第七讲 几何纠正(摄影测量与遥感).pdf

第七讲 遥感数据预处理 几何纠正 第七讲 遥感数据预处理 几何纠正 几何纠正 几何纠正几何纠正 遥感影像一般需要经过几何纠正的预处理去除 像元的几何畸变 使像元回到正确的平面位置 x y 上 遥感影像经过几何纠正后 可以和其它专题信 息 GIS 进行复合分析 从经过几何纠正的遥感影像上可以提取正确的 距离 面积和方位信息 遥感影像一般需要经过几何纠正的预处理去除遥感影像一般需要经过几何纠正的预处理去除 像元的几何畸变 使像元回到正确的平面位置像元的几何畸变 使像元回到正确的平面位置 x x y y 上 上 遥感影像经过几何纠正后 可以和其它专题信遥感影像经过几何纠正后 可以和其它专题信 息 息 GISGIS 进行复合分析 进行复合分析 从经过几何纠正的遥感影像上可以提取正确的从经过几何纠正的遥感影像上可以提取正确的 距离 面积和方位信息距离 面积和方位信息 内部和外部几何误差 系统误差和随机误差 内部和外部几何误差内部和外部几何误差 系统误差和随机误差系统误差和随机误差 几何误差的类型 几何误差的类型几何误差的类型 内部几何误差 内部几何误差 Internal geometric errors 是由遥感系 统本身以及遥感系统成像过程中与地球自转和地球曲率 效应相结合而产生的几何误差 内部几何误差一般属于系统误差 可预测的误差 这 种误差可以通过传感器发射前或飞行过程中传感器系统 与地球的相关几何特征预测 如 由地球自转引起的图像歪斜 扫描系统引起的像元对应的地面实际大小的变化 扫描系统引起的地形水平位移 内部几何误差 内部几何误差 内部几何误差 内部几何误差 Internal geometric errorsInternal geometric errors 是由遥感系是由遥感系 统本身以及遥感系统成像过程中与地球自转和地球曲率统本身以及遥感系统成像过程中与地球自转和地球曲率 效应相结合而产生的几何误差 效应相结合而产生的几何误差 内部几何误差一般属于系统误差 可预测的误差 这内部几何误差一般属于系统误差 可预测的误差 这 种误差可以通过传感器发射前或飞行过程中传感器系统种误差可以通过传感器发射前或飞行过程中传感器系统 与地球的相关几何特征预测 如 与地球的相关几何特征预测 如 由地球自转引起的图像歪斜由地球自转引起的图像歪斜 扫描系统引起的像元对应的地面实际大小的变化扫描系统引起的像元对应的地面实际大小的变化 扫描系统引起的地形水平位移扫描系统引起的地形水平位移 内部几何误差 内部几何误差内部几何误差 地球自转引起的影像歪斜 地球自转引起的影像歪斜地球自转引起的影像歪斜 太阳同步的对地观测微星一般沿着固定的轨道运行 在从北到南的降轨模式时获取图像 地球从西向东每24小时自转一周 卫星从北向南飞行时 地球同时自西向东旋转 造成 图像歪斜 太阳同步的对地观测微星一般沿着固定的轨道运行 太阳同步的对地观测微星一般沿着固定的轨道运行 在从北到南的降轨模式时获取图像 在从北到南的降轨模式时获取图像 地球从西向东每地球从西向东每2424小时自转一周 小时自转一周 卫星从北向南飞行时 地球同时自西向东旋转 造成卫星从北向南飞行时 地球同时自西向东旋转 造成 图像歪斜图像歪斜 a Landsat satellites 4 5 and 7 are in a Sun synchronous orbit with an angle of inclination of 98 2 The Earth rotates on its axis from west to east as imagery is collected b Pixels in three hypothetical scans consisting of 16 lines each of Landsat TM data While the matrix raster may look correct it actually contains systematic geometric distortion caused by the angular velocity of the satellite in its descending orbital path in conjunction with the surface velocity of the Earth as it rotates on its axis while collecting a frame of imagery c The result of adjusting deskewing the original Landsat TM data to the west to compensate for Earth rotation effects Landsats 4 5 and 7 use a bidirectional cross track scanning mirror a a LandsatLandsat satellites 4 5 and 7 are in a Sunsatellites 4 5 and 7 are in a Sun synchronous orbit with an angle of inclination of synchronous orbit with an angle of inclination of 98 298 2 The Earth rotates on its axis from west to The Earth rotates on its axis from west to east as imagery is collected east as imagery is collected b b Pixels in three hypothetical scans consisting of Pixels in three hypothetical scans consisting of 16 lines each of 16 lines each of LandsatLandsat TM data While the TM data While the matrix raster may look correct it actually matrix raster may look correct it actually contains systematic geometric distortion caused by contains systematic geometric distortion caused by the angular velocity of the satellite in its the angular velocity of the satellite in its descending orbital path in conjunction with the descending orbital path in conjunction with the surface velocity of the Earth as it rotates on its axis surface velocity of the Earth as it rotates on its axis while collecting a frame of imagery while collecting a frame of imagery c c The result of adjusting The result of adjusting deskewingdeskewing the original the original LandsatLandsat TM data to the west to compensate for TM data to the west to compensate for Earth rotation effects Earth rotation effects LandsatsLandsats 4 5 and 7 use a 4 5 and 7 use a bidirectional crossbidirectional cross track scanning mirror track scanning mirror 图像歪斜 图像歪斜图像歪斜 扫描系统引起的地面实际分辨率大 小的变化 