一种在长时间序列SAR影像上提取稳定目标点的多级探测法

基于长时间序列上的差分雷达地表形变检测技术是近年来形变监测领域中一项重要的关键技术,而在长时间序列上稳定目标点的准确提取则是其中的一项重要环节,在此本文提出了一个有效的提取稳定目标点的多级探测方法.该方法以传统的振幅探测法为基础提取稳定目标点,同时针对振幅探测中稳定目标点的分布密度低、不均匀等问题,建立时间相干性计算模型,并利用目标点时间相干信息提取更多满足要求的稳定点目标.本文选用上海地区的26幅ERS-1/2 C波段SAR图像(1992-2000年获取)进行了目标点的提取实验,证实了该方法的有效性和可靠性.

A Multi-Step Detection Method for Extraction of Stable Pointwise Target in Long Temporal SAR Image Series

Spaceborne differential interferometric SyntheticApertureRadar technology (D-InSAR) in long temporal series is an mi portant technology in the land subsidencemeasurement, extraction ofstable pointwise target is a criticalprocedure in long temporalD-InSAR processing chain. Aswe know, now the main two kinds ofmethod have been proposed. One is amplitudemethod that can be performed to model the smi ilar behaviors with phase dispersion with no resolution loss by means of a tmi e series analysis of amplitude data. The other is based on coherence stability that can be computed in the stack of interferograms. The twomethods have their own defects, the former requires aminmi um of30 mi ages to detect the stable pointwise targetprecisely, the latterwill directly lead to lower resolution than the original mi ages. In this paperwe introduce an optmi ized extractionmethod of stable pointwise target combining amplitude and coherence analysis. In this paper, amplitude detection method is first mi plemented and the number of stable pointwise targets is extracted. In the step, the data need to be radiometrically calibrated in order to ensure the mi ages to be comparable. And the experiential threshold ofamplitude dispersion is selected to extractstable pointwise targets. Ami ing atsolving problems of low density and ununiformity distribution of pointwise targets extracted by amplitude detection, amulti-step detection method is proposed. Themulti-step detection method first uses amplitude detection, the proper threshold is selected to extract candidates of stable pointwise targets, which can ensuremost of stable pointwise targets are included and greatly mi prove computation efficiency by the threshold. Further temporal coherence is utilized to extract the precise pointwise targets. In the step, themodelof temporal coherence is established, and the partialatmosphere disturb and orbiterrorare removed by lowpass filters, sequentially the phase caused by the DEM error is estmi ated by a rough search of parameter space, the average effective phase are separated in interferogram stack. As the temporal coherence coefficient is proportional to the number of interferograms, the proper threshold is chosen in terms of the proportional relationship. Lastly, pointwise targets of theirpixelvalue larger than the referred threshold are extracted.W ith themulti-step detection method, more reliable stable pointwise targets are extracted. The evaluation of the method is finally carried outwith 26 ERS-1/2 C-band SAR mi ages acquired over Shanghai urban covering 94 km2from 1992 to 2000. Amplitude detectionmethod andmulti-step detectionmethod are mi plemented at the same region respectively. The effectiveness of two methods is evaluated by the number and density of extracted pointwise targets. By comparison, pointwise targets ofextracted by amplitude detection have the lowerdensity thanmulti step detectionmethod. And reliability is evaluated by testing the target corresponding to the land type. It is known that stable pointwise targetspoints corresponding to the stableman-made objects in the urban. After the ground investigation in shanghai urban, we find themostofextracted points are usually corresponding to stableman-made objects, e. g. building and bridge. It fully validates the reliability ofmulti-step detectionmethod. In summary, the testing results show that the presentedmethod can extract stable pointwise targets effectively and reliably.