外文翻译---GPS的精密单点定位技术在空中三角测量的应用

1、.附录1：英文原文ISPRS Journal of Photogrammetry and Remote SensingYUAN Xiu-xiao(袁绣萧)FU Jan-hong(福剑虹)SUN Hong-xing( 孙红星)The application of GPS precise point positioning technology in aerial triangulation AbstractIn traditional GPS-supported aero triangulation, differential GPS (DGPS) positioning technology

2、is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs).However, the establishment of GPS reference stations for DGPS positioning

3、is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photogra

4、phy. Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actu

5、al aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a s

6、cale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation

7、can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail.The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However,

8、 if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each str

9、ip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can

10、still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales. ' 2009 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.Key words: deformation monitoring; landslide; sin

11、gle epoch GPS positioning; ambiguity resolutionIntroductionAerial triangulation (AT) is the basicmethod for analyzing aerial images in order to calculate the 3-dimensional coordinates of object points and the exterior orientation elements of images. Up until now, bundle block adjustment has been com

12、monly employed for AT, and numerous ground control points (GCPs) are necessary for the adjustment computation (Wang, 1990). In the 1950s, photogrammetrists began exploiting other auxiliary data to reduce the number of GCPs. However, investigation did not achieve an implementing result because of the

13、many technological limitations at that time (Li and Shan, 1989). In the 1970s, with the application of Global Positioning System (GPS), the situation changed a lot. GPS can provide 3-dimensional coordinates of surveying points with centimeter accuracy in differential mode, it was therefore applied i

14、n AT to measure the spatial position coordinates of the projection centers (referred to as GPS camera stations or airborne GPS control points). In this way, the number of GCPs could be significantly reduced. Block adjustment of combined photogrammetric observations and GPS-determined positions of pe

15、rspective centers is regarded as GPS-supported AT. Since the beginning of the 1980s, many papers have presented the significant research and experimental results of GPS-supported AT (Ackermann, 1984; Friess, 1986; Lucas, 1987). After about 20 years of these efforts, GPS-supported AT was extensively

16、applied in aerial triangulation at many scales and in all types of terrain. It is particularly beneficial in areas where they are difficult to establish ground control (Ackermann, 1994). In the late 1990s, with the development of sensor technology, an integrated systemof GPS / Inertial Navigation Sy

17、stem(POS)was first used in AT to obtain the position and attitude information of aerial images directly. This technology, in theory, can eliminate the need for GCPs. However, research indicates that the digital orthophoto map can be made directly by image orientation parameters obtained via a POS (C

18、annon and Sun, 1996; Cramer et al., 2000; Heipke et al., 2001), but there will be larger vertical parallax when stereo models are reconstructed using these image orientation parameters and the height accuracy cannot satisfy the requirement of large scale topographic mapping. Therefore, a bundle bloc

19、k adjustment should be made, combined image orientation parameters obtained via the POS and photogrammetric observations (Greening et al., 2000). Whether exploiting GPS data or POS data in AT, DGPS positioning is necessary to provide the GPS camera stations at present. In the DGPS mode, one or more

20、GPS reference stations should be emplaced on the ground and observed synchronously and continuously together with the airborne GPS receiver during the entire flight mission. Additionally, signals from GPS satellites should be received as few transmission interruptions as possible. Initialization sur

21、veying is also required before aircraft takes off and static surveying should be performed after landing. In the processing of GPS observations, carrier phase differential technique is used to eliminate or reduce GPS positioning errors, including satellite clock error, satellite orbit error, atmosph

22、eric delay error, and so on. Generally speaking, it is difficult to emplace proper GPS reference stations when the aerial photographic region is with large scope or difficult to access and communicate. In order to guarantee the quality of aerial images, a survey area must be photographed for a long

23、period, which is result from the shortage of weather suitable for photography. GPS reference stations must therefore remain in place for a long time. Moreover, the accuracy of DGPS positioning is relevant to the length of baseline. The longer the baseline, the weaker the correlation between ionosphe

24、ric refraction error and tropospheric delay error. Due to the need for spatial correlation of atmospheric delay errors, the lengths of GPS differential baselines are typically limited to within 20 km if centimeter level accuracy is required with high reliability (Sun, 2004). When it comes to aerial

25、photogrammetry, this is difficult because the length of survey areas is typically more than 200 km and the distance between the survey area and the airport may be greater. For baselines with long length, the atmospheric delay mainly composed of ionospheric delay and tropospheric delay will degrade p

26、ositioning accuracy significantly. In such cases, even the ionospheric delay can be almost removed by using dual frequency GPS receivers. However, there can still be a tropospheric delay within a few decimeters, meaning that for long baselines, the positioning accuracy is typically in the level of d

27、ecimeters. At the same time, the establishment of GPS reference stations sometimes makes the implementation of a survey plan difficult due to traffic, communication and cost considerations. As a result, the method of replacing GPS reference stations by Continuous Operating Reference Stations (CORS)

