<br> [MAS.865](../..) &gt; [Scanning Processes](..) &gt; Synthetic Aperture ## Synthetic Aperture <div style="margin-left:2.5%"> ### Synthetic Aperture Radar (SAR) SAR works similarly to a [phased array](https://en.wikipedia.org/wiki/Phased_array) that can minutiously direct a wave by modulating the phase offset of the signal sent by an array of emitters. In the case of SAR, there is a single antenna (e.g. on a car, space shuttle or other vehicle) that moves. Many advantages: * Complementary information to optical systems * Penetration of radar waves (can measure different properties) * Weather independent (can go through clouds and other atmospheric effects) * Day-and-night imaging * Can get very high resolution, independent from the distance     * [Tutorial on Synthetic Aperture Radar](http://www2.geog.ucl.ac.uk/~mdisney/teaching/PPRS/PPRS_7/esa_sar_tutorial.pdf), Moreria et al, IEEE Geoscience and Remote Sensing Magazine, 2015 * [Slides](https://earth.esa.int/documents/10174/642943/6-LTC2013-SAR-Moreira.pdf) of 2013 * [Synthetic Aperture Radar Interferometry](http://iopscience.iop.org/article/10.1088/0266-5611/14/4/001/meta), Bamler and Harti, Inverse Problems 1998 Different modes: * **Stripmap SAR**: antenna at fixed angle * [An Introduction to Synthetic Aperture Radar: a High-Resolution Alternative to Optical Imaging](https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1012&amp;context=spacegrant) * **Spotlight SAR**: antenna maintained toward target (by rotating, i.e. gimbled antenna) * **Scan SAR**: antenna sweeps a much larger region periodically, covering larger scan area to the detriment of azimuth resolution ### Synthetic Aperture Imaging #### [Synthetic Aperture Confocal Imaging](https://graphics.stanford.edu/papers/confocal/)   * Synthetic Aperture Photography * Use array of 22 mirrors oriented differently (similar to phased array) * Simulate Camera with a wide aperture and a shallow depth of field * Position focal plane on desired target to blur occluder away * Synthetic Aperture Illumination * Replace camera with videoprojector (with coded binary patterns) * Produce real image with similarly shallow depth of field * Position image on statue (for scanning beyond the occluder) #### Synthetic Aperture Audio Imaging   * [Seeing around corners with a mobile phone?: synthetic aperture audio imaging](https://dl.acm.org/citation.cfm?id=2614282), Bedri et al, Siggraph 2014 * [Exploring the Resolution Limit for In-Air Synthetic-Aperture Audio Imaging](http://openaccess.thecvf.com/content_iccv_2015_workshops/w18/papers/Bedri_Exploring_the_Resolution_ICCV_2015_paper.pdf), Bedri, Boufounos and Raskar, ICCV 2015