Interferometric synthetic aperture radar InSAR
This Envisat Advanced interferometric synthetic aperture radar (InSAR) interferogram over the Kenyan section of the Great Rift Valley shows small surface displacements that are not visible to the naked eye of the Longonot volcano (front right). In the background is Suswa volcano, which was not deforming at this time. Using InSAR, a group of scientists discovered that from 1997 to 2000 the volcanoes at Suswa and Menengai (not visible) subsided 2cm to 5cm, and between 2004 and 2006 the Longonot volcano experienced uplift of around 9cm (pictured). Interferogram images appear as rainbow-coloured interference patterns. A complete set of coloured bands, called 'fringes', represents ground movement relative to the spacecraft of half a wavelength, which is 2.8cm in the case of Envisat's InSAR. |
Contents |
[edit] Introduction
Interferometric synthetic aperture radar (abbreviated as InSAR or IfSAR) is a technique that uses satellite or aircraft radar signals from multiple sources to capture complex and precise measurements.
[edit] Where it can be used
InSAR is a highly effective way to measure changes in land surface altitude. The technique uses two or more synthetic aperture radar (SAR) images and ‘interferes’ them to interpret differences and produce interferograms. This is an accurate way of detecting ground movements and can be scaled from single pixels (typically 3m x 3m or 4m x 14m) to entire countries.
Radar waves can be transmitted through most weather conditions and do not require daylight.
[edit] Geophysical disaster detection
The deployment of InSAR was first investigated in the 1980s, with additional exploration in the 1990s. One of the earliest practical applications of InSAR came in 1992, when it was used to measure the after effects of an earthquake in California.
Since those early applications, InSAR has been used to record data associated with landslides, volcanoes and other natural occurrences. In these instances, geotechnical engineers use InSAR as a safe, remote sensing technique for assessing and monitoring movement.
[edit] Subsidence
InSAR has proven effective at recording millimetre-scale shifts of land (such as subsidence). Subsidence can be tracked using historic satellite radar data covering previous decades and then monitored throughout the duration of a project and beyond.
InSAR has also been useful in recording the consequences of subsurface mining and natural resource extraction (both current and historic).
[edit] Structural instability
InSAR can also be used to record the stability of infrastructure (including highways, rail, dams and so on) and to monitor buildings. Movements can occur for a multitude of reasons - inadequate design or poor construction of foundations - but it can be difficult to capture the historic data.
NB Earth observation and aerial surveys, RICS professional standard, 6th edition, September 2021, published on 4 January 2022 by the Royal Institution of Chartered Surveyors (RICS), defines interferometric synthetic aperture radar (InSAR) as: ‘The measurement of the differences in the phases of the waves between two SAR images acquired over the same area at different times.’
[edit] Related articles on Designing Buildings
- Construction drones.
- Digital mapping and cartography.
- Earthquake Design Practice for Buildings.
- Engineers and hurricanes.
- Future proofing construction.
- Geophysical survey.
- Global positioning systems and global navigation satellite systems.
- LiDAR.
- Radar.
- Site surveys.
- Subsidence of buildings.
- Synthetic aperture radar.
- Using satellite imagery to monitor movements in megaprojects.
Featured articles and news
The continued ISG fall out, where to go?
Support for ISG contractors, companies and employees.
New HES national centre for traditional building retrofit
Announced as HES publishes survey results which reveal strong support for retrofit.
Retrofit of Buildings, a CIOB Technical Publication
Expected to become one of the largest activities in the global construction industry.
The ECA industry focus video channel
Keeping update with the industry session by session.
Over 25 recorded informations sessions freely available.
AT Awards 2024 ceremony East London October 25th.
Revisiting the AT community at the 2023 awards evening.
The Community Housing Fund and built affordable homes
CLTN reviews the impact of the Fund and calls for extension.
The grading system of the Regulator for Social Housing
A background, an explanation and ten recent enforcements.
Construction, repair and maintenance. Book review.
Putting new life into a city with a 1900 year history.
BSRIA Briefing 2024: Sustainable Futures speakers
Redefining Retrofit for Net Zero Living 22 Nov.
Wall of support for post-Grenfell regulation of electricians
Call for a shake-up of the construction industry highlighted on radio.
Digital sustainability through future AEC tools
Bringing together industry and academia to meet challenges.
Skills gap for net zero highlighted to Minister for Industry
ECA convenes roundtable discussion at Portcullis House.
Evidencing Net Zero with the new UK buildings standard
Pilot version with detailed excel proforma out now!
Scottish Building Safety Levy, in consultation
From direct remediation and the RPDT, to the costs and alternatives.
Waves of warmer homes grants for the rental sector
Boosting energy efficiency standards for all rented homes.
A refocus of the National Planning Policy Framework
Key terms described in brief, as the consultation closes the evening of the 24th.
Fortified farmhouses of the unruly 16th-and 17th-century borders.