The radar altimeter prelauch calibration was commonly carried our by return signal simulator,so the bias on return signal simulator need to be quantitatively analyzed.The return signal simulator principle,biases such as quadratic phase bias,amplitude and phase bias,delay bias were detailed.In the last section the whole system bias on return signal simulator was calculated.The HY\|2 radar altimeter prelaunch calibration was successfully realized on the basis of return signal simulator precision.
Taking topographic map in 1970s as reference,four periods terrestrial coastlines in Zhejiang province were depicted by using TM data in 1986 and 1995,ASTER data in 2005 and HJ data in 2009.In those four years,changed coastline,increased land area and fractal dimension value were calculated.The conclusions were as follows: ① The three satellite data could meet the precise and quick requirements of rapid coastline change monitoring;② Zhejiang terrestrial coastline fast expanded forward ocean,205.24 km2 newly increased land from 1986 to 1995,319.85 km2 from 1995 to 2005,484.75 km2 from 2005 to 2009;③ The fractal dimension of coastline in Zhejiang province was relative small,which meant low level of complex,the value of fractal dimension was gradually decreased in recent two decades.
Hill\|slope terrain has an essential influence on microwave radiation due to slope angles and aspects.It is necessary to experiment in the field by observed different topographic landscapes we designed based on the trunk\|mounted microwave radiometer.In the configuration of AMSR\|E,the observed data compared with simulations of relief effects modeled by AIEM and Fresnel equation.The result shows there are 10~15K bias of brightness temperatures affected by tilted angles between flat terrain and mountainous terrain.When frequencies less than 10 GHz,the relief effect of terrain elevation becomes weakened.And we certified that microwave polarization path and direction changed for surface geometrical property,such as shape and the orientation of hills.
Phenological records provide an integrative indication of the sensitivity of natural systems to climate changes.A smoothing algorithm based on fourier function was firstly applied to the MODIS NDVI dataset to minimize the effects of anomalous values caused by atmospheric haze and cloud contamination,and daily NDVI data were generated.Together with the field observation data,the cropping system and its related phenology in Sanjiang Plain were then estimated based on the smoothed NVDI time-series dataset.The starting dates and the ending dates of growth season were extracted,and were compared to observation data.The results indicate:the starting dates of growing season in Sanjiang Plain focus on 120th\|130th day,and the ending dates of growing season focus on 250th -260th day.The starting and ending dates in 2003 were earlier,while the starting dates in 2005 were delayed.And the starting dates in 2007 were earlier than 2005s,the ending dates in 2007 were the latest.The grow season in 2007 were the longest in the three years.Monitoring spatial patterns of cropland phenology based on MODIS NDVI data is practicable,especially in the large area of crop land.
Using 1990,2009 TM and 2000 ETM remote sensing images,the land use information of oasis plantation and its changing catachrestic were analyzed by ERDAS and GIS,and the landscape pattern and landscape index were analyzed by FRAGSTATS,the results showed that: the study area mainly composed of desert and gobi desert which about 70% of the total area.In recent two decades,Land use style changed greatly,the area of farmland and water reduced.The main reason of Severe degradation of vegetation is changes in precipitation patterns by global climate changing,changes of oasis plantation management and development policy.In recent two decades,landscape isolation and landscape fragmentation show downward trend,and,landscape path shape diversified,it's not conducive to management.The construction of water facilities,such as canals,provide guarantee for the plantation development,but it increased water consumption and went against with ecosystem stability.The oasis plantation has ecological benefits,such as sand fixation,soil improvement,water conservation,biodiversity maintenance and social & economic benefits.
Image segmentation determines the accuracy of subsequent classification in remote sensing.In consideration of the research lacking of evaluation about segmentation technology and limitation of the mainly subjective method currently,quantitative method is used to select optimal segmentation scale in this paper.With object\|oriented segmentation algorithm of Definiens software,standard deviation of all pixels from an image object is used as the homogeneity measured criteria in object,absolute value of mean difference to neighbors is served as the variable of heterogeneity between objects,weighting coefficient of the object area is also considered.With the three evaluation criteria,thinking of multispectral images,the average segmentation evaluation index is constructed.Based on the evaluation index,with goodness test method,QucikBird multispectral image is used to be researched,and the optimal segmentation scales of different surface features are concluded.At last,the average object fit index is used to verify evaluation results,and the feasibility of the evaluation method is discussed.
Review the theories of SST retrieval based on Thermal Infrared remote sensing images and gives the definitions of Skin and Bulk temperature,as well,summarizes the basic algorithms of SST retrieval,including Single Channel Algorithm,Split\|window Algorithm and Multi\|angle Algorithm,especially,focus on the SST Retrieval Algorithms of Landsat TM/ETM+,CBERS-02 IRMSS,ASTER,HJ-1B IRS in detail,which have high resolution TIR channel,finally,comparing characters of various TIR channel aboard and analyses the effective factors of SST retrieval,listing the problems at present and prospecting the research of future.
Thick cloud in remote sensing image greatly reduce the utilization of the images.Using the ability of support vector machine to capture the edge points and image fusion scheme,in this paper,the algorithm based on support vector machine is presented to remove thick clouds in remote sensing image.First of all,support vector value contourlet transform is constructed and the images are decomposed.Then cloud detection and image fusion are carried out.Finally the reconstructed images are got by support vector value contourlet inverse transform.The experimental results reveal that the algorithm can achieve satisfactory result for the remote sensing images with the thick clouds but no overlapping in cloud.Not only the edge information of image is preserved but also the problem of residual clouds is resolved effectively.
Due to the strengths and weaknesses of the existing filtering methods,an improved plane fitting algorithm is presented for filtering of airborne LiDAR data.Firstly,resampled LiDAR data were segmented using region growing method,and then the largest connected region was selected as the initial ground area.Secondly,non\|ground points in the initial ground area were removed by a slope threshold.Finally,the ground points were interpolated using Kriging method and the filtering results were gained.The dataset provided by International Society for Photogrammetry and Remote Sensing (ISPRS) were selected as the test data.The influences of different slope thresholds on the filtering results were given after filtering experiments.The result shows that the optimal filtering effect is the best when the slope threshold sets to 0.5.The overall error rate can be only 4.29%.Contrast to the traditional filtering method based on plane fitting,the proposed method is more simple and practical.
There are many disadvantages in traditional WebGIS development based on data,like difficulties in sharing,high cost for updating and maintenance,etc.At the same time,the increasing use of RIA on the web provides a new avenue of WebGIS development which can solve those problems.In this paper,a RIA WebGIS prototype system is developed based on Adobe Companys Flex Builder software and ESRI Company's ArcGIS REST services.The results indicate that the application of RIA in the field of GIS will lower the degree of difficulty,boost up the users experiences,the combination of Flex and REST is a good choice for WebGIS system development.
