MS.05 EnhancedDeformationAlgorithm

The use of the Enhanced

Deformation Algorithm when

hard rock and loose materials

are in the scan area

By Albert Cabrejo Senior Geotechnical Engineer

Commercial in Confidence

Overview

Slide 2

The Enhanced Deformation Algorithm (EDA) is

in the process of deployment in the SSR fleet

across the world.

The behaviour of the EDA in the external world

is still a matter of study, analysis and

calibration.

Education to the GP staff and external

customers is required in order to maximize the

use of this new feature of the SSRViewer

while keeping the information as reliable as

possible.The use of the Enhanced Deformation Algorithm when

hard rock and loose materials are in the scan area


Objectives

Show the performance on the real environment of the EDA.

Teach the GP staff and customers how to distinguish the behaviour

of the EDA from the previous algorithms.

Understand the consequences in the deformation images of

replacing scans (deformation plots are not available in the software

yet).

Illustrate a case in which the use of the EDA requires refinement in

terms of masks in order to achieve high quality monitoring by

avoiding the replacement of scans that should not be replaced.

Provide recommendations for the correct use of the EDA.

Slide 3

The use of the Enhanced Deformation Algorithm when



Enhanced Deformation

Algorithm How does it

work?

Slide 4




How does it work?

The EDA evaluates the scan area for ambiguous pixels, those who,

to sit a case, use to appear as purple pixels surrounded by red

pixels.

If a number of ambiguous pixels is found matching certain

parameters the scan is declared ambiguous.

An average of the deformations in the 5 previous scans is made and

the result is assigned as the deformation value that the user sees in

the SSRViewer.

The replacement of the scan is done for all the pixels in the scan

area so no individual pixels are replaced. This means that if a region

in the scan area is ambiguous the consequences will affect the rest

of the scan area, which might not be ambiguous.

The SSRViewer creates the image of Enhanced Deformation and

the images of Standard Deformation

Slide 5




Example of a scan that has been replaced

Slide 6

Enhanced Deformation Image

Standard Deformation Image




Which pixels are declared ambiguous?

Pixels that have an ambiguous step, positive or negative that define

a clear boundary from positive deformations to negative

deformations in large areas of the scan.

Pixels that are not masked out by the Enhanced Deformation Mask

Pixels with low coherence.

Pixels with low amplitude.

Pixels that didnt suffer an ambiguous step large enough to become

suspicious of being the consequence of a rapid atmospheric change.

Pixels that have been declared in the previous scan.

Pixels that have been declared ambiguous twice in the last 10 scans.

Slide 7




This scan was not replaced (low coherence)

Slide 8

Strong

boundary

from red

to purple

Low coherence in the pixels

with the deformation ambiguity

Zero scans have been replaced

(not red squares in the chart)




This scan was not replaced (few amb. pixels)

Slide 9

Boundary

too small

High coherence at the scan

selected.

One scan was replaced, but not

in the scan selected (blue line)




This scan was replaced: all criteria reached

Slide 10

Long and well

defined boundary

High coherence at the scan

selected.

The scan selected (blue line)

shows a red square: it has been

replaced by the EDA.

The EDA image

is different than

the SDA image

as

consequence of

the replacement




Long term consequence

of replacing scans

Slide 11




The consequence in loose materials might be

negligible (large deformations involved)

Slide 12

The differences in deformations between the two algorithms might not be so

important, since the magnitude of deformations is several times larger than the

possible artefact introduced by each replaced scan.

Hard materials at the top

Standard Deformation Image400mm

Loose materials at the bottom




The consequence in loose materials might be

negligible (large deformations involved)

Slide 13

The differences in deformations between the two algorithms might not be so

important, since the magnitude of deformations is several times larger than the

possible artefact introduced by each replaced scan.



400mm

400mm




The consequence in hard materials might be significant

Slide 14

The small positive and negative deformations indicated by the deformation image

might be significant in terms of alarming for brittle failures.

