【正文】 fied points obtained from standard AT and GPSsupport AT both satisfied the requirement of 4D product, and that the accuracy of exterior orientation elements obtained by these two methods are generally similar. The larger the photo scale is, the higher the accuracy of the photo’s linear elements we can get。 Remote Sensing, 51(2): 99108 [5] Cramer M, Stallmann D, Haala N (2020) Direct georeferencing using GPS/Inertial exterior orientations for photogrammetric applications [C]. International Archives of Photogrammetry and Remote Sensing, 33(B3): 198205 [6] Gruen A, Baer S (2020) Aerial mobile mapping georeferencing without GPS/INS [C]. The 3rd International Symposium on Mobile Mapping Technology, Cairo [7] Jacobsen K (2020) Calibration aspects in direct georeferencing of frame imagery [C]. Pecora 15/Land Satellite Information, ISPRS Commission I/IV [8] Mostafa M R (2020) Camera/IMU boresight calibration: new advances and performance analysis [C].The ASPRS Annual Meeting, Washington . [9] Yuan Xiuxiao, Xie Chou, Wang Shugen (2020) Image orientation by bined bundle adjustment with fixed imageries [J]. International Archives for Photogrammetry and Remote Sensing, 35(B2):3438 [10] Applanix Product Outline [OL]. /products/ [11] State Bureau of Standard (1998) 1:500, 1:1 000, 1:2 000 Topographic maps specifications for aerophotogrammetric office operation [S]. Beijing: Standards Press of China (in Chinese) [12] State Bureau of Technology Supervision (1993) 1:5 000, 1:10 000 topographic maps specifications for aerophotogrammetric office operation [S]. Beijing: Standards Press of China (in Chinese) [13] State Bureau of Technology Supervision (1991) 1:25 000, 1:50 000, 1:100 000 topographic maps specifications for aerophotogrammetric office operation [S]. Beijing: Standards Press of China (in Chinese) [14] Wang Zhizhuo (1990) Principle of photogrammetry (with remote sensing) [M]. Wuhan: Press of Wuhan University of Surveying and Mapping。 for difficult areas, noncharted areas or areas that are not accessible, GPSsupport AT without GCPs can be adopted to acquire the basic spatial information for producing national base maps。 =Δ∑ 。 GPS (global positioning system)。 State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, 129 Luoyu Road,Wuhan 430079, China. Email： Geospatial Information Science 11(4): 235242 236 production costs, triggering the revolution in the field of photogrammetry[2]. Nevertheless, GPSsupported AT is advantageous for aerial photogrammetric operation primarily over vast and difficult areas, at small and medium mapping scales, not for striplike zone and urban largescale mapping[3]. In the 1990s, people started to investigate employing GPS/INS integrated system (also called POS) to acquire a photo’s position and attitude (., to obtain exposure station’s position by GPS, and images’ attitude elements by IMU), for the purpose of photo orientation, and the final goal is to replace block aero triangulation procedure[49]. Modern digital photogrammetry will play an important role in automated productions of 4D products (DEM, DOM, DLG, DRG) and updating of spatial databases. This paper will introduce current operational applications of aerial photogrammetry and related technical requirements, in particular, geometric positioning accuracy obtainable in the photogrammetric information chain from photo orientation to stereomodel reconstitution, aiming to investigate their practicability for 4D products production. It is hoped that findings from this study will provide guidance for operational aerial photogrammetry in the context of national land surveying, mapping, and fundamental geographic information acquisition. 1 Current patterns of the modern aerial photogrammetry Nowadays, there are primarily three patterns for aerial photogrammetry, namely, standard aerial photogrammetry, GPSsupported aerial photogrammetry and POSsupported aerial photogrammetry. Their main procedures are shown as . Flowchart of the modern aerial photogrammetryFrom , we can learn that the main difference between these three patterns lies in the ways of aerial photo acquisition and photo orientation. For standard AT, it is through block aerotriangulation with a large number of GCPs to get a model orientation points’ coordinates to plete image orientation. For GPSsupported AT, in aerial photo acquisition process, dynamic GPS positioning is used instead of GCPs to determine the positions of exposure center and meanwhile obtain the model’s orientation points’ coordinates, which are then used to rectify the image’s orientation. For POSsupported AT, images and their corresponding orientation elements (six exterior orientation elements of images) are both acquired, in order to realize geometric inversion of photography by storing their spatial positions and attitude at the moment of exposure. 2 Related technologic requirements Aerial photography In modern aerial photography, in order to improve the quality of obtained images, besides adding flight control systems to aerial camera (such as ASCOT, CCNS4, Aerial TRACKER system), the methods in