1、附录 1：英文原文 ISPRS Journal of Photogrammetry and Remote Sensing YUAN 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 Abstract In traditional GPS-supported aero triangulation, differential GPS (DGPS) positioning tech
2、nology 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 posit
3、ioning 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 p
4、hotography. 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
5、of actual 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
6、 at a scale 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 triangu
7、lation 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. H
8、owever, 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 e
9、ach strip, 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,
10、it can 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； s
11、ingle epoch GPS positioning； ambiguity resolution Introduction Aerial 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
12、 commonly 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
13、 themany 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 appli
14、ed in 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 o
15、f perspective 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 extensiv
16、ely 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 Navigatio
17、n System(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 PO
18、S (Cannon 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
19、block 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 m
20、ore 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
21、 surveying 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, atmospheric 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
