航空重力测量中数字滤波器的设计与应用

根据航空重力测量的要求以及滤波器的性能特点, 选择设计了适用于航空重力测量中ＧＰＳ高精度确定垂直扰动加速度的ＦＩＲ 低通滤波器和ＦＩＲ 低通微分器。并通过模拟数据的检测, 证明所设计的滤波器质量令人满意。     

航空重力测量中数字滤波技术的设计与应用

本文依据契比雷夫逼近理论设计了适用于航空重力测量数据处理的ＦＩＲ低通滤波器和ＦＩＲ低通差分器，根据航空重力测量的特点设计了航空重力测量数据的数字滤波处理框图，     

航空重力测量中低通滤波器参数的优选

从含有大量噪声的航空重力仪测量值中提取重力场信息，最常用的方法是使用低通滤波器，欲获得性能优良的滤波器，必须合理地选择滤波器的设计参数。文中利用一组实测GPS数据，讨论了滤波器长度，截止频率，权函数等参数对滤波效果的影响，给出了航空重力测量应用中滤波器参数的若干选择原则。     

航空重力测量对飞机定位数据的精度要求

差分动态ＧＰＳ（ＤＧＰＳ）定位系统的发展给航空重力测量的研究活动注入了新的活力。本文依据我国目前航空重力测量的总体技术指标，讨论了航空重力测量对ＧＰＳ数据的精度要求，并与目前ＧＰＳ所能达到的精度作了比较，结果表明：ＧＰＳ已能基本满足航空重力测量所需的精度要求，但为精确确定垂直扰动加速度必须结合应用高质量的数字滤波器。     

滤波器的截止频率对航空重力测量精度的影响

简要介绍了航空重力测量中滤波器截止频率频率和测量成果精度的关系,结合2012年某地区的实际测量数据分析了滤波器不同的截止频率对航空重力测量的精度的影响。实际数据验证表明,在飞机速度平均为200km/h时,滤波器截止频率为0.007的内符合精度可以达到±6.9978mGal,其精度符合规范要求,表明在航空重力测量的计算中,根据飞机的实际速度确定合适的滤波器截止频率进行滤波,可以有效提高测量的精度。     

航空重力测量中低通滤波器参数的优选

从含有大量噪声的航空重力仪测量值中提取重力场信息,最常用的方法是使用低通滤波器.欲获得性能优良的滤波器,必须合理地选择滤波器的设计参数.文中利用一组实测GPS数据,讨论了滤波器长度、截止频率、权函数等参数对滤波效果的影响,给出了航空重力测量应用中滤波器参数的若干选择原则.     

航空矢量重力测量中有限冲激响应低通数字滤波器的设计

基于窗函数法和切比雪夫逼近法设计了两类适用于航空矢量重力测量的有限冲激响应(FIR)低通数字滤波器。先采用模拟高度数据验证了滤波器的性能,然后对实测静态GPS数据进行了低通滤波处理,并详细分析了滤波器的相位延迟和边界效应等影响。结果表明:①在相同的设计指标下,依照切比雪夫逼近法所设计的滤波器比采用窗函数法设计的滤波器具有更好的低通滤波效果;②对于静态ＧＰＳ测量数据,依照切比雪夫逼近法所设计的滤波器能以±（１～２）ｍＧａｌ（１ｍＧａｌ＝１０－５　ｍ／ｓ２）的精度确定垂直加速度,以优于±１ｍＧａｌ的精度确定水平加速度     

三、P22 大地测量学

CH991720 航空重力测量中数字滤波器的设计与应用/李珊珊(郑州测绘学院)∥解放军测绘学院学报.—1999,16(2).—83～85,89如何由 GPS 测量数据获得高精度的垂直扰动加速度,从而从整个重力仪的输出中分离出地球重力场信息,是保证亳伽级航空重力测量顺利实施的关键。由 DGPS 测定的高程或速度取二阶或一阶微分导出飞机的垂直扰动加速度是一个滤波过程。根据航空重力测量的要求,以及滤波器的     

顾及误差频谱特性的CHZ重力仪航空应用研究

给出了航空重力测量误差频域分析的方法,利用功率谱密度从频域分析了航空标量重力测量系统恢复重力场的能力及影响因素。介绍了CHZ重力仪的主要特点,并利用实测空中重力异常数据及机载GPS动态加速度数据,结合航空重力测量的频谱范围,分析了CHZ重力仪在不同阻尼系数下的动态性能。计算结果表明,采用合适的阻尼系数,CHZ重力仪能够被用于固定翼飞机的航空重力测量。     

航空重力测量的滤波处理及最佳波长分辨率的探讨

根据航空重力测量的数据性质，对其滤波处理中最佳滤长分辨率的确定，提出了一种采用静态飞行数据进行检测的方法－即利用静态飞行数据处理后的重力异常误差平方和最小的原则。并对其在航空重力测量中的必要性做了检验和说明。     

