利用Radarsat立体影像提取DEM摄影测量方法研究
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摘要
合成孔径雷达(SAR)是一种工作在微波波段的主动式传感器，能够全天候、全天时地对地观测，并具有一定的穿透能力，具有传统光学摄影机和光电传感器无法比拟的优点。对于那些常年多云雾、多阴雨、植被覆盖茂密致使光学和光电成像困难地区的测绘工作，SAR技术提供了一种新的解决途径。
Radarsat是加拿大于1995年11月4日发射入轨的合成孔径雷达卫星，能够异轨获取立体影像，如何利用这一丰富的SAR影像资源来完成传统光学摄影测量无法完成的测绘任务，是摄影测量工作者面临的新的挑战。
本文主要侧重点是利用立体雷达影像提取DEM的方法研究。文章首先简要分析了SAR成像原理，SAR影像特征和由SAR影像构建立体模型的特点，并对SAR影像构像模型进行了比较和分析。根据现有资料情况，确定了采用等效线中心投影的构像模型作为几何处理的数学基础。根据该模型，本文采用单像空间后方交会和双像空间前方交会相结合的方法来解求地面点空间坐标。即首先利用地面控制点通过单像空间后方交会解算影像的外方位元素，在匹配得到同名像点的影像坐标后，通过双像前方交会逐点解算地面点空间三维坐标，最后对解算结果进行内插获得规则的DEM，完成了从立体影像到DEM的整个流程。
外方位元素的解算，是解析处理的一个难点，本文采用线元素和角元素分开迭代计算的方法来控制线角元素的相关性，计算得到方位元素。由SAR影像构建的立体模型与由中心投影影像构建的立体模型不同，有其自身的特点，本文采用空间交会和迭代计算相结合的方法来实现双像解析计算，求得地面点的空间坐标。
本文以Radarsat立体影像为实验数据，应用上述方法进行处理，获取了实验区的DEM，实验结果验证了本文所提出的方法的正确性，也说明利用Radarsat立体影像提取DEM和测制地形图技术上是可行的，这给我国西部光学成像困难地区的测绘工作提供了一种新思路和新方法。
As a kind of positive sensor working with microwave, Synthetic Aperture Radar (SAR), which has the capacity of penetrating clouds to some extent, can observe the earth day and night and whole weather. It has some advantages that traditional optical and optoelectronic camera does not possess. SAR technology provide a new way to the topography mapping in the cloudy, rainy, and vegetate-covered areas.
Radarsat is a SAR satellite launched in November 14, 1995 by Canada. It can obtain the SAR stereo images in two orbits. How to make use of the abundant SAR image resources to accomplish the task in which the traditional photogrammetry can't succeed is a challenge faced with us.
The main emphasis of this paper is the study on the methodology of generating DEM from Radarsat image stereo pairs. In this paper , the principle of SAR formation image is briefly analysed firstly, the features of SAR image and specalities of stereo model made by SAR image pairs are discussed, three kinds of SAR image formation model are compared and analysed. According to the image data possessed, the formation model of equivalent line central projection is adopted to establish the correspondence between image and object space. Based on this model, every point's object space coordinates are calculated by space resection and space intersection. The exterior orientation elements are calculated by single image space resection with GCPs, and the object space coordinates are calculated by double image space intersection. The grid DEM is produced by interpolation. This is the whole flow of generating DEM from SAR stereo images.
The calculation of exterior orientation elements is the difficult point of analytical treatment. The algorithm is adopted to overcome the correlation between the exterior orientation elements, in which the linear elements and angular elements are separated into two parts to iterative calculate. Because the SAR stereo model is different from optical image stereo model, the object space coordinates of ground points are calculated by iterative space iteration.
The Radarsat image stereo pairs are used as experiment data in this paper. The DEM of test area is generated by using above-mentioned methods. The results of experiment
show that the methodology adopted in this paper is correct, and prove that generating DEM from Radarsat stereo images is practical. This provide a new thought and way for topography mapping in western China.