Enhanced Deformation Image 5mm

Continuous replacement of scans due to ambiguities in the loose materials

might hide the rapid development of collapses in the hard materials in the scan

area.




The consequence in hard materials might be significant

Slide 15

The small positive and negative deformations indicated by the deformation image

might be significant in terms of alarming for brittle failures.



5mm

5mm

Larger deformations reported

by the SDA compared to the

EDA in these pixels?




Example of missing positive deformations

Slide 16

Replacing scans might keep the user from detecting rapid developing deformations

leading to brittle failure.

2mm

2mm



Where did these

deformations go

with the EDA?

measured with the SDA

Positive deformation

measured with the SDA




Optimization of the

Enhanced Deformation

Algorithm Application

Slide 17



Commercial in ConfidenceSlide 18

How to use the Enhanced Deformation Algorithm Correctly?

The example presented in the previous slide represents a situation in which the

Enhanced Deformation Mask needs to be applied.

In rare situations this mask is required and we are

starting to learn which are the possible situations in

which it should be used.

The site presented before is Andina, where a high

wall is being scanned along with active dumps that

are deforming at large rates, triggering ambiguities.

Normally, when the dumps are active they will have low coherence due to the

constant change in the superficial appearance of the rocks. However, there

might be periods of no dumping in and high deformation rates without large

changes in the surficial appearance of the materials (high coherence). In

consequence, the dump might be a valid area for evaluation of the Ambiguous

Scan, which could lead to problems of unintended scan replacements.The use of the Enhanced Deformation Algorithm when



How to use the EDA Correctly? (cont)

To keep the loose materials from being investigated for ambiguities it is

required to apply the Enhanced Deformation Mask over them.

The use of a normal mask will keep the user from monitoring the

dumps, so it is not an option.

The use of the alarms mask is not related to the EDA evaluation

process.

If no mask is applied, several scans might be replaced due to fast

deformations on the dumps rather than being applied only under

extreme atmospheric conditions, which is the goal of this algorithm.




How to use the EDA Correctly? (cont)

Applying the Enhanced Deformation Mask will prevent the replacement

of scans that should not be replaced due to the important deformation

measurements that might be in development in the hard materials. A

suggested Enhanced Deformation Mask is presented in the image

below.




Brown Alerts

06:07, Mon 12 Dec, 2011 brown alert

Wall directory is

d:\ssr\SSR108_111211_Andina_MinaSurSur_Botadero2

Computer's SSR label is: 192.168.1.2

The recommended optimal limit of 5 consecutive scans has been

exceeded.

Seek Geotechnical support for review of your radar scan setup.

Push the 'Delay for 15 minutes' button to suppress this grey alert for

15 minutes to undertake analysis of the enhanced deformation data.

If number of 5 scans are replaced consecutively, the result of the

deformation measurements is the average of previous averages, rather

than a real measurement of the displacement of the wall. This is not

adequate and could lead to wrong decisions due to the lack of real data.

The brown alerts were introduced in order to provide warning on this

situation happening so the issue can be addressed. For further

information consult the SSRViewer Suite 5.4 User Manual.




Conclusion

The Enhanced Deformation Algorithm is a powerful tool that GroundProbe

has developed in order to achieve higher data quality than ever before.

This algorithm is the preferred selection when defining the atmospheric

correction algorithm in the vast majority of cases. The older algorithms are

to be used only under specific direction by GroundProbe, in special cases.

From the case study presented here we are learning that when dumps are

in the same scan area than hard rock the Enhanced Deformation Mask

needs to be applied.

The inappropriate use of the EDA could lead to:

Unintended replacement of scans

Lack of deformation data in areas that are susceptible of brittle failure

Constant grey alerts.

If SMS and e-mail procedures are defined, the users will receive

meaningless notifications.The use of the Enhanced Deformation Algorithm when


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MS.05 EnhancedDeformationAlgorithm