Hybrid Measurement Scenarios in Automated Close-range Photogrammetry

Automated close-range photogrammetric measurement has traditionally been associated with expensive specialist cameras and usually requires highly controlled image illumination conditions. In the past few years, however, there has been a significant amount of research into the development of automated routines and algorithms that support the employment of consumer-grade colour digital cameras for everyday photogrammetric measurement tasks. These include, but are not limited to, fully automatic network orientation, image point correspondence determination and camera calibration. This paper discusses the further requirement of a hybrid-measurement approach, where automatic orientation routines are supported, as well as follow-up manual and semi-automatic operations such as natural feature point extraction, manual point measurement and operator-assisted surface definition via image matching. Control over image illumination is not critical; however the use of retro-reflective targeting ensures a high level of process automation prior to the manual phase of hybrid measurement. Topics discussed include the exploitation of colour from imagery and targeting, issues regarding automatic network orientation and image point correspondence determination in normally exposed imagery, operator-assisted surface extraction, and a special condition placed on the bundle adjustment to support both automatic and manual image measurements.