126
9 Hazard Identification
Radar reflections (Ulaby et al. 1986) are the result of the type of surface and the
geometry of the observation. For instance, flat calm water will redirect the radiation
away from the radar and an image will show low backscatter values. A metal roof,
oriented to reflect radiation toward the radar, is a very bright target while a ceramic
structure would be basically invisible to a radar. With the understanding of the reflective properties of the structures to be observed, the dependability of radar means that
it is possible to make series of observations over long periods of time that allow
the automated detection of changes from, for instance, construction, soil wetness or
standing water, and vegetation health issues relative to year-by-year changes.
Reproducible measurements of ground movement have been demonstrated to
within 2 mm/month (Henschel and Lehrbass 2011; Henschel et al. 2015; Mäkitaavola et al. 2016). As an example, the movement on a tailings dam over a period
of years is shown in Fig. 9.3. The graph demonstrates a small range of movement
over a long period of time. The accuracy of the InSAR and the consistency of radar
measurements make it possible to watch for the development of movement trends
altering previous risk estimates. The InSAR is particularly useful for the development
of baseline movement before storage or mining activities begin, i.e., at a prefeasibility
risk assessment level.
Tailings Storage Facility
Cumulative Horizontal (a) and Vertical (b) Deformation (m)
Time Series Plots - August 20, 2013 to June 17, 2016
(a)
(b)
© MDA Geospatial Services Inc. (2016) - All Rights Reserved.
© 2015 DigitalGlobe, Inc. - All Rights Reserved.
Deformation from -0.01 to 0.01 m
is displayed with 40% transparency.
-0.2
0.2
0.0
(m)
Lateral Movement
(easterly direction)
Subsidence
Fig. 9.3 Example of movement seen on a tailings dam by the long-term use of InSAR. The movement is shown both as a cumulative image and as a progression of the labelled square over time
9 Hazard Identification
Radar reflections (Ulaby et al. 1986) are the result of the type of surface and the
geometry of the observation. For instance, flat calm water will redirect the radiation
away from the radar and an image will show low backscatter values. A metal roof,
oriented to reflect radiation toward the radar, is a very bright target while a ceramic
structure would be basically invisible to a radar. With the understanding of the reflective properties of the structures to be observed, the dependability of radar means that
it is possible to make series of observations over long periods of time that allow
the automated detection of changes from, for instance, construction, soil wetness or
standing water, and vegetation health issues relative to year-by-year changes.
Reproducible measurements of ground movement have been demonstrated to
within 2 mm/month (Henschel and Lehrbass 2011; Henschel et al. 2015; Mäkitaavola et al. 2016). As an example, the movement on a tailings dam over a period
of years is shown in Fig. 9.3. The graph demonstrates a small range of movement
over a long period of time. The accuracy of the InSAR and the consistency of radar
measurements make it possible to watch for the development of movement trends
altering previous risk estimates. The InSAR is particularly useful for the development
of baseline movement before storage or mining activities begin, i.e., at a prefeasibility
risk assessment level.
Tailings Storage Facility
Cumulative Horizontal (a) and Vertical (b) Deformation (m)
Time Series Plots - August 20, 2013 to June 17, 2016
(a)
(b)
© MDA Geospatial Services Inc. (2016) - All Rights Reserved.
© 2015 DigitalGlobe, Inc. - All Rights Reserved.
Deformation from -0.01 to 0.01 m
is displayed with 40% transparency.
-0.2
0.2
0.0
(m)
Lateral Movement
(easterly direction)
Subsidence
Fig. 9.3 Example of movement seen on a tailings dam by the long-term use of InSAR. The movement is shown both as a cumulative image and as a progression of the labelled square over time