Xiang Maosheng

Introduction on an experimental airborne InSAR system

This paper gives a technical description of the system hardware, data processing flow as well as experimental results of the Experimental Airborne InSAR System, developed by Institute of Electronics, Chinese Academy of Sciences and sponsored by the Information Technology Committee of Chinese High-Tech Program. The system operates in X-band range and is configured as a dual-antennae cross-track interferometric SAR with the main parameters: 9.6GHz operating frequency, 100 MHz bandwidth, 0.60 m baseline, up to 10 km swath width, 2m×2m ground resolution, excelled 5m height accuracy, and two polarized types.

SAR raw signal simulation based on GPU parallel computation

In this paper we present a raw signal simulator based on GPU parallel computation for synthetic aperture radar. We describe a mathematical model of SAR simulation based on FFT in detail and implement it through GPU parallel computation. GPU has a better performance in complex calculation than CPU. It supports parallel computation and raises the speed of algorithms. At the last part of this paper, a simulation comparison is given. The result shows that the simulator base on GPU parallel computation improves the efficiency of algorithm. It is very useful when the algorithm consumes large amount of CPU time.

The study of rough-location of remote sensing image with coastlines

In this paper, we introduce a new method to locate the remote images. By using the Geographic Information System(GIS) resources, we can extract the coastlines information. At the same time, by using image processing technologies, we can also extract the similar information from remote images. Based on the image matching technologies, we can roughly locate the remote images. Some simulation experiments are implemented on remote sensing images with coastlines. Preliminary results verify the feasibility of the technique.

SAR raw singal simulation accounting for antenna attitude variations

An efficient SAR raw signal simulator accounting for antenna attitude variations is presented here, based on the 2-demensional Fourier domain formulation of SAR raw signal in presence of antenna beam pointing errors. It can meet the requirements of InSAR system simulation to deal with the extended scenes. The validity limit is analyzed to show that this algorithm is suit for the simulation of practical systems.

Geo-referencing airborne interferometric SAR data

Synthetic aperture radar (SAR) plays an important role in the earth observation system owing to its all-weather capability. Having the ability of getting the altitude of ground and image simultaneously, interferometric SAR (InSAR) technology becomes used in many fields in recent years. Airborne InSAR system is also developed successfully in June 2004 in China and now many flight tests have been conducted. We can get the SAR backscatter energy and altitude of ground i.e. SAR image and DEM through unwrapping the phase. But the reference coordinates of DEM and SAR image are imaging geometry coordinates which use range number and azimuth number as reference. The imaging geometry coordinates must be changed into geographic coordinates if DEM and SAR image are used in practice, this procedure is called geo-referencing. Owing to its side looking property, the undulation of ground height influences SAR image severely, nevertheless the altitude of ground which is very useful to eliminate the influence of ground undulation can be generated through InSAR. It is very difficult to get the precise position and velocity of airplane in the past, but now we can get precisely position, velocity and attitude using GPS/INS integrated system with the development of inertial navigation system (INS) and the mature of GPS, especially differential carrier phase GPS. The position and orientation system(POS) of Applanix company can provide high accurate position, velocity and attitude, and its position accuracy can reach 0.05~0.30m and velocity 0.0005m/s by post processing using GPS and INS combined filter algorithm We apply Doppler and range equations to geo-reference the DEM and image of InSAR based on the position and velocity of platform which is determined by POS/AV system. The principle and accuracy of geo-referencing InSAR data are discussed in the paper and the test data are processed using this method. Error estimation and field accuracy checking are also presented and the result is satisfactory.

The method of InSAR/INS integrated navigation

This paper presents the concept and method of InSAR aided INS navigation. InSAR interferometric phase is sensitive to the attitude of the platform and the terrain height, so it can be used to improve the precision of navigation substantially. InSAR/INS integrated navigation system can be used on the flight vehicle navigation and it can satisfy complicated topography and long-distance accurate autonomous navigation. The technical route of InSAR/INS integrated navigation system is discussed in detail in this article. We can obtain the location shift of azimuth and range by matching two interference fringes, one is produced by InSAR system and another is generated by reference path and digital elevation database. And the simulation results indicate the precise and efficient of the matching algorithm. With the aid of the location shift we can inverse the attitude and position information of the platform. The location shift and the IMU information are set to the all-state combined filter to obtain the navigation output.

Simulation of interferograms for multi-baseline InSAR study

It can improve both accuracy and reliability of derived DEMs by combining multi-baseline InSAR data, more accurate height information can be derived from InSAR data with longer baseline and less difficulty can be met with shorter baseline. In order to study technique of multi-baseline InSAR, a simulation algorithm for interferograms of multi-baseline InSAR was proposed. It was based on boresight imaging model, and so F.Leberl formula was applied to establish relations between pixels and ground points. The interferometric phases were calculated with different baselines by iterative method. The DEM derived from SIR-C/X-SAR data was used in experiment, and interferograms with different baselines were simulated successfully.

An improved wavenumber domain algorithm for circular SAR and cylindrical reconstruction areas

In this paper, an improved wavenumber domain imaging algorithm is proposed for circular synthetic aperture (CSAR) data taken in stripmap mode. The proposed algorithm allows to reconstruct an image on a cylindrical surface. The range trajectory is approximated with the fourth-order terms expansion and the echo signal is transformed to the wavenumber domain by using a principle of stationary phase. Based on the spectrum, the interpolation of the algorithm is deduced, and the residual phase is compensated. The valid aperture length of the proposed algorithm is greatly increased, comparing with the algorithm based on range expanded to quadratic terms. The simulation results validate the high-performance of the improved wavenumber domain imaging algorithm.