Space-Wise approach for airborne gravity data modelling

Regional gravity field modelling by means of remove-compute-restore procedure is nowadays widely applied in different contexts: it is the most used technique for regional gravimetric geoid determination, and it is also used in exploration geophysics to predict grids of gravity anomalies (Bouguer, free-air, isostatic, etc.), which are useful to understand and map geological structures in a specific region. Considering this last application, due to the required accuracy and resolution, airborne gravity observations are usually adopted. However, due to the relatively high acquisition velocity, presence of atmospheric turbulence, aircraft vibration, instrumental drift, etc., airborne data are usually contaminated by a very high observation error. For this reason, a proper procedure to filter the raw observations in both the low and high frequencies should be applied to recover valuable information. In this work, a software to filter and grid raw airborne observations is presented: the proposed solution consists in a combination of an along-track Wiener filter and a classical Least Squares Collocation technique. Basically, the proposed procedure is an adaptation to airborne gravimetry of the Space-Wise approach, developed by Politecnico di Milano to process data coming from the ESA satellite mission GOCE. Among the main differences with respect to the satellite application of this approach, there is the fact that, while in processing GOCE data the stochastic characteristics of the observation error can be considered a-priori well known, in airborne gravimetry, due to the complex environment in which the observations are acquired, these characteristics are unknown and should be retrieved from the dataset itself. The presented solution is suited for airborne data analysis in order to be able to quickly filter and grid gravity observations in an easy way. Some innovative theoretical aspects focusing in particular on the theoretical covariance modelling are presented too. In the end, the goodness of the procedure is evaluated by means of a test on real data retrieving the gravitational signal with a predicted accuracy of about 0.4 mGal.     

Flight test results from a strapdown airborne gravity system

In June 1995, a flight test was carried out over the Rocky Mountains to assess the accuracy of airborne gravity for geoid determination. The gravity system consisted of a strapdown inertial navigation system (INS), two GPS receivers with zero baseline on the airplane and multiple GPS master stations on the ground, and a data logging system. To the best of our knowledge, this was the first time that a strapdown INS has been used for airborne gravimetry. The test was designed to assess repeatability as well as accuracy of airborne gravimetry in a highly variable gravity field. An east-west profile of 250 km across the Rocky Mountains was chosen and four flights over the same ground track were made. The flying altitude was about 5.5km, i.e., between 2.5 and 5.0km above ground, and the average flying speed was about 430km/h. This corresponds to a spatial resolution (half wavelength of cutoff frequency) of 5.07.0km when using filter lengths between 90 and 120s. This resolution is sufficient for geoid determination, but may not satisfy other applications of airborne gravimetry. The evaluation of the internal and external accuracy is based on repeated flights and comparison with upward continued ground gravity using a detailed terrain model. Gravity results from repeated flight lines show that the standard deviation between flights is about 2mGal for a single profile and a filter length of 120s, and about 3mGal for a filter length of 90s. The standard deviation of the difference between airborne gravity upward continued ground gravity is about 3mGal for both filter lengths. A critical discussion of these results and how they relate to the different transfer functions applied, is given in the paper. Two different mathematical approaches to airborne scalar gravimetry are applied and compared, namely strapdown inertial scalar gravimetry (SISG) and rotation invariant scalar gravimetry (RISG). Results show a significantly better performance of the SISG approach for a strapdown INS of this accuracy class. Because of major differences in the error model of the two approaches, the RISG method can be used as an effective reliability check of the SISG method. A spectral analysis of the residual errors of the flight profiles indicates that a relative geoid accuracy of 23cm over distances of 200km (0.1 ppm) can be achieved by this method. Since these results present a first data analysis, it is expected that further improvements are possible as more refined modelling is applied. Received: 19 August 1996 / Accepted: 12 May 1997     

New results in airborne vector gravimetry using strapdown INS/DGPS

A method for airborne vector gravimetry has been developed. The method is based on developing the error dynamics equations of the INS in the inertial frame where the INS system errors are estimated in a wave estimator using inertial GPS position as update. Then using the error-corrected INS acceleration and the GPS acceleration in the inertial frame, the gravity disturbance vector is extracted. In the paper, the focus is on the improvement of accuracy for the horizontal components of the airborne gravity vector. This is achieved by using a decoupled model in the wave estimator and decorrelating the gravity disturbance from the INS system errors through the estimation process. The results of this method on the real strapdown INS/DGPS data are promising. The internal accuracy of the horizontal components of the estimated gravity disturbance for repeated airborne lines is comparable with the accuracy of the down component and is about 4–8 mGal. Better accuracy (2–4 mGal) is achieved after applying a wave-number correlation filter (WCF) to the parallel lines of the estimated airborne gravity disturbances.     

利用空中平均重力异常确定区域大地水准面

提出了直接利用空中平均重力异常计算区域大地水准面的方法。模拟计算的结果表明, 该方法与传统的利用地面平均空间重力异常确定的大地水准面精度相当, 但其显著优点是勿需空中重力异常的向下解析延拓, 从而可以避免延拓误差对大地水准面精化的影响。     

航空重力向下延拓的最小二乘配置Tikhonov正则化法

基于最小二乘配置法向下延拓航空重力的过程中,由于协方差矩阵严重病态,影响延拓结果的稳定性和精度。针对这一问题,提出了航空重力向下延拓的最小二乘配置Tikhonov正则化法。基于全球协方差函数模型建立航空重力数据与地面重力数据的协方差关系,引入基于广义交叉验证法,选择正则化参数的Tikhonov正则化法改善协方差矩阵的病态性,抑制观测噪声对延拓结果的放大影响。基于EGM2008重力场模型,设计了山区、丘陵和海域3种不同地形区域的航空重力数据向下延拓的仿真实验,实验结果验证了该方法的有效性。