Slope failures and landslides associated with earthquakes and typhoons are major natural hazards in Taiwan's mountain highways. This paper attempts to apply photogrammetry technique to carry out speedy in-situ survey. We firstly create the three-dimensional (3D) model of a brick wall and validate that the average error is 0.28 mm in the measured distance. Afterward, the same measurement procedures are applied in an in-situ mudstone slope. The average error in the estimated distance is 0.41cm. Therefore, the investigating result guarantees the accuracy of applying Photogrammetry to investigate the geometry of in-situ failed slope.
In Taiwan's mountain areas, slope failures and landslides associated with earthquakes and typhoons are major natural hazards. The in-situ investigation must be proceeded to clarify a complicated combination of factors of slope failures caused by seismic force and rainfall (Oka, 1997). Methods for measuring the volume variation of the slope includes measuring object coordinates of targets, which is placed in danger location, using GPS observation networks, measurement with observation networks of high precision total station, and using 3D laser scanner to get the surface condition of a slope (Miura, Hattori, Akimoto and Nishiyama, 2004; Mikos, Vidmar and Brilly, 2005). However, these methods have not been widely used owing to their long measurement time or high cost. Photogrammetry is a visual metrology, and has been successfully applied in medical investigations, facial image identification, underwater surveying, and slope deformation monitoring (Mitchell, 1995; Green, Matthews and Turanli, 2002; Lynnerup, Adersen and Lauritsen, 2003; Miura, Hattori, Akimoto and Nishiyama, 2004). This paper uses Photogrammetry accompanying to a computer program, the Eos Systems program, PhotoModeler Pro 5, for speedy investigation and measuring the variation of a slope. The Nikon D100 digital camera with six million pixels is used. A laboratory experiment is conducted to a brick wall to insure the investigation procedures workable before an in-situ test.
