GEOMETRIC CONSISTENCY AND STABILITY OF CONSUMER-GRADE DIGITAL CAMERAS FOR ACCURATE SPATIAL MEASUREMENT

摘要

It is known that uncertain internal geometry of consumer-grade digital cameras limits the accuracy of data that can be extracted. These cameras can be calibrated, but the validity of calibration data over a period of time should be carefully assessed before subsequent photogrammetric measurement. This paper examines the geometric stability and manufacturing consistency of a typical low-cost digital camera (Nikon Coolpix 5400) by estimating the degree of similarity between interior orientation parameters (IOP), established over a 1-year period. Digital elevation models (DEMs) were extracted with differing IOP, and accuracies were compared using data obtained from seven identical cameras. An independent self calibrating bundle adjustment (GAP) and the Leica Photogrammetry Suite (LPS) software were used to provide these data-sets. Results are presented that indicate the potential of these cameras to maintain their internal geometry in terms of temporal stability and manufacturing consistency. This study also identifies residual systematic error surfaces or "domes", discernible in "DEMs of difference". These are caused by slightly inaccurately estimated lens distortion parameters, which effectively constrain the accuracies achievable with this class of sensor.