Bridge monitoring with satellite data SAR

Civil infrastructure is vital for supporting our life style and economy. However, the prolongued expossure to outdoor weather conditions and time deteriorates the infrastructure. Besides, after some years of decades, the infrastructure do not comply with new construction codes. This problem of infrastructure deterioration is becoming more important because of the increasing number of infrastructure collapses. Thus, it is important to perform a constant monitoring civil infrastructure.Remote sensing synthetic aperture radar (SAR) data provides a new and modern methodology for monitoring civil infrastructure.
How to monitor infrastructure with satellite data SAR?
The reader may be wondering "How satellite data can used to monitor civil infrastructure such as bridges?". The answer is Interferometric SAR (InSAR) and Differential InSAR.
InSAR takes advantage of the interferometric phase of simultaneous observations. Differential InSAR (SInSAR)  considers the interferometric phase of observations acquired at different times. Soussa and Bastos (2013) explain the concept of DInSAR with Figure 1. Two SAR observations at times T1 and T2 will show the deformation DR.
Figure 1. DInSAR concept (Source: Soussa abd Bastos 2013)

Several studies are beginning to take advantage of DInSAR for monitoring bridges. Soussa and Bastos (2013) analyzed ERS SAR observation of the Hintze Ribeiro centennial bridge in Portugal. The bridge collapsed in 2001 when one of its piles collapsed. The study showed that between 1995 and the collapse date the collapsed pile had vertical displacements up to -20 mm yr-1, where the negative sign means that it was sinking. Other example. In 2012, Cusson et al., (2012) made a similar study at larger scale in Vancouver and Montreal, Canada. More important than the number of examples however, is the fact that SAR data proved to be an important data source for monitoring civil infrastructure and finding hidden information in collapsed infrastructure.
Figure 2. Collapsed Hintze Ribeiro centennial bridge (Cource: StockClip)
Satellite monitoring or in situ monitoring?
Civil infrastructure can also be monitored by in situ inspections. Thus, we may wonder what are the advantages of SAR monitoring?; Is it better to use SAR monitoring or in situ inspection? Actually, there is no definite answer to the last question; it depends on the specific case. Nevertheless, Cusson et al., (2012) points some of the main advantages of SAR monitoring. Among the advantages of SAR monitoring we can mention:
  • Increased and constant monitoring frequency regardless weather or time
  • Possibility to monitor the whole structure
  • Monitoring regardless accessibility issues.
In further posts we will provide more details and more application cases of SAR data.In you want to know more about DInSAR and SAR application, feel free to contact us.

Oroville dam disaster observed by satellite images

Last days we had several news about the Oroville dam. In this post I will not describe the details of this natural disaster because there are already several sites about that that. Instead, I prefer to provide a visualization of this disaster so that we can understand its magnitude and visualize it. For such purpose I used remote sensing satellite data collected before the disaster and during the disaster. In all the images you can get a full screen image by clicking the image.

The figure shows 2 images observed by the French satellite Spot. The left images was observed on November 11, 2016 (before the disaster), while the right image was observed on February 14, 2017 (during the disaster). The water changes are evident. Before the event we easily visualize the shoreline. Besides, we can also visualize 2 details during the event (right image). A) At the dam we can see a white spot which the water over the spillway, and B) the water in the reach between the dam and Oroville city has different colours because of the mud and earth; you can get a full screen image by clicking the image
Fig 1. Spot image of Oroville dam before the event (left) and during the event (right) Click the image for full screen image

Thanks to Digital Globe, ESA and Gizmodo, we can visualize in more detail what really happened in the auxiliary spillway. The left image shows the spillway before the event, while the right image shows the spillway during the event. We can observe the spillway at full capacity and the auxiliary spillway already collapsed.

Fig 2. Image of Oroville spillway before the event (left) and during the event (right) (Source: Digital Globe, Gizmodo). Click the image for full screen image

 The following image shows in more detail the collapse of the auxiliary spillway and the road.
Fig 3. Image of Oroville spillway before the event (left) and during the event (right) (Source: Digital Globe, Gizmodo). Click the image for full screen image

A spanish version of this post was published at iAgua