扫描系统引起的地面实际分辨率大扫描系统引起的地面实际分辨率大 小的变化小的变化 卫星遥感的扫描系统一般在几百公里的高度 只需偏 离星下点很小的角度来获取数据 因此可以减小扫描系 统引起的几何误差 航空遥感系统只是在几公里的高空飞行 因此扫描系 统的总视场角可以达到70 左右 这样就容易引起几何上 的畸变 卫星遥感的扫描系统一般在几百公里的高度 只需偏卫星遥感的扫描系统一般在几百公里的高度 只需偏 离星下点很小的角度来获取数据 因此可以减小扫描系离星下点很小的角度来获取数据 因此可以减小扫描系 统引起的几何误差 统引起的几何误差 航空遥感系统只是在几公里的高空飞行 因此扫描系航空遥感系统只是在几公里的高空飞行 因此扫描系 统的总视场角可以达到统的总视场角可以达到7070 左右 这样就容易引起几何上左右 这样就容易引起几何上 的畸变的畸变 The ground resolution cell size along a single across track scan is a function of a the distance from the aircraft to the observation where H is the altitude of the aircraft above ground level AGL at nadir and H sec off nadir b the instantaneous field of view of the sensor measured in radians and c the scan angle off nadir Pixels off nadir have semi major and semi minor axes diameters that define the resolution cell size The total field of view of one scan line is One dimensional relief displacement and tangential scale distortion occur in the direction perpendicular to the line of flight and parallel with a line scan The The ground resolution cell sizeground resolution cell size along a along a single acrosssingle across track scan is a function of track scan is a function of a the distance from the aircraft to the a the distance from the aircraft to the observation where observation where H H is the altitude of the is the altitude of the aircraft above ground level AGL at aircraft above ground level AGL at nadir and nadir and H secH sec offoff nadir b the nadir b the instantaneousinstantaneous fieldfield ofof view of the view of the sensor sensor measured in radians and c the measured in radians and c the scan angle offscan angle off nadir nadir Pixels offPixels off nadir nadir have semihave semi major and semimajor and semi minor axes minor axes diameters that define the resolution cell diameters that define the resolution cell size The total field of view of one scan size The total field of view of one scan line is line is One One dimensional relief dimensional relief displacement and tangential scale displacement and tangential scale distortion occur in the direction distortion occur in the direction perpendicular to the line of flight and perpendicular to the line of flight and parallel with a line scan parallel with a line scan Ground Swath Width Ground Swath WidthGround Swath Width 航迹交叉 across track 扫描系统的地面幅宽 ground swath width 是扫描镜完全扫过一次覆盖的地面条带的 宽度 航迹交叉扫描系统的地面幅宽是传感器总视场角 和传 感器高度H的函数 其计算公式为 航迹交叉航迹交叉 acrossacross track track 扫描系统的地面幅宽 扫描系统的地面幅宽 ground ground swath widthswath width 是是扫描镜完全扫过一次覆盖的地面条带的扫描镜完全扫过一次覆盖的地面条带的 宽度 宽度 航迹交叉扫描系统的地面幅宽是传感器总视场角航迹交叉扫描系统的地面幅宽是传感器总视场角 和传和传 感器高度感器高度H H的函数 其计算公式为 的函数 其计算公式为 2 2 tan Hgsw 地面幅宽 地面幅宽地面幅宽 90 总视场角的航迹交叉扫描系统在6000 m 高度的地面 幅宽为 9090 总视场角的航迹交叉扫描系统在总视场角的航迹交叉扫描系统在6000 6000 m m 高度的地面高度的地面 幅宽为 幅宽为 26000 2 90 tan gsw 260001 gsw mgsw12000 扫描系统造成的一维地形位移 扫描系统造成的一维地形位移扫描系统造成的一维地形位移 航迹交叉扫描系统会导致地形位移 对每个扫描线 地形位移 发生在垂直与飞行线的方向 在星下点位置 扫描系统垂直向下看 水桶表现为一个 圆 但 在偏离星下点的位置 就会发生水平位移 目标物里局部地形越高 目标物的顶部离星下点越远 一维地 形位移量越大 航迹交叉扫描系统会导致地形位移 对每个扫描线 地形位移航迹交叉扫描系统会导致地形位移 对每个扫描线 地形位移 发生在垂直与飞行线的方向 发生在垂直与飞行线的方向 在星下点位置 扫描系统垂直向下看 水桶表现为一个在星下点位置 扫描系统垂直向下看 水桶表现为一个 圆 但圆 但 在偏离星下点的位置 就会发生水平位移 在偏离星下点的位置 就会发生水平位移 目标物里局部地形越高 目标物的顶部离星下点越远 一维地目标物里局部地形越高 目标物的顶部离星下点越远 一维地 形位移量越大形位移量越大 a Hypothetical perspective geometry of a vertical aerial photograph obtained over level terrain Four 50 ft tall tanks are distributed throughout the landscape and experience varying degrees of radial relief displacement the farther they are from the principal point PP b Across track scanning system introduces one dimensional relief displacement perpendicular to the line of flight and tangential scale distortion and