THE EFFECT OF TOPOGRAPHY ON SAR CALIBRATION
THE EFFECT OF TOPOGRAPHY ON SAR CALIBRATION
复制标题
DOI：
10.1117/12.140622
复制
发表时间：
1993-09-01
影响因子：
8.2
通讯作者：
SHI, JC
中科院分区：
文献类型：
--
作者：
VANZYL, JJ;CHAPMAN, BD;SHI, JC
在合成孔径雷达（SAR）处理过程中，当进行辐射校正（如天线方向图和散射区域去除）时，假设有一个Rat地球。在这里，我们研究地形变化对这些修正的影响。局部坡度将导致实际散射面积与使用平坦地球假设计算的散射面积不同。结果表明，这种影响，这是目前的机载和星载SAR数据，很容易导致校准误差大于分贝。在天线方向图去除过程中忽略地形也会在机载系统中引入几分贝的误差。地形对天线方向图去除的影响预计是可以忽略不计的星载SAR的。在本文中，我们将展示如何考虑这些影响，如果一个数字高程模型可用于成像区域。两种不同类型的地形，一个温和的救济区附近的墓碑，亚利桑那州，和一个高救济区附近的奥地利阿尔卑斯山的Oetztal的错误进行量化。我们展示了两个著名的雷达系统，C波段ERS-1星载雷达系统和三频NASA/JPL机载SAR系统（AIRSAR）的错误。对于中等起伏的区域，它示出，散射区域去除导致的误差是小于1 dB的图像中的大部分，虽然误差的航天器的情况下是大于那些的机载情况下，主要是因为较小的入射角。在高起伏区域的情况下，即使在空气传播的情况下，大多数的主要斜率显示出5 dB或更大的误差。在Oetztal地区的星载例子中，大部分图像显示的误差超过1 dB，大部分区域显示的误差幅度超过5 dB。使用AIRSAR的C波段天线方向图，它表明，非常大的误差，一些远远大于10分贝，可以预期在附近的范围内的Oetztal图像。它还表明，不考虑地形在天线方向图去除过程中引入极化校准误差。
During normal synthetic aperture radar (SAR) processing, a Rat earth is assumed when performing radiometric corrections such as antenna pattern and scattering area removal. Here we examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering area to be different from that calculated using the flat earth assumption. It is shown that this effect, which is present for both airborne and spaceborne SAR data, may easily cause calibration errors larger than a decibel. Ignoring the topography during antenna pattern removal mag also introduce errors of several decibels in the case of airborne systems. The effect of topography on antenna pattern removal is expected to be negligible for spaceborne SAR's.In this paper we show how these effects can be taken into account if a digital elevation model is available for the imaged area. The errors are quantified for two different types of terrain, a moderate relief area near Tombstone, AZ, and a high relief area near Oetztal in the Austrian Alps. We show errors for two well-known radar systems, the C-band ERS-1 spaceborne radar system and the three frequency NASA/JPL airborne SAR system (AIRSAR). For the moderate relief area, it is shown that the scattering area removal leads to errors that are smaller than 1 dB in most of the image, although the errors for the spaceborne case are larger than those of the airborne case, mainly because of the smaller incidence angle. In the case of the high relief area, most of the leading slopes show errors on the order of 5 dB or larger, even in the airborne case. In the spaceborne example of the Oetztal area, most of the image shows errors exceeding 1 dB, with large areas showing errors exceeding 5 dB in magnitude. Using the AIRSAR C-band antenna pattern, it is shown that extremely large errors, some well larger than 10 dB can be expected in the near range of the Oetztal image. It is also shown that not taking the topography into account during antenna pattern removal introduces polarimetric calibration errors.