Radarsat是加拿大于1995年11月4日发射入轨的合成孔径雷达卫星，能够异轨获取立体影像，如何利用这一丰富的SAR影像资源来完成传统光学摄影测量无法完成的测绘任务，是摄影测量工作者面临的新的挑战。
本文主要侧重点是利用立体雷达影像提取DEM的方法研究。文章首先简要分析了SAR成像原理，SAR影像特征和由SAR影像构建立体模型的特点，并对SAR影像构像模型进行了比较和分析。根据现有资料情况，确定了采用等效线中心投影的构像模型作为几何处理的数学基础。根据该模型，本文采用单像空间后方交会和双像空间前方交会相结合的方法来解求地面点空间坐标。即首先利用地面控制点通过单像空间后方交会解算影像的外方位元素，在匹配得到同名像点的影像坐标后，通过双像前方交会逐点解算地面点空间三维坐标，最后对解算结果进行内插获得规则的DEM，完成了从立体影像到DEM的整个流程。
外方位元素的解算，是解析处理的一个难点，本文采用线元素和角元素分开迭代计算的方法来控制线角元素的相关性，计算得到方位元素。由SAR影像构建的立体模型与由中心投影影像构建的立体模型不同，有其自身的特点，本文采用空间交会和迭代计算相结合的方法来实现双像解析计算，求得地面点的空间坐标。
本文以Radarsat立体影像为实验数据，应用上述方法进行处理，获取了实验区的DEM，实验结果验证了本文所提出的方法的正确性，也说明利用Radarsat立体影像提取DEM和测制地形图技术上是可行的，这给我国西部光学成像困难地区的测绘工作提供了一种新思路和新方法。
As a kind of positive sensor working with microwave, Synthetic Aperture Radar (SAR), which has the capacity of penetrating clouds to some extent, can observe the earth day and night and whole weather. It has some advantages that traditional optical and optoelectronic camera does not possess. SAR technology provide a new way to the topography mapping in the cloudy, rainy, and vegetate-covered areas.
Radarsat is a SAR satellite launched in November 14, 1995 by Canada. It can obtain the SAR stereo images in two orbits. How to make use of the abundant SAR image resources to accomplish the task in which the traditional photogrammetry can't succeed is a challenge faced with us.
The main emphasis of this paper is the study on the methodology of generating DEM from Radarsat image stereo pairs. In this paper , the principle of SAR formation image is briefly analysed firstly, the features of SAR image and specalities of stereo model made by SAR image pairs are discussed, three kinds of SAR image formation model are compared and analysed. According to the image data possessed, the formation model of equivalent line central projection is adopted to establish the correspondence between image and object space. Based on this model, every point's object space coordinates are calculated by space resection and space intersection. The exterior orientation elements are calculated by single image space resection with GCPs, and the object space coordinates are calculated by double image space intersection. The grid DEM is produced by interpolation. This is the whole flow of generating DEM from SAR stereo images.
The calculation of exterior orientation elements is the difficult point of analytical treatment. The algorithm is adopted to overcome the correlation between the exterior orientation elements, in which the linear elements and angular elements are separated into two parts to iterative calculate. Because the SAR stereo model is different from optical image stereo model, the object space coordinates of ground points are calculated by iterative space iteration.
The Radarsat image stereo pairs are used as experiment data in this paper. The DEM of test area is generated by using above-mentioned methods. The results of experiment
show that the methodology adopted in this paper is correct, and prove that generating DEM from Radarsat stereo images is practical. This provide a new thought and way for topography mapping in western China.