compression the farther the object is from nadir Linear features trending across the terrain are often recorded with s shaped or sigmoid curvature characteristics due to tangential scale distortion and image compression a Hypothetical perspective geometry of a vertical aerial photoga Hypothetical perspective geometry of a vertical aerial photograph obtained over level terrain Four raph obtained over level terrain Four 5050 ft ft tall tanks are distributed throughout the landscape and experientall tanks are distributed throughout the landscape and experience varying degrees of radial relief ce varying degrees of radial relief displacement the farther they are from the principal point PP displacement the farther they are from the principal point PP b Acrossb Across track scanning system track scanning system introduces introduces oneone dimensional relief displacementdimensional relief displacement perpendicular to the line of flight and perpendicular to the line of flight and tangential scale tangential scale distortion and compressiondistortion and compression the farther the object is from nadir Linear features trending the farther the object is from nadir Linear features trending across the across the terrain are often recorded with sterrain are often recorded with s shaped or shaped or sigmoid curvaturesigmoid curvature characteristics due to tangential scale characteristics due to tangential scale distortion and image compression distortion and image compression 扫描系统正切比例尺畸变 Tangential Scale Distortion 扫描系统正切比例尺畸变 扫描系统正切比例尺畸变 Tangential Tangential Scale DistortionScale Distortion 在航迹交叉扫描系统的成像过程中 扫描镜是以常速转动的 由于靠近星下点的目标比偏离星下点的目标离扫描镜更近 而扫 描镜在以常速转动 因此在每条扫描线上 星下点的像元在扫描 线方向的大小比偏离星下点 影像边缘 的小 这对水平于扫描 线的目标实际上是一种 压缩 效应 距离星下点越远 比例尺压 缩效应越明显 这种效应叫做 正切比例尺压缩 总体特征 接近星下点的目标表现为正常形状 远离星下点的 目标被压缩 其现状发生畸变 正切比例尺畸变导致线形特征目标 如道路等 呈现s shape or sigmoid distortion 但对于平行于或垂直于飞行线的线形目标 则不会出现这种情况 在航迹交叉扫描系统的成像过程中 扫描镜是以常速转动的 在航迹交叉扫描系统的成像过程中 扫描镜是以常速转动的 由于靠近星下点的目标比偏离星下点的目标离扫描镜更近 而扫由于靠近星下点的目标比偏离星下点的目标离扫描镜更近 而扫 描镜在以常速转动 因此在每条扫描线上 星下点的像元在扫描描镜在以常速转动 因此在每条扫描线上 星下点的像元在扫描 线方向的大小比偏离星下点 影像边缘 的小 这对水平于扫描线方向的大小比偏离星下点 影像边缘 的小 这对水平于扫描 线的目标实际上是一种线的目标实际上是一种 压缩压缩 效应 距离星下点越远 比例尺压效应 距离星下点越远 比例尺压 缩效应越明显 这种效应叫做缩效应越明显 这种效应叫做 正切比例尺压缩 正切比例尺压缩 总体特征 接近星下点的目标表现为正常形状 远离星下点的总体特征 接近星下点的目标表现为正常形状 远离星下点的 目标被压缩 其现状发生畸变 目标被压缩 其现状发生畸变 正切比例尺畸变导致线形特征目标 如道路等 呈现正切比例尺畸变导致线形特征目标 如道路等 呈现s s shapeshape or or sigmoid distortionsigmoid distortion 但对于平行于或垂直于飞行线的线形目标 但对于平行于或垂直于飞行线的线形目标 则不会出现这种情况 则不会出现这种情况 a Hypothetical perspective geometry of a vertical aerial photograph obtained over level terrain Four 50 ft tall tanks are distributed throughout the landscape and experience varying degrees of radial relief displacement the farther they are from the principal point PP b Across track scanning system introduces one dimensional relief displacement perpendicular to the line of flight and tangential scale distortion and compression the farther the object is from nadir Linear features trending across the terrain are often recorded with s shaped or sigmoid curvature characteristics due to tangential scale distortion and image compression a Hypothetical perspective geometry of a vertical aerial photoga Hypothetical perspective geometry of a vertical aerial photograph obtained over level terrain Four raph obtained over level terrain Four 5050 ft ft tall tanks are distributed throughout the landscape and experientall tanks are distributed throughout the landscape and experience varying degrees of radial relief ce varying degrees of radial relief displacement the farther they are from the principal point PP displacement the farther