Dem Generation from High Resolution Satellite Imagery Using Parallel Projection Model

DEM generation from stereoscopic imagery is contingent on establishing the mathematical model relating the scene coordinates of conjugate points to the ground coordinates of the corresponding object point. Either rigorous or approximate models can be used to establish such a relationship. Rigorous modelling necessitates a full understanding of the imaging geometry associated with the involved sensor. Moreover, it involves the external characteristics (as represented by the Exterior Orientation Parameters – EOP) and the internal characteristics (as represented by the Interior Orientation Parameters – IOP) of the imaging sensor. Such characteristics are derived with the help of control information, which might take the form of a calibration test field, ground control points, and/or onboard navigation units (e.g., GPS/INS). However, the derivation of these parameters might not be always possible due to: the lack of sufficient control; weak imaging geometry (especially for satellite imaging systems with narrow angular field of view); and/or intentional concealment by the data provider (e.g., Space Imaging does not release the IOP and the EOP for their commercially available imagery). Therefore, there has been an increasing interest to investigate approximate models, which do not explicitly involve the internal and external characteristics of the imaging system. Among them, parallel projection has become a popular model for its simplicity and accurate representation of imaging sensors with narrow angular field of view, which is the case for newly launched high resolution satellite imagery (e.g., IKONOS, QUICKBIRD, SPOT-5, ORBVIEW, and EOS-1). This paper presents a complete methodology for DEM generation from stereo-satellite scenes using parallel projection modelling of the imaging geometry. The performance of the developed methodology is evaluated through real datasets captured by SPOT-1, SPOT-2, and SPOT-5.