Recently, I wanted to learn more about Synthetic Aperture Radar (SAR) technology, and found it very vague and mysterious, despite it being invented in 1951!! So this is my attempt to gather information and summarize in simple plain language and terminology.
Definition:
SAR stands for Synthetic Aperture Radar. This means:
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Synthetic: artifical, not real or genuine.
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Aperture: this part of "SAR" confused me, as the definition of aperture is an opening, such as a hole or gap. Aperture is commonly used in photography, describing the width of the hole in which light passes through. In the context of SAR, the aperture is the size of the antenna that recieves the signal, and, the reason it is "synthetic" is because it uses the movement of the antenna, in most cases the movement along an orbit, to artifically increase the size of the aperture. i.e. it is "faking" the aperture size by moving in a certain direction.
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Radar: stands for Radio Detection and Ranging; a device for determining the presence and location of an object by measuring the time for the echo of a radio wave to return from it and the direction from which it returns.
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so SAR actually has an acronynm nested in the acronym. the long form is: Synthetic Aperture Radio Detection and Ranging.
Applications:
- SAR can be used for a miltary or government, SAR is useful for spying on other countries, for example identifying vehicles, ships and troop movement from another country, it could be an adversary or an ally. For example, a country could spy on an adversary to look for vehicles, tanks, aircraft, ships, or to track movement. Another example would be a country "verifying" another country's assets.
- SAR is useful for understanding the conditions after a major natural disaster such as a hurricane, tornado, flood or earthquake. SAR can show where floodwaters are, where a fire is burning, and changes in the height of the ground, which could change after an earthquake. SAR could also monitor the changes in geometry of a volcano to better understand and predict eruptions.
- SAR can be used to measure the geometry of the Earth, much like you would measure the size of furniture. This would indicate the slope of a hill or mountain, or the corresponding heights.
- SAR can detect changes to the Earth's suface caused by water erosion, excavation, landslide, or even if a vehicle has driven across a homogenous surface like a field or desert. SAR is very sensitive to small changes in height.
- SAR can help scientists determine areas with a risk of landslide.
- SAR can help engineers with construction projects, or monitor infrastructure such as the stuctural integrity of bridges, buildings and freeways.
- SAR can also monitor the integrity of costly infrastructures in the oil, gas and mining industries
Reference material:
- I found this to be very helpful, although it is technical https://asf.alaska.edu/information/sar-information/what-is-sar/
- Helpful overview and diagrams https://pro.arcgis.com/en/pro-app/latest/help/analysis/image-analyst/introduction-to-synthetic-aperture-radar.htm