they are from the principal point PP b Acrossb Across track scanning system track scanning system introduces introduces oneone dimensional relief displacementdimensional relief displacement perpendicular to the line of flight and perpendicular to the line of flight and tangential scale tangential scale distortion and compressiondistortion and compression the farther the object is from nadir Linear features trending the farther the object is from nadir Linear features trending across the across the terrain are often recorded with terrain are often recorded with s s shaped or sigmoid curvature characteristics due to tangential scshaped or sigmoid curvature characteristics due to tangential scale ale distortion and image compression distortion and image compression 外部几何误差 External geometric errors 外部几何误差 外部几何误差 External External geometric errorsgeometric errors 外部几何误差一般由随时空发生变化的外部因素引起 引起遥感影像外部几何误差的主要因素是成像是传感器 平台的姿态和位置 包括 高度变化 姿态变化 滚动 仰伏 外部几何误差一般由随时空发生变化的外部因素引起 外部几何误差一般由随时空发生变化的外部因素引起 引起遥感影像外部几何误差的主要因素是成像是传感器引起遥感影像外部几何误差的主要因素是成像是传感器 平台的姿态和位置 包括 平台的姿态和位置 包括 高度高度变化变化 姿态姿态变化变化 滚动 仰伏滚动 仰伏 高度变化 高度变化高度变化 理想状态下 遥感系统在离地面固定的高度飞行 以保证整个航迹上影像比例 尺一致 如果飞行过程中飞机航高发生变化 影像的比例尺就会发生变化 The diameter of the spot size on the ground D the nominal spatial resolution is a function of the instantaneous field of view and the altitude above ground level H of the sensor system i e 理想状态下 遥感系统在离地面固定的高度飞行 以保证整个航迹上影像比例理想状态下 遥感系统在离地面固定的高度飞行 以保证整个航迹上影像比例 尺一致 尺一致 如果飞行过程中飞机航高发生变化 影像的比例尺就会发生变化如果飞行过程中飞机航高发生变化 影像的比例尺就会发生变化 The The diameter of the spot size on the grounddiameter of the spot size on the ground D D the nominal spatial resolution is a the nominal spatial resolution is a function of the function of the instantaneousinstantaneous fieldfield ofof viewview and the and the altitude above ground levelaltitude above ground level H H of the sensor system i e of the sensor system i e HD a Geometric modification in imagery may be introduced by changes in the aircraft or satellite platform altitude above ground level AGL at the time of data collection Increasing altitude results in smaller scale imagery while decreasing altitude results in larger scale imagery b Geometric modification may also be introduced by aircraft or spacecraft changes in attitude including roll pitch and yaw An aircraft flies in the x direction Roll occurs when the aircraft or spacecraft fuselage maintains directional stability but the wings move up or down i e they rotate about the x axis angle omega Pitch occurs when the wings are stable but the fuselage nose or tail moves up or down i e they rotate about the y axis angle phi Yaw occurs when the wings remain parallel but the fuselage is forced by wind to be oriented some angle to the left or right of the intended line of flight i e it rotates about the z axis angle kappa Thus the plane flies straight but all remote sensor data are displaced by Remote sensing data often are distorted due to a combination of changes in altitude and attitude roll pitch and yaw a Geometric modification in imagery may a Geometric modification in imagery may be introduced by changes in the aircraft or be introduced by changes in the aircraft or satellite platform satellite platform altitudealtitude above ground above ground level AGL at the time of data collection level AGL at the time of data collection Increasing altitude results in smallerIncreasing altitude results in smaller scale scale imagery while decreasing altitude results in imagery while decreasing altitude results in largerlarger scale imagery scale imagery b Geometric modification may also be b Geometric modification