Detection of millimetric deformation using a terrestrial laser scanner: experiment and application to a rockfall event

Abstract. Terrestrial laser scanning (TLS) is one of the most promising surveying techniques for rockslope characteriza- tion and monitoring. Landslide and rockfall movements can be detected by means of comparison of sequential scans. One of the most pressing challenges of natural hazards is com- bined temporal and spatial prediction of rockfall. An outdoor experiment was performed to ascertain whether the TLS in- strumental error is small enough to enable detection of pre- cursory displacements of millimetric magnitude. This con- sists of a known displacement of three objects relative to a stable surface. Results show that millimetric changes cannot be detected by the analysis of the unprocessed datasets. Dis- placement measurement are improved considerably by ap- plying Nearest Neighbour (NN) averaging, which reduces the error (1σ ) up to a factor of 6. This technique was ap- plied to displacements prior to the April 2007 rockfall event at Castellfollit de la Roca, Spain. The maximum precursory displacement measured was 45 mm, approximately 2.5 times the standard deviation of the model comparison, hampering the distinction between actual displacement and instrumen- tal error using conventional methodologies. Encouragingly, the precursory displacement was clearly detected by apply- ing the NN averaging method. These results show that mil- limetric displacements prior to failure can be detected using TLS.

VIP Connection Newsletter, August 2001, Vol. 1, no. 4

Iowa Lottery Authority Player Information Newsletter

VIP Connection Newsletter, December 2001, Vol. 1, no. 5

Iowa Lottery Authority Player Information Newsletter

VIP Connection Newsletter, July 2002, Vol. 2, no. 2

Iowa Lottery Authority Player Information Newsletter

Lottery Action, July 8-21, 2002, Vol. 9 no. 13

Iowa Lottery Authority Retailer Information Newsletter

Lottery Action, July 22-August 4, 2002, Vol. 9 no. 14

Iowa Lottery Authority Retailer Information Newsletter

Lottery Action, August 5-18 2002, Vol.9, no.15,

Newsletter for Iowa Lottrey

Lottery Action, August 19-September 8, 2002 Vol. 9, no. 16

Iowa Lottery Authority Retailer Information Newsletter

Lottery Action, September 9-22, 2002 Vol. 9, no. 17

Iowa Lottery Authority Retailer Information Newsletter

Lottery Action, September 23-October 6, 2002, Vol. 9, no. 18

Newsletter for Iowa Lottery

Lottery Action, October 7-20, 2002 Vol. 9 no. 19

Newsletter for Iowa Lottery

Lottery Action, October 21-November 3, 2002, Vol. 9, no. 20

Newsletter for Iowa Lottery

VIP Connection Newsletter, October 2002, Vol. 2, no. 3

Iowa Lottery Authority Player Information Newsletter

Lottery Action, November 4-17, 2002, Vol. 9, no. 21

Newsletter for Iowa Lottery

Lottery Action, November 18-December 1, 2002, Vol. 9 no. 22

Newsletter for Iowa Lottery