Monitoring method comprising: • integrally coupling a first electromagnetic mirror of passive type (10,13,18,25) and a given target (7,14,17,24,30) to be monitored, wherein said given target is not visible, or not always visible, or partially visible to synthetic aperture radar; • integrally coupling a second electromagnetic mirror of passive type (11,20) and the given target (9,17,30), or installing the second electromagnetic mirror of passive type (15,26) in a given fixed position in a given area of the earth's surface where the given target (14, 24,30) is located; and • monitoring over time the given target (7,9,14,17,24,30) by - acquiring SAR images of the given area of the earth's surface at different times by means of one or more synthetic aperture radar(s) installed on board one or more satellites (12,16,22,27,29) and/or one or more aerial platforms, - computing, by means of a processing unit, a respective distance between the first electromagnetic mirror (10,13,18,25) and the second electromagnetic mirror (11,15,20,26) in each acquired SAR image, and - determining, by means of the processing unit, a mutual displacement of the first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors on the basis of the computed distances between said first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors in the acquired SAR images; wherein no interferometric technique is used. • integrally coupling a first electromagnetic mirror of passive type (10,13,18,25) and a given target (7,14,17,24,30) to be monitored, wherein said given target is not visible, or not always visible, or partially visible to synthetic aperture radar; • integrally coupling a second electromagnetic mirror of passive type (11,20) and the given target (9,17,30), or installing the second electromagnetic mirror of passive type (15,26) in a given fixed position in a given area of the earth's surface where the given target (14, 24,30) is located; and • monitoring over time the given target (7,9,14,17,24,30) by - acquiring SAR images of the given area of the earth's surface at different times by means of one or more synthetic aperture radar(s) installed on board one or more satellites (12,16,22,27,29) and/or one or more aerial platforms, - computing, by means of a processing unit, a respective distance between the first electromagnetic mirror (10,13,18,25) and the second electromagnetic mirror (11,15,20,26) in each acquired SAR image, and - determining, by means of the processing unit, a mutual displacement of the first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors on the basis of the computed distances between said first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors in the acquired SAR images; wherein no interferometric technique is used. - acquiring SAR images of the given area of the earth's surface at different times by means of one or more synthetic aperture radar(s) installed on board one or more satellites (12,16,22,27,29) and/or one or more aerial platforms, - computing, by means of a processing unit, a respective distance between the first electromagnetic mirror (10,13,18,25) and the second electromagnetic mirror (11,15,20,26) in each acquired SAR image, and - determining, by means of the processing unit, a mutual displacement of the first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors on the basis of the computed distances between said first (10,13,18,25) and second (11,15,20,26) electromagnetic mirrors in the acquired SAR images;