System for detecting man-made objects using polarimetric synthetic aperture radar imagery with error reduction and method of use

Patent metadata

Field	Value
Publication number	US-10436897-B2
Application number	US-201715423723-A
Country	US
Kind code	B2
Filing date	Feb 3, 2017
Priority date	Dec 8, 2014
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

A system for determining the location of a man-made object based upon symmetry of the object comprising a receiver configured to receive radar signals comprising cross-polarized and co-polarized responses; at least one processor configured to combine the horizontal-horizontal polarimetric responses and vertical-vertical polarimetric responses to form co-polarimetric images and operate on one or both of the vertical-horizontal polarimetric responses and horizontal-vertical polarimetric responses to form cross-polarized images; the at least one processor configured to process the co-polarized and cross-polarized images to locate areas of interest containing a maximum in the co-pol image and a null state in the co-pol image indicating the potential detection of a man-made object; the at least one processor being configured to filter data using buffer regions and/or skipping of pixels in the vicinity of an area of interest. A method for detection of man-made objects is also disclosed.

First claim

What is claimed is:

1. A system for determining the location of a man-made object based upon symmetry of the object comprising:
a receiver configured to receive radar signals comprising cross-polarized and co-polarized responses, the co-polarized responses measured either by transmitting and receiving both horizontally polarized waves (horizontal-horizontal) or by transmitting and receiving both vertically polarized waves (vertical-vertical); the cross-polarized responses measured by either transmitting horizontally polarized waves and receiving vertically polarized waves (horizontal-vertical) or by transmitting vertically polarized waves and receiving horizontally polarized waves (vertical-horizontal);
at least one processor, the at least one processor configured to process horizontal-horizontal co-polarimetric (co-pol) data, vertical-vertical co-polarimetric data, and one or both of the vertical-horizontal cross-polarimetric data and horizontal-vertical polarimetric data to form co-polarized images and cross-polarized images;
the at least one processor configured to process the co-polarized and cross-polarized images to locate areas of interest containing a maximum in the co-pol image and a null state in the cross-pol image indicating the potential detection of a man-made object; the at least one processor being configured to filter data using buffer regions in the vicinity of an area of interest to reduce error.

2. The system of claim 1 wherein the at least one processor is configured to perform a summation operation on the pixels in the vicinity of an area of interest in the cross-polarized image and normalize the summation total by dividing by the number of pixels in the area summed to obtain a value indicative of the normalized intensity of the background; and wherein the at least one processor is configured to perform a summation operation on the pixels in an area of interest in the cross-polarized image and normalize the summation total by dividing by the number of pixels in the area of interest indicative of the normalized intensity of the area of interest; and wherein the at least one processor operates to divide the normalized intensity of the area of interest by the normalized intensity of the background to obtain a value indicative of the presence of a man-made object.

3. The system of claim 1 wherein the at least one processor is configured to perform a summation operation on the pixels in the vicinity of an area of interest in the co-polarized image and normalize the summation total by dividing by the number of pixels in the area summed to obtain a value indicative of the normalized intensity of the background; and wherein the at least one processor is configured to perform a summation operation on the pixels in an area of interest in the co-polarized image and normalize the summation total by dividing by the number of pixels in the area of interest indicative of the normalized intensity of the area of interest; and wherein the at least one processor operates to divide the normalized intensity of the area of interest by the normalized intensity of the background to obtain a value indicative of the presence of a man-made object.

4. The system of claim 1 wherein the at least one processor is configured to compute a spatial average and divide the spatial average by the intensity of the background and wherein the at least one processor is configured to reduce the value of pixels in an area of interest using a normalization process to thereby reduce effects of background and wherein the at least one processor determines the intensity of the background using the pixels surrounding the area of interest and calculating an average pixel value of the surrounding pixels.

5. The system of claim 4 wherein the spatial average is computed using the equation:

I
filtercross

⁡

(

x
,
y

)

=

∑

i
=
0

N
p

⁢

I
cross

⁡

(

x
,

y
-

⌊

N
p

/
2

⌋

+
i

)

where I cross (x,y) denotes the image from the cross polarimetric radar data pixel at (x,y), where x is the cross-range coordinate, y is the down-range coordinate, N p is the number of pixels used for spatial averaging, and └Np/2┘ denotes the largest integer less than or equal to N p /2, where N p could be equal to zero for the co-polarimetric image.

6. The system of claim 5 wherein the at least one processor determines the effect of background pixels in the cross polarimetric image after skipping a number of pixels m using the equation:

I

cross
⁢

⁢
denominator

⁡

(

x
,
y

)

=

∑

i
=

m
+
1

M

⁢

I

filter
,
cross

⁡

(

x
-
i

,
y

)

+

∑

i
=

m
+
1

Assignees

• Us Secretary Of The Army Army Research Laboratory
• Us Army

Inventors

• Ranney Kenneth Irving
• Wong David Chun
• Ton Tuan That

Classifications

• G01S13/867

  Combination of radar systems with cameras · CPC title

• G01S13/885

  for ground probing (prospecting or detecting using electromagnetic waves G01V3/12) · CPC title

• G01S7/412

  based on a comparison between measured values and known or stored values · CPC title

• G01S13/9076

  Polarimetric features in SAR · CPC title

• G01S13/887

  for detection of concealed objects, e.g. contraband or weapons · CPC title