Spatial accuracy of orthorectified IKONOS imagery and historical aerial photographs across five sites in China

Abstract

High‐resolution (⩽1 m) satellite imagery and archival World War II era (WW2) aerial photographs are currently available to support high‐resolution long‐term change measurements at sites across China. A major limitation to these measurements is the spatial accuracy with which this imagery can be orthorectified and co‐registered. We orthorectified IKONOS 1 m resolution GEO‐format imagery and WW2 aerial photographs across five 100 km² rural sites in China with terrain ranging from flat to hilly to mountainous. Ground control points (GCPs) were collected uniformly across 100 km² IKONOS scenes using a differential Global Positioning Systems (GPS) field campaign. WW2 aerial photos were co‐registered to orthorectified IKONOS imagery using bundle block adjustment and rational function models. GCP precision, terrain relief and the number and distribution of GCPs significantly influenced image orthorectification accuracy. Root mean square errors (RMSEs) at GCPs for IKONOS imagery were <2.0 m (0.9–2.0 m) for all sites except the most heterogeneous site (Sichuan Province, 2.6 m), meeting 1:12 000 to 1:4800 US National Map Accuracy Standards and equalling IKONOS Precision and Pro format accuracy standards. RMSEs for WW2 aerial photos ranged from 0.2 to 3.5 m at GCPs and from 4.4 to 6.2 m at independent checkpoints (ICPs), meeting minimum requirements for high‐resolution change detection.

Acknowledgements

This material is based upon work supported by the US National Science Foundation under Grant DEB‐0075617 awarded to Erle C. Ellis in 2000, conducted in collaboration with Prof. Linzhang Yang of the Institute of Soil Science, Chinese Academy of Sciences (CAS), Nanjing, China, Prof. Hua Ouyang of the Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, China and Prof. Xu Cheng of China Agricultural University, Beijing, China. We are grateful to Kui Peng, Hongsheng Xiao, Shoucheng Li, Xinping Liu, Renzong Ruan and local collaborators and field assistants at the five sites for field investigation in China. We also thank Michael Leonard for help in locating aerial photos, Kevin Klingebiel for image scanning and initial registration, the National Archives and Records Administration (NARA) for providing WW2 aerial photographs (special thanks to Sam Welch of NARA) and Space Imaging Inc. for providing IKONOS imagery. We would also like to thank anonymous reviewers for helpful comments on the manuscript. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Notes

†Numbers of GCPs and ICPs did not include stereo GCPs and ICPs.

‡Using rational function (RF) model, other photos using bundle block adjustment method.