28、was proposed and obtained an accuracy in decimeter level compared with the results obtained by GPS reference stations (Bruton et al., 2001;Mostafa and Hutton, 2001). There are, however, no CORS in most of the survey areas, so this method cannot be applied extensively. With the development of GPS tec

29、hnology, the number of CORS is increasing all over the world and their distribution is more and more reasonable. International GNSS Service (IGS) can provide precise satellite orbit and clock error products with accuracies of 5 cm and 0.1 ns (3 cm). Utilizing IGS products, if the atmospheric delay e

30、rror can be removed, modeled or estimated at the centimeter level, it will be possible to obtain centimeter level positioning accuracy with only the observation of a single GPS receiver. Zumberge et al. presented a GPS precise point positioning (PPP) method based on an un-differenced mode and achiev

31、ed centimeter level accuracy for static positioning (Zumberge et al., 1997, 1998). Later, Muellerchoen et al. presented a method for realizing GPS global precise real time kinematic positioning by using single epoch un-differenced dual frequency observations after initialization (Muellerchoen et al.

32、, 2000). In this way, centimeter to decimeter level accuracy can be achieved for aerial GPS kinematic positioning at present (Gao and Chen, 2004; Zhang et al., 2006). If GPS PPP technology is applied in GPS-supported AT, only one GPS receiver is mounted on the aircraft and GPS reference stations on

33、the ground are no longer required. GPS-supported AT can therefore be implemented very easily andwith great flexibility, which is obviously significant in large survey blocks or areas with difficult terrain. Therefore, GPS PPP technology is discussed in this paper based on the highly dynamic characte

34、ristic of aerial remote sensing. The error law of GPS camera stations obtained by this method is analyzed, and the positioning accuracy and the feasibility of GPS-supported AT using GPS PPP technology are discussed. The goal of this work is to eliminate the need for the GPS reference stations in GPS

35、-supported aerial photography by the GPS PPP technology. This technology can not only reduce the cost of aerial photography but also increase the flexibility of aerial photographic operations,which is beneficial to thewidespread use of GPS-supported AT. 2. GPS precise point positioning for aerial tr

36、iangulation In contrast to DGPS positioning technology, GPS PPP is a type of absolute GPS positioning which uses IGS precise orbit parameters and clock error products. The main algorithms and correction models for the GPS PPP have been discussed in many papers (Han et al., 2001; Kouba and Heroux, 20

37、01; Holfmann et al., 2003; Chen et al., 2004) and the most widely used data type is un-differenced ionosphere-free carrier phase measurements, or an ionosphere- free combination with carrier phase and code pseudorange measurements. An alternative data type used by some studies is code-phase ionosphe

38、re-free combination that aims at accelerating the convergence speed for parameter solutions (Gao and Chen, 2004). In this paper, the single difference model is employed for reasons that will be discussed below. For simplification, error corrections including relativity, satellite phase center offset

39、, satellite wind up, earth body tide, ocean load correction and so on, will not be discussed here. The original un-differenced data type is formed by an ionosphere-free combination of dual frequency GPS data (Kouba and Heroux, 2001): (A-1)Here, j denotes satellite; Q j is the ionosphere-free combina

40、tion of L1 and L2 code pseudorange; j is the geocentric distance from the GPS receiver to the satellite j; dt is the GPS receiver clock error; dt j is the clock error of the satellite j, which can be obtained from IGS products; c is the vacuum speed of light; T is the zenith tropospheric delay; Mj i

41、s the mapping function of tropospheric delay for satellite j, for which several models can be used; j is the ionosphere-free combination of L1 and L2 carrier phase; Nj is the non-integer ambiguity of ionosphere-free carrier phase combination; "Q and "are the noises. There are five unknown

42、parameters in Eq. (1), including the 3-dimensional spatial coordinates of the receiver (X; Y; Z) lying in j , the zenith tropospheric delay T and the receiver clock error dt. Furthermore, in Eq. (2), besides the same parameters in Eq. (1), the ambiguity Nj is unknown. For these unknown parameters, t

43、he ambiguity Nj is constant if the cycle slip is repaired and the zenith tropospheric delay T changes very slowly or remains unchanged over a short time span, for example, over two hours. The receiver clock error dt changes very quickly and the coordinates of the receiver (X; Y; Z) are dependent on

44、the vehicle movement status. In aerial photogrammetric applications, the craft often carries out large maneuvers, the sequential filter based on the dynamic models of all parameters (Kouba and Heroux, 2001) can not be implemented for high accurate positioning because the process noises of the vehicl

45、e movement and the receiver clock error are very large. In this case, the recursive least squares algorithm can be used to separate the receiver coordinate and clock error from other parameters which remain constant or change very slowly (Chen et al., 2004). Assuming that X and Y are the two kinds o

46、f parameters to be estimated, the observation equation in matrix Form can be written as : (A-2) where L is observation vector; X is correction vector of the coordinates of GPS receiver antenna phase center and clock error; Y is vector of ambiguity parameters and the correction parameters to zenith t