引文
[1]郭华东，雷达对地观测理论与应用，科学出版社，2000．
[2]舒宁，微波遥感原理，武汉大学出版社，2000．
[3]魏钟铨，合成孔径雷达卫星，科学出版社，2001．
[4]刘永坦，雷达成像技术，哈尔滨工业大学出版社，1999．
[5]袁孝康，星载合成孔径雷达导论，国防工业出版社，2003．
[6]肖国超、朱彩云，雷达摄影测量，地震出版社，2001．
[7]王之卓，摄影测量原理，测绘出版社，1984．
[8]李德仁、周月琴、金为铣，摄影测量与遥感概论，测绘出版社，2001．
[9]金为铣、杨先宏、邵鸿潮等，摄影测量学，武汉测绘科技大学出版社，1999．
[10]孙家捅、舒宁、关泽群，遥感原理、方法和应用，测绘出版社，1997．
[11]雷达摄影测量译文专辑，测绘情报(增刊)，1992．
[12]肖国超，SAR图像纠正的数学模型，解放军测绘学院学报，1994(3)．
[13]周月琴等，SAR图像立体定位原理与精度分析，遥感学报，1998(4)．
[14]李晶，利用SAR图像制作正射影像图的研究[硕士论文]，郑州：郑州解放军测绘学院，1996．4．
[15]倪秀平、肖国超、万志龙，SAR影像窗初始行外方位元素的求解法，国土资源遥感，1997(3)．
[16]时富生，合成孔径立体雷达图像解析法的研究，军测科技，1989(2)．
[17]张祖勋、周月琴，SPOT卫星图像外方位元素的解求，武测科技，1998(2)．
[18]张永红，合成孔径雷达成像几何机理分析及处理方法研究[博士论文]， 武汉：武汉大学，2001．5．
[19]张永红、林宗坚、张继贤、甘梦龙，SAR影像几何校正，测绘学报，2002(5)．
[20]燕琴， 异轨遥感影像的外方位元素解求[硕士论文]， 武汉：武汉测绘科技大学，2000．4．
[21]张森林，像片外方位元素计算中线性元素和角元素之间强相关的克服， 武汉：武测科技，1987(4)．
[22]黄玉琪，基于岭估计的SPOT影像外方位元素的解算方法，解放军测绘学院学报，1998(3)．
[23]方勇、常本义、胡文颂等，从多传感器SAR影像提取DEM．
[24]李晶、邵永社，利用SAR图像制作正射影像图的研究，解放军测绘学院学报，1997(2)．
[25] 刘凤德、邱懿、李健，JX—4A全数字摄影测量工作站中IKONOS立体影像的处理方法与应用，遥感信息，2001(4)．
[26] 刘玉贤，利用DEM进行星载SAR影像的几何精纠正，测绘科技动态，1994(3)．
[27] G. Konecny, W. Schuhr. Reliability of Radar Image Data. ISPRS Comm.I symposium, 1988.
[28] H.Rosenfield, Stereo Radar Techniques -Optimum flight configuration for Side Looking Airbone Radar[C], Semi-Annual Convention of American Society of Photogrammetey, October 1967.
[29] J.Bryan Mercer, Scott Thornton, and Keith Tennant, Operational DEM production from Airbone Interferometry and from RADARSAT Stereo Technologies[C], 1998 ASPRS-RTI Annual Conference, 1998.
[30] T. Toutin, Generating DEM from stereo images with a photogrammetric approach: Examples with VIR and SAR data[J]. EARSeL Journal Advances in Remote Sensing, Vol. 4, no. 2, pp. 110-117, 1995.
[31] T. Toutin, Error Tracking of Radargrammetric DEM from RADARSAT Images,IEEE Transactions on Geoscience and Remote Sensing, Vol.37,No.5,1999.
[32] T. Toutin. Evaluation of Radargrammetric DEM from RADARSAT Images in High Relief Areas. IEEE Transactions on Geoscience and Remote Sensing, Voi.38,No.2,2000.
[33] Michele Crosetto, Femando Perez Aragues, Radargrammetry and SAR interferometry for DEM generation : validation and data fusion[J].
[34] Marty Marra, Kelly E.Mautice, Dennis C.Ghiglia, etl. Automated DEM Extraction Using RADARSAT ScanSAR Stereo Data. 1EEE, 1998.
[35] Min-Ho Ka and Man-Jo Kim, Digital Elevation Map Generation using SAR Stereo Technique with Radarsat Image over Seoul Area[J], Korean Journal of Remote Sensing, Vol.17, No.2, 2001.
