La Portalada/Punt de Trobada

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Monitoring - La Portalada Punt de Trobada 2021

The camera autonomously triggers images of the monitored area at least twice daily. It transmits the images to the servers for deformation analysis and preparation for depiction in the user portal. The analysis interval can be selected as required. Deformation analysis is determined nightly and uploaded to the online data portal subsequently. Deformation analyses, all images and live images are accessible anytime through the portal.

The camera autonomously triggers images of the monitored area at least twice daily. It transmits the images to the servers for deformation analysis and preparation for depiction in the user portal. The analysis interval can be selected as required. Deformation analysis is executed by unique algorithms which autonomously select suitable pairs of images and perform a feature tracking analysis for a given time interval. The algorithms are capable to identify features even at strongly varying light conditions. The resulting deformation analysis and the high resolution images are accessible at any time through the data portal. With the help of the deformation analysis and the high resolution images, the responsible staff was able to rapidly and remotely identify the critical areas and take decisions for measures if needed.

The data-portal image viewer offers intuitive and easy image comparison using high-resolution images, zooming even parts of the image. You can quickly switch between cached images to view zones. Also, you can select a set of images. You can zoom in on the image and toggle between the images to check the changes in detail.

The high-resolution pictures allow for zooming and studying details of areas.

The deformation analysis compares pairs of images. This image shows the deformation analysis of the studied area during the installation phase. Initially, images of only two days difference, depicting only fast movements, were compared. With accumulating knowledge and a dataset of the observed region, a comparative framework of 30 days was reached (see picture below). It allowed a deformation sensitivity ten times larger than with the initial configuration.

The number of days in parentheses in the image header (Figures 4 and 5) indicates the range of acceptability to maximize the overall quality of the deformation analysis. The results are displayed in milli-Pixel / day. Color code: • green: regions without significant deformation. • yellow: slow movement. • red to blue: significant deformation. • areas without color: correlation loss due to changes too fast or strong to track, i.e., large movements or rotation objects, or surface change, e.g., induced by snowfall.

Zones 1 to 10 were considered stable, while 11 and 12 were potentially unstable.

The diagram shows how the area was stabilized after the measures. The camera was no longer needed in this case.

Systems

Geoprevent DEFOX^® Deformation Camera

Year of installation

2021

Initial situation

After a vast landslide next to a shopping center and national highway in August 2019, the main access road from Andorra to Spain had to be closed.

Construction measures for safety in this section were initiated. Safety during construction works and the effectiveness of the stabilization measures had to be ensured.

Description

The installation of a Geoprevent DEFOX^® Deformation Camera allowed to distinguish stable areas from unstable areas. The pictures delivered important information about the direction of movement, deformation rates, and velocity time series of defined areas.

The information was used to decide on construction measures, emergency reservoir drains or evacuations (if necessary).

Read more about the La Portalada project in the paper of Roberto Fonseca (March 2022).