47、ropospheric delay; A and B are design matrices; " is the noise vector; 0 is the standard deviation of the noise; P is the weight matrix of observations. 附录2：中文翻译GPS的精密单点定位技术在空中三角测量的应用袁绣萧 福剑虹 孙红星摘 要 在传统的GPS辅助空中三角测量,差分全球定位系统（DGPS）定位技术用于确定曝光时间透视中心的3维坐标厘米到分米级精度。这种方法可以大大减少地面控制点控制点的数量。但是DGPS定位的GPS基准站

48、的建立不仅劳动密集和昂贵的但同时也增加了航拍的实施难度。本文建议空中三角GPS精密单点定位的方式以避免使用的GPS基准站和简化的航拍工作PPP的支持。首先我们提出了在空中三角测量应用中的GPS的单点定位技术算法。其次使用GPS的PPP确定的角度中心的坐标错误的法律进行了分析。第三四套测绘项目的实际空中拍摄的图像不同的地形和摄影的比例基于GPS的单点定位技术和由作者自行研制的空中三角测量软件给出了实验模型。平坦地区为1:2500 的比例一个多山的地区为1:3000的比例在高山区和高地地区比例分别为1:32000和1:60000。在这些实验中GPS的PPP结果进行比较结果获得通过DGPS定位和传统

49、的平差。在这样的GPS的单点定位技术的实证定位在空中三角测量精度可以估算的。最后从GPS的单点定位技术的机载GPS控制的平差结果进行了详细分析。实证结果表明PPP的GPS空中三角测量应用有一个半米高的水平和几个分米内的随机误差的系统误差。然而如果采用了适当的调整解决方案系统误差可以消除GPS平差。当四个完整的地面控制点布设在调整块角落然后系统误差补偿各带一组独立的未知参数机载全球定位系统GPS的控制的平差最终的结果是购买廉价的机载的数据精度和GPS差分全球定位系统精度相同。虽然前者的精度比传统束密集的地面控制点区域网平差低一点它仍然可以在许多尺度地形测绘满足摄影点测定的精度要求。 关键词形变监

50、测滑坡GPS单历元定位模糊度解算绪论 空中三角测量（AT）是用于分析天线的基本方法为了计算3维坐标的图像对象点和影像的外方位元素。到现在为止已普遍采用平差AT和大量的地面控制点控制点是必要的调整计算。在20世纪50年代摄影测量开始利用其他辅助数据以减少控制点的数量。然而当时调查并没有达到因为技术限制许多实施结果（李和山，1989） 在20世纪70年代随着应用全球定位系统（GPS）况发生了很大变化。GPS可提供测点的三维坐标厘米级精度在差分模式，因此它是适用于AT来衡量的空间位置坐标投影中心（以下简称来GPS相机站或作为机载GPS控制点）在这种方式控制点的数量可显着降低。联合平差摄影观测和全球卫

51、星定位系统确定位置透视中心被认为是作为GPS的支持。自从20世纪80年代开始，许多论文已提交的大量的研究和实验结果的GPS支持（阿克曼，1984；弗里斯1986；卢卡斯，1987 ）。经过约20年这些努力， GPS的支持，广泛应用于空中三角测量在许多尺度和所有类型的地形。这是特别有利的地方，他们是难以建立地面控制(阿克曼 1994)。 在20世纪90年代后期，随着传感器技术的发展，GPS 惯性导航系统( POS) 第一次使用在AT直接航拍图像获得的立体像对和地形的信息。在理论上,这种技术可以消除为控制点的需要。然而研究表明,数字正射影像图可直接由地面点定位坐标;通过一台POS(Cannon和s

52、un, 1996年获得的参数等人2000年, Heipke等,2001 )但将有较大的垂直视差立体模型重建时使用这些图像定向参数和高程精度不能满足大比例尺地形图测绘的要求。因此束块应作出调整合并后的图像通过POS和摄影获得的定向参数意见(Greening等2000) 。 是否利用POS机在AT 差分全球定位系统GPS数据或数据定位是提供必要的GPS相机站呈现。在差分全球定位系统模式下一个或多个GPS基准站应布设在地面上,并同步观察期间不断连同机载GPS接收机整个飞行任务。此外,从GPS卫星信号应收到尽可能少的传输中断。还需要之前飞机起飞和初始化测量着陆后静态测量应当执行。 在处理GPS观测载波相位差技术被用来消除或减少GPS定位误差,包括卫星时钟误差,卫星轨道误差,大气延迟误差等。一般来说它是很难放列正确的GPS参考站时航空摄影区域与大范围或难以进行访问和交流。为了航拍图像以保证质量,调查面积必须等很长一段时间拍摄,这是为了适合天气来摄影。 GPS基准站因此很长一段时间留在原地。此外准确性还和DGPS定位基线长度有关。时间越长基线之间电离层的相关性较弱折射误差,对流层延迟误差越小。由于需要大气延迟误差,长度的空间相关性GPS差分基准通常限制在20公里内.如果厘米级精度要求高可靠性(星期日200