[2]舒宁，微波遥感原理，武汉大学出版社，2000．
[3]魏钟铨，合成孔径雷达卫星，科学出版社，2001．
[4]刘永坦，雷达成像技术，哈尔滨工业大学出版社，1999．
[5]袁孝康，星载合成孔径雷达导论，国防工业出版社，2003．
[6]肖国超、朱彩云，雷达摄影测量，地震出版社，2001．
[7]王之卓，摄影测量原理，测绘出版社，1984．
[8]李德仁、周月琴、金为铣，摄影测量与遥感概论，测绘出版社，2001．
[9]金为铣、杨先宏、邵鸿潮等，摄影测量学，武汉测绘科技大学出版社，1999．
[10]孙家捅、舒宁、关泽群，遥感原理、方法和应用，测绘出版社，1997．
[11]雷达摄影测量译文专辑，测绘情报(增刊)，1992．
[12]肖国超，SAR图像纠正的数学模型，解放军测绘学院学报，1994(3)．
[13]周月琴等，SAR图像立体定位原理与精度分析，遥感学报，1998(4)．
[14]李晶，利用SAR图像制作正射影像图的研究[硕士论文]，郑州：郑州解放军测绘学院，1996．4．
[15]倪秀平、肖国超、万志龙，SAR影像窗初始行外方位元素的求解法，国土资源遥感，1997(3)．
[16]时富生，合成孔径立体雷达图像解析法的研究，军测科技，1989(2)．
[17]张祖勋、周月琴，SPOT卫星图像外方位元素的解求，武测科技，1998(2)．
[18]张永红，合成孔径雷达成像几何机理分析及处理方法研究[博士论文]， 武汉：武汉大学，2001．5．
[19]张永红、林宗坚、张继贤、甘梦龙，SAR影像几何校正，测绘学报，2002(5)．
[20]燕琴， 异轨遥感影像的外方位元素解求[硕士论文]， 武汉：武汉测绘科技大学，2000．4．
[21]张森林，像片外方位元素计算中线性元素和角元素之间强相关的克服， 武汉：武测科技，1987(4)．
[22]黄玉琪，基于岭估计的SPOT影像外方位元素的解算方法，解放军测绘学院学报，1998(3)．
[23]方勇、常本义、胡文颂等，从多传感器SAR影像提取DEM．
[24]李晶、邵永社，利用SAR图像制作正射影像图的研究，解放军测绘学院学报，1997(2)．
[25] 刘凤德、邱懿、李健，JX—4A全数字摄影测量工作站中IKONOS立体影像的处理方法与应用，遥感信息，2001(4)．
[26] 刘玉贤，利用DEM进行星载SAR影像的几何精纠正，测绘科技动态，1994(3)．
[27] G. Konecny, W. Schuhr. Reliability of Radar Image Data. ISPRS Comm.I symposium, 1988.
[28] H.Rosenfield, Stereo Radar Techniques -Optimum flight configuration for Side Looking Airbone Radar[C], Semi-Annual Convention of American Society of Photogrammetey, October 1967.
[29] J.Bryan Mercer, Scott Thornton, and Keith Tennant, Operational DEM production from Airbone Interferometry and from RADARSAT Stereo Technologies[C], 1998 ASPRS-RTI Annual Conference, 1998.
[30] T. Toutin, Generating DEM from stereo images with a photogrammetric approach: Examples with VIR and SAR data[J]. EARSeL Journal Advances in Remote Sensing, Vol. 4, no. 2, pp. 110-117, 1995.
[31] T. Toutin, Error Tracking of Radargrammetric DEM from RADARSAT Images,IEEE Transactions on Geoscience and Remote Sensing, Vol.37,No.5,1999.
[32] T. Toutin. Evaluation of Radargrammetric DEM from RADARSAT Images in High Relief Areas. IEEE Transactions on Geoscience and Remote Sensing, Voi.38,No.2,2000.
[33] Michele Crosetto, Femando Perez Aragues, Radargrammetry and SAR interferometry for DEM generation : validation and data fusion[J].
[34] Marty Marra, Kelly E.Mautice, Dennis C.Ghiglia, etl. Automated DEM Extraction Using RADARSAT ScanSAR Stereo Data. 1EEE, 1998.
[35] Min-Ho Ka and Man-Jo Kim, Digital Elevation Map Generation using SAR Stereo Technique with Radarsat Image over Seoul Area[J], Korean Journal of Remote Sensing, Vol.17, No.2, 2001.
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