may also be introduced by aircraft or spacecraft changes introduced by aircraft or spacecraft changes in in attitudeattitude including including rollroll pitchpitch and and yawyaw An aircraft flies in the An aircraft flies in the x x direction direction RollRoll occurs when the aircraft or spacecraft occurs when the aircraft or spacecraft fuselage maintains directional stability but fuselage maintains directional stability but the wings move up or down i e they rotate the wings move up or down i e they rotate about the about the x x axis angle omega axis angle omega PitchPitch occurs when the wings are stable but the occurs when the wings are stable but the fuselage nose or tail moves up or down i e fuselage nose or tail moves up or down i e they rotate about thethey rotate about the y y axis angle phi axis angle phi YawYaw occurs when the wings remain parallel occurs when the wings remain parallel but the fuselage is forced by wind to be but the fuselage is forced by wind to be oriented some angle to the left or right of the oriented some angle to the left or right of the intended line of flight i e it rotates about intended line of flight i e it rotates about the zthe z axis angle kappa axis angle kappa Thus the plane Thus the plane flies straight but all remote sensor data are flies straight but all remote sensor data are displaced by displaced by Remote sensing data often Remote sensing data often are distorted due to a combination of are distorted due to a combination of changes in changes in altitudealtitude and and attitudeattitude roll pitch roll pitch and yaw and yaw 姿态变化 姿态变化姿态变化 卫星遥感平台的姿态相对比较稳定 因为它受大气湍流和风的 影响比较小 对于航空遥感平台 由于受许多外部因素的作用 会随机发生各种姿态的变化 包括 滚动 roll 仰伏 pitch and yaw 等 因此遥感系统一般都配备特别的姿态稳定 系统来稳定传感器的姿态 由于传感器姿态变化导致的遥感影像的几何误差只能通过地面 控制点进行纠正 卫星遥感平台的姿态相对比较稳定 因为它受大气湍流和风的卫星遥感平台的姿态相对比较稳定 因为它受大气湍流和风的 影响比较小 对于航空遥感平台 由于受许多外部因素的作用 影响比较小 对于航空遥感平台 由于受许多外部因素的作用 会随机发生各种姿态的变化 包括会随机发生各种姿态的变化 包括 滚动 滚动 rollroll 仰伏 仰伏 pitchpitch and and yawyaw 等 因此遥感系统一般都配备特别的姿态稳定 等 因此遥感系统一般都配备特别的姿态稳定 系统来稳定传感器的姿态 系统来稳定传感器的姿态 由于传感器姿态变化导致的遥感影像的几何误差只能通过地面由于传感器姿态变化导致的遥感影像的几何误差只能通过地面 控制点进行纠正 控制点进行纠正 a Geometric modification in imagery may be introduced by changes in the aircraft or satellite platform altitude above ground level AGL at the time of data collection Increasing altitude results in smaller scale imagery while decreasing altitude results in larger scale imagery b Geometric modification may also be introduced by aircraft or spacecraft changes in attitude including roll pitch and yaw An aircraft flies in the x direction Roll occurs when the aircraft or spacecraft fuselage maintains directional stability but the wings move up or down i e they rotate about the x axis angle omega Pitch occurs when the wings are stable but the fuselage nose or tail moves up or down i e they rotate about the y axis angle phi Yaw occurs when the wings remain parallel but the fuselage is forced by wind to be oriented some angle to the left or right of the intended line of flight i e it rotates about the z axis angle kappa Thus the plane flies straight but all remote sensor data are displaced by Remote sensing data often are distorted due to a combination of changes in altitude and attitude roll pitch and yaw a Geometric modification in imagery may a Geometric modification in imagery may be introduced by changes in the aircraft or be introduced by changes in the aircraft or satellite platform satellite platform altitudealtitude above ground above ground level AGL at the time of data collection level AGL at the time of data collection Increasing altitude results in smallerIncreas