Synthetic-aperture radar system and operating method for monitoring ground and structure displacements suitable for emergency conditions

• US 20110298655A1
• Filed: 06/07/2010
• Published: 12/08/2011
• Est. Priority Date: 06/07/2010
• Status: Active Grant

• Current Assignee: Ellegi Sri
• Original Assignee: Ellegi Sri
• Inventors: Leva, Davide, Rivolta, Carlo
• Granted Patent: US 8,384,583 B2
• Time in Patent Office: Days
• US Class Current: 342/25.C
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A synthetic-aperture radar system, and related operating method, for the monitoring of ground and structure movements, particularly suitable for emergency conditions, characterized by a ground based platform with polarimetric capabilities, that able to quickly acquire, embeddedly process and post-process data by a novel data acquisition “On the Fly” mode of operation, reducing by at least an order of magnitude the data acquisition time. The inventive system characteristics allows to achieve on-field measurement results on three-dimensional maps georeferenced to absolute coordinate systems (WGS84, Gauss-Boaga, and so on). The operating method includes the step of installing the system, the acquiring of the first measurements, the quick data processing and post-processing to provide sub-millimetric precision georeferenced bi-dimensional and three-dimensional displacement maps for the objects belonging to the monitored scenario, with an improved performance and in a measurement time compatible to that required in an emergency condition, with an higher degree of integration with other sensors and autonomously and embeddendly.

Claims

1. A synthetic aperture radar system for monitoring ground and structure movements, characterized by a ground based platform equipped with an interferometric and polarimetric sensor able to perform measurements while moving at a constant speed;

said system is equipped with an embedded power supply and connection unit, a linear positioner provided with a movable carriage, and a measuring head;

the system is also provided with the following operating modules;

an embedded main system control unit, an embedded electromagnetic wave generator and receiver, a motor control and managing unit, an embedded UPS module including an embedded buffer battery;

an I/O managing module, an embedded calibrated videocamera or photocamera, an embedded GSM/GPRS/UMTS modem, an embedded GPS receiver, an embedded display and an alphanumeric keypad, an embedded LAN module, an embedded WLAN module, an embedded mass storage module, and embedded standard interfaces for assembling laser scanners and topographic instrument reflectors;

all the system mechanical components being provided with unique reference marks and points or connections allowing them to be assembled, disassembled and replaced within a dimensional tolerance limit range as required by application.

2. A synthetic aperture radar system, according to claim 1, characterized in that, to perform a measurement, the radar system starts to drive the measuring head along a linear track with a constant speed and without stopping at discrete step of said linear track using “

on the fly”

acquisition mode;

during the constant speed movement, the system acquires the data needed to process a single radar image;

the scanning time of this mode of operation is much shorter compared to the one performed by a conventional “

stop &

go”

mode of operation the system achieves a perfect synchronization of the acquired signal with the instantaneous position of the carriage by one of the following alternative methods;

a physical embedded trigger generated by the embedded microwave module, a physical embedded trigger generated by the rotary encoder or by a linear encoder. Alternately it is possible to simulate the synchronization with a software trigger;

in which for the complex number matrix saved on the embedded mass storage module to be focalized into a radar image is the result of a bi-dimensional interpolation of measurements acquired at all the bursts which have been transmitted and received along all the linear unit, oversampling the data.

3. A synthetic aperture radar system, according to claim 1, characterized in that said embedded videocamera or photocamera is of a calibrated digital type and allows, by photogrametic methods, to reconstruct or acquire a digital terrain model of the ground and ground representing point clouds;

said embedded calibrated digital videocamera or photocamera is built-in in the movable measurement head and is calibrated in a way that, by driving it along the track together with the movable measurement, different position snapshot sequences may be acquired;

a set of said snapshot sequences allows to achieve, through multifocal algorithms, point clouds or digital models indicative of a ground elevation of the analyzed area.

4. A synthetic aperture radar system, according to claim 1, characterized in that said GPS module is embedded in the measurement head and provides an absolute position of the carriage at discrete step on the track, thereby, from a set of track carriage step position measured along the track it is possible to retrieve the coordinates of the middle point of the track, that is the system installing point, and its spatial direction according to a geographic coordinate system external and independent from the system;

so as to allow to georeference said radar system results to an external coordinate system such as the WGS84 or the Gauss-Boaga coordinate system.

5. A synthetic aperture radar system, according to claim 1, characterized in that said linear positioner comprises a plurality of plates and counter-plates;

said counter-plates are clamped to tripods;

said plates surfaces are equipped with a embedded preset assembly for performing standard connections for mounting topographic instrument, such as theodolite and total station detecting mirror elements;

said connections consist in an embedded vertical shaft including a top slot mating with a detector mirror or reflector hollow shaft;

thereby allowing to georeference the radar system results into a main coordinate system, such as the WGS84 or the Gauss-Boaga system.

6. A synthetic aperture radar system, according to claim 1, characterized in that the said embedded calibrated digital videocamera or photocamera, the embedded GPS module, and the embedded standard connection counter-plates allow to measure the system spatial positions and to achieve a digital elevation model of the monitored area, the system is able to produce embedded on-field results in a three-dimensional system georeferenced to an outer and known geographic coordinate system such as the WGS84 or the Gauss-Boaga coordinate systems.

7. An operating method for operating a synthetic aperture radar system according to claim 1, wherein said radar system is quickly installed by using, as a base therefore, quickly deployable mechanical tripods;

quickly wiring of the system by only two quickly connectable cables;

starting the system and setting-up the measurement parameters through an embedded display and an embedded alphanumeric keypad;

acquiring the first measurements in a measurement time as shorter as possible;

processing and post-processing data in a few seconds thanks to a embedded control and managing module;

thereby the provided embedded bi-dimensional or three-dimensional maps of the monitored scenario are available in a period of few minutes after having on-field installed the instrumentation, so to provide an useful support for emergency condition decisional steps.