May 21, 2019
Sustainability and durability are strictly related to the monitoring of structures and the ability of the observer to deliver complete and efficient data for the object’s behaviour within time. Structural Health Monitoring is an inevitable part of geotechnical monitoring that ensures the regular health check-up of existing buildings, monuments, structures, dams, tunnels, etc.
Encardio Moniterra Group is all set to bring about a revolution in sustainable structural deformation monitoring with its unique software – OPSIS. Let’s have a look into this incredible application that would be the real game-changer in this field.
Figure 1: Laser Scanning Of A Tunnel
Laser Scanning is a technique that automatically monitors and collects the data in real-time with 3-dimensional surface coordinates of an object in a normal grid. It is considered as a rapid and reliable surveying method as it collects data in a static, stop and go or kinematic mode. The exported section profiles can be used to monitor deformations or displacements from the point where a cloud is produced.
A Laser Scanner is an instrument developed to determine displacements or deformations of a surface. Within minutes, it collects a dense point cloud getting a full detailed description of the monitored object.
Despite the fact that this method is fast, contactless and complete, scanning was not extensively used due to three reasons:
Cost of purchasing a laser scanner
The instrument’s specified accuracy
Handling of such a large amount of data.
However, from the last couple of years, laser scanners are accurate and affordable.
The terrestrial Laser Scanner or LiDAR has been used in the fields of surveying engineering and geomatics extensively as the evolution and improvements in its technology allowed the collection of increasingly more accurate data sets.
Despite the benefits of LiDAR over other data collecting methods, such as the remarkably higher amount of data collected for the same area in reduced periods of time without the need to place targets, the field of Deformation Monitoring has remained as one of the few unable to implement this technology.
The reason behind this is none other than the vast amounts of data that LiDAR provides. But, this advantage becomes a weakness at the post-processing stage, where the analysis of large data sets acquired regularly presents a challenge.
Hence, OPSIS was developed to overcome the impediments previously described. The idea within its core is to perform operations over the raw data provided by the LiDAR to get a significantly smaller data set.
For the results obtained from the analysis of this sub-dataset have to be equivalent as those we would obtain evaluating the original, the operations involved must ensure to preserve the spatial information contained within the input data.
LiDAR provides us with multidimensional spatial information in the form of point clouds. After going through a filtering process to eliminate the outliers or noise, the first calculation performed is the projection of each point of said cloud over a mathematically defined surface.
Determination of the type of surface and its defining parameters is done on the basis of best-fit adjustment to the specific point cloud. From this moment on, we have the ability to display our three-dimensional data on a two-dimensional representation, although the volume of data we have to work with remains the same, as we still gather the same number of points defined by 3 parameters (coordinates on the projection surface and distance).
To resolve the obstacles presented by the extensive amount of data, the second transformation of the data is performed. Said transformation is the tessellation of the 2D representation using a square grid of adjustable size. The points contained in each cell are the subject of a statistical analysis focused on the distance from each point to the surface, obtaining a mean deviation value for each grid’s cell. Setting a maximum deviation value, the cells are classified into two categories, accepted and rejected. The values of those accepted cells are the subject of the deformation analysis, thus achieving the goal of obtaining a reduced data set to analyse.
Figure 2: 3D Tunnel Template Creation Using OPSIS
The task of monitoring the deformations or displacements of the scanned objects to perceive possible changes using OPSIS comes down to processing the subsequent point clouds obtained in different epochs using the same projection surface and grid obtained as the best fit for the initial point cloud.
If significant changes in the object’s geometrical form were to occur, variations of the cell’s mean values will make them easily detectable. What is differentiating this approach from the commonly used existing software, is that this is not just a point cloud pair comparison. It is also a linear diagram visualization of the deformation history of each grid cell.
OPSIS software can be used to monitor
Road Pavements: Watch the demo video below on how the OPSIS software analyses laser scanner data of road surfaces and provides you with complete deformation overview maps, time-displacement graphs and animated images.
Nuclear Power Plants
Buildings, Monuments: Watch the below demo video on how the OPSIS software analyses laser scanner data of buildings and provides you with complete deformation overview maps, time-displacement graphs and animated images at a glance.
Open Pits, Landslide, and Slopes
Figure 3: High-Rise Building Projection Using OPSIS
OPSIS analysis software has several features that make it one of its kinds. Some of them include:
Limitless point cloud comparison
Full surface deformation maps
Time-lapse animation of deformation maps
Customization of projection mathematical template and results’ grid
Multiple templates within the same project
Custom colour scales
Custom alert, alarm and action level per template
Imports .las, .pts, .e57, .ply, .xyz files
Export in pdf, XML and CSV format
OEM noise filtering
Automatic elimination of points away from the template’s surface
Just 2 clicks and 2 seconds from importing a point cloud to the viewing of the report
The software provides the complete coverage of the structure’s surface – monitor in between other installed sensors
It saves the risk of installing prisms at dangerous locations thereby, saving human life
The software eliminates possibilities of accidents such as traffic and construction site mishaps
It provides thorough and in-depth monitoring data
It eliminates the installation of targets and provides immediate baseline readings.
It is much faster than total stations and optical 3D measurements
It provides point clouds comparison results within a few seconds
It focuses only on the problematic areas thereby, reducing the cost and time as well.
It analyses the problem in advance and takes corrective action immediately thus, saving on costly repair work later
The software eliminates accessibility or installation permits
It doesn’t hinder the construction work
The fast speed scanning ensures evenly distributed environmental effects – wind speed, solar radiation, temperature, refraction, etc. over the monitoring duration.
It provides an overview of the total map(s) of deformations.
The software understands the history with long-term time-displacement graphs.
It interprets by correlating data with other parameters – wind speed, water table, total pressure, temperature, etc.
OPSIS is indeed an effective, as well as, smart solution that can be used for analysing Laser Scanning data for effective structural deformation monitoring. This was a brief on OPSIS – the deformation analysis software developed by Encardio Moniterra Group with over 52 years of expertise, knowledge, and experience.
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