Spotify Linkedin
Podcast Concretely Episode - inSAR for bridge maintenance

Can Satellites Predict Bridge Collapses?

[tta_listen_btn listen_text="Listen" pause_text="Pause" resume_text="Resume" replay_text="Replay"]
Podcast Concretely Episode - inSAR for bridge maintenance

Millimeter Precise Monitoring of Bridges With InSAR

InSAR (Interferometric Synthetic Aperture Radar) is emerging as one of the most powerful technologies for modern infrastructure maintenance. As explained by Alois Vorwagner from the Austrian Institute of Technology (AIT), InSAR enables—for the first time—cost-efficient, large-scale and millimeter-accurate monitoring of bridges, roads and railways directly from space.

This article summarizes how InSAR works, its precision and limitations, practical applications and future potential—based entirely on your transcript.

How InSAR Technology Works

InSAR uses radar satellites that send electromagnetic waves to the Earth’s surface and compare the reflected phase over time. Tiny differences between satellite passes reveal ground and structural movements in the millimeter range.

Radar principle

  • Satellites emit microwaves (e.g., Sentinel-1 at 5.4 GHz, wavelength approx. 6 cm).

  • Returns are compared across many satellite orbits.

  • Stable reflectors—such as bridge piers, barriers or signposts—become Persistent Scatterers.

  • Phase differences allow computation of vertical and horizontal displacements with high precision.

Ground resolution

  • Sentinel-1 provides ground pixels of roughly 20 × 5 meters.

  • Each pixel contains at most one persistent scatterer.

  • Therefore, structures need to cover several pixels for reliable interpretation.

  • As stated in the transcript:
    → Bridges larger than approx. 20 meters can be reliably analyzed with Sentinel-1.

Advanced processing

AIT developed methods to correct temperature-related expansions, significantly improving structural interpretation and enabling insights such as pier movements or relative displacements across spans.

Accuracy & Limitations of InSAR

Millimeter precision

With temperature compensation, AIT achieved better than 2 mm accuracy on multiple bridges—independent of how many scatterer points were available.

Frequency of measurements

  • Sentinel-1 revisits the same orbit approximately every 6 days (ascending or descending).

  • Identical viewing geometry typically every 12 days.

  • Because Sentinel-1 consists of a satellite pair, intervals may be shorter.

Line-of-sight limitation

InSAR measures only along the satellite’s slanted line of sight (LOS):

  • Vertical and east–west movements are highly visible.

  • North–south movements are almost invisible to the satellite.

  • True 3D displacement requires assumptions or multi-orbit combinations.

Data availability & delays

  • ESA provides centrally preprocessed datasets only once per year.

  • Raw data are available weekly, but require heavy processing.

  • Full automated pipelines are still under development.

Topographic visibility

  • Mountainous terrain can block the radar beam—an issue in regions like the Alps.

  • In flat areas (example from Northern Germany), up to 90% of bridges within 100 km were measurable.

Corner reflectors

Where natural scatterer points are missing, corner reflectors—simple metallic structures—provide:

  • very strong radar returns

  • precise identification of the measurement point

  • a low-maintenance, long-term reference for InSAR monitoring

Practical Use of InSAR for Infrastructure Maintenance

1. Network-wide hotspot detection

One of the greatest advantages of InSAR is the ability to monitor entire infrastructure networks—roads, railways, pipelines—in a single analysis.

Example from the transcript:

  • A 40–50 km motorway segment (A14, Austria/Swiss border) was processed.

  • InSAR detected:

    • known problem bridges

    • previously unknown deformation hotspots

    • differential settlement between new embankments and adjacent bridges

  • Historical data back to 2019 allowed trend analysis.

This turns InSAR into an ideal early-warning and prioritization tool for asset managers.

2. Detailed structural behavior of individual bridges

InSAR revealed:

  • annual deformation patterns

  • upward and downward pier movements

  • differential movements between bridge sections

  • blocked or freed bearings (detectable through abnormal or absent temperature response)

This transforms InSAR into a digital long-term “health record” for major structures.

3. Recommended KPIs for asset managers (based on transcript insights)

  • Annual settlement rate (mm/year)

  • Trend: increasing / stable / decreasing

  • Hotspots per 10 km of network

  • Temperature–displacement correlation

  • Relative pier movement (mm)

  • Long-term deformation curve from 2019 to present

4. Examples from Austria

  • Pilot projects with ÖBB (railways) and ASFINAG (motorways).

  • Several large valley bridges monitored with <2 mm precision.

  • Urban tunnel construction: long-term settlement monitoring.

  • Flood protection dikes and embankment behavior analyzed using InSAR data.

In all cases, InSAR acted as a scalable monitoring layer, with on-site sensors used only where necessary.

The Future of InSAR in Infrastructure Maintenance

Based on the transcript, several trends will shape the coming decade:

1. Higher-resolution satellites

Future radar missions will offer:

  • improved ground resolution (<10 m)

  • shorter revisit intervals

  • better atmospheric corrections

  • increased stability for LOS analysis

2. Integration into national asset management

A strong opportunity exists for governments and infrastructure owners:

  • nationwide screening

  • automatic alerts about abnormal movement

  • unified access for all asset operators

  • integration into bridge databases and road information systems

3. Hybrid monitoring strategies

The optimal approach will combine:

  • InSAR for large-scale trend detection

  • local sensors for high-frequency and short-term behavior
    This reduces costs while increasing safety and prediction quality.

4. Quantum computing

As Alois mentions, quantum computing may become the next major leap:

  • significantly faster processing

  • near-real-time InSAR analysis

  • potential for higher precision and automated deformation modeling

Conclusion: InSAR Will Become a Key Technology for Future Infrastructure Maintenance

The insights from your transcript are clear:
InSAR provides scalable, cost-efficient and highly accurate monitoring for thousands of structures simultaneously.

With:

  • <2 mm accuracy

  • free satellite data

  • the ability to analyze entire networks (40–50 km and more)

  • historical datasets going back years

  • early hotspot detection and enhanced bridge assessments

InSAR is on track to become a core tool for infrastructure operators in the coming years—especially as global infrastructures age and maintenance demands grow.

Literatur

Share the Post: