{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,21]],"date-time":"2026-03-21T20:06:18Z","timestamp":1774123578609,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2021,3,12]],"date-time":"2021-03-12T00:00:00Z","timestamp":1615507200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010661","name":"Horizon 2020 Framework Programme","doi-asserted-by":"publisher","award":["project No 776335,"],"award-info":[{"award-number":["project No 776335,"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The effectiveness of radar interferometric techniques in non-urban areas can often be compromised due to the lack of stable natural targets. This drawback can be partially compensated through the installation of reference targets, characterized by a bright and stable radar response. The installation of passive corner reflectors (PCR) often represents a valid aid, but these objects are usually cumbersome, and suffer from severe weather conditions; furthermore, the installation of a PCR can be difficult and costly, especially in places with hard accessibility. Active reflectors (AR) represent a less cumbersome alternative to PCRs, while still providing a stable phase response. This paper describes the design, implementation, and test of an AR prototype, designed to operate with the Sentinel-1 synthetic aperture radar (SAR), aimed at providing a fair performance\/cost benefit. These characteristics, obtained through a tradeoff between the use of off-the-shelf components and a simple architecture, can make the setup of a dense network (i.e., tens of devices) in the monitored areas feasible. The paper reports the design, implementation, and the analysis of different tests carried out in a laboratory, and in a real condition in the field, to illustrate AR reliability and estimate its phase stability.<\/jats:p>","DOI":"10.3390\/s21062008","type":"journal-article","created":{"date-parts":[[2021,3,14]],"date-time":"2021-03-14T23:52:06Z","timestamp":1615765926000},"page":"2008","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["A Low-Cost Active Reflector for Interferometric Monitoring Based on Sentinel-1 SAR Images"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8924-9029","authenticated-orcid":false,"given":"Guido","family":"Luzi","sequence":"first","affiliation":[{"name":"Centre T\u00e9cnologic de Telecommunicacions de Catalunya (CTTC\/CERCA), Division of Geomatics, Av. Gauss 7, Castelldefels, E-08860 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4152-5888","authenticated-orcid":false,"given":"Pedro F.","family":"Esp\u00edn-L\u00f3pez","sequence":"additional","affiliation":[{"name":"Centre T\u00e9cnologic de Telecommunicacions de Catalunya (CTTC\/CERCA), Division of Geomatics, Av. Gauss 7, Castelldefels, E-08860 Barcelona, Spain"}]},{"given":"Ferm\u00edn","family":"Mira P\u00e9rez","sequence":"additional","affiliation":[{"name":"Centre T\u00e9cnologic de Telecommunicacions de Catalunya (CTTC\/CERCA), Division of Geomatics, Av. Gauss 7, Castelldefels, E-08860 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2505-6855","authenticated-orcid":false,"given":"Oriol","family":"Monserrat","sequence":"additional","affiliation":[{"name":"Centre T\u00e9cnologic de Telecommunicacions de Catalunya (CTTC\/CERCA), Division of Geomatics, Av. Gauss 7, Castelldefels, E-08860 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8545-5490","authenticated-orcid":false,"given":"Michele","family":"Crosetto","sequence":"additional","affiliation":[{"name":"Centre T\u00e9cnologic de Telecommunicacions de Catalunya (CTTC\/CERCA), Division of Geomatics, Av. Gauss 7, Castelldefels, E-08860 Barcelona, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2021,3,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1109\/36.898661","article-title":"Permanent scatterers in SAR interferometry","volume":"39","author":"Ferretti","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.isprsjprs.2015.10.011","article-title":"Persistent scatterer interferometry: A review","volume":"115","author":"Crosetto","year":"2016","journal-title":"ISPRS J. Photogramm. 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