Photogrammetry on Turtle Mountain

What is Photogrammetry?

Photogrammetry uses repeat sets of low-level aerial photographs to monitor specific points on the ground. To monitor ground movement, we take several photographs at different times, and by comparing these images, we can measure how much each target has moved horizontally and vertically.

Photogrammetry on Turtle Mountain

Photogrammetric target installed on Turtle Mountain in 1982 and repainted during summer 2005.
Click on image to enlarge.

In 1981, 24 artificial targets were installed on Turtle Mountain to give broad coverage around South Peak, including both points considered stable to the west and south, and areas considered more active to the north and on the east side of South Peak.

Results

Photogrammetric target layout at the south peak of Turtle Mountain. The vector plots show the total deformation on the targets between 1982 and 2005. The deformations on Target 20 are from 1984 to 2005. Click on image to enlarge.

To analyze the photogrammetry results, photo coordinates were compared from the 2005 images to the 1982 aerial photos. As shown below, movement rates between 1982 and 2005 show that changes of up to 88 mm occurred on the east side of South Peak, with movements ranging between 19 and 42 mm on the larger mass between South Peak and Crack 1. Dr. M. Chapman, Ryerson University, completed the analysis.

These rates correspond to average, annual deformations of 0.9-3.2 mm over 23 years. When compared to results from other historical and recently installed monitoring points, we believe the overall movement rate is reasonable and provides the best picture of the movement patterns in the South Peak area.