Abstract:
A system for locating and identifying underground pipes, utilizing a ground-probing radar. The ground-probing radar system includes an antenna module and a transmit/receive sub-system. The system also includes a digital signal processing sub-system for processing the received signal to extract data corresponding to detected differences in dielectric constant and a master controller. The system still further includes a positioning sub-system, a display sub-system, a user interface and a data storage mechanism, display data and said operating parameters.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a system of locating and identifying underground pipes, such as those which carry gas, water and waste to/from homes and building so that, among other things, these pipes can be avoided by excavating equipment or the like. More particularly, the system of the present invention enables the detection of such objects utilyzing, in combination with other novel elements of this invention, ground-probing RADAR. 
     This invention further relates to the RADAR detection of underground pipes, for example, and more particularly relates to a system which focuses a characteristic hyperbolic RADAR response received from an underground object, such as a pipe or other object, utilizing synthetic aperture type technologies, and further processes same to accurately determine said object&#39;s underground position. 
     Accurate RADAR-based underground object detection has always been an elusive goal because of the variability of the ground as a conducting medium in three dimensions, i.e., inherent variations in ground layers, density, obstructions, dielectric constant, etc. Water content, in particular, acutely varies the ground&#39;s dielectric constant which correspondingly attenuates RADAR signals making consistent detection of targets underground difficult at best. Electromagnetic signals transmitted into the ground and reflected from an object buried therein tend to suffer high signal attenuation resulting in low signal-to-clutter and signal-to-noise ratio. Efforts to improve detection ability have found that while a single frequency of operation may be desirable in a particular type soil, the same frequency may be undesirable in another, frequently misinterpreting said objects as ground clutter by conventional underground radar systems. 
     In an effort to overcome inadequacies of conventional underground RADAR detection, U.S. Pat. No.3,831,173 discloses a ground radar system which utilizes a transient signal comprising a wide variety of radiated frequencies, Due to the use of the transient signal, effective reflections are received from a wide variety of underground objects such as pipes, utility lines, culverts, ledges, etc., to depths around 10 feet. The &#39;173 system, however, while appropriate for detecting small conducting objects, is basically unable to accurately detect non-conducting objects with cross-sections of less than one or two feet. 
     U.S. Pat. No. 3,967,282 discloses a detector for detecting both metallic and non-metallic objects, based on differences in the dielectric constants of the object and its surrounding medium, in order to give a location of the object. The &#39;282 invention, however, is burdened with difficulty in processing the received data such that accurate object detection and positioning is not achieved. 
     U.S. Pat. No. 4,706,031 discloses a method and apparatus for identifying a target object located in the ground, in the air or under water. The basis within the disclosure for detection and target identification resides in the apparatus use of the phase deviation between the transmitted and received (echo) radio-wave signals. A signal containing a mixture of various frequencies is transmitted and the return signal or signals are analyzed. A detected difference in phase deviation between the particular frequencies received is used to identify the material properties of the object from which the energy is reflected. The &#39;031 apparatus, however, is still plagued with problems when it comes to detecting small non-conducting objects. 
     U.S. Pat. No. 4,951,055 discloses a ground probing RADAR which includes means for displaying echo images of a buried material. The displayed images are capable of providing a depth direction of the buried material and a movement direction of a moving vehicle carrying the RADAR. The RADAR includes first means for forming a hyperbolic echo image of the material, and causing a hyperbolic echo image to be displayed on the display means, second means for forming a false echo image and causing the false echo image to be displayed on the display means, third means for inputting data to the second means to cause a displayed position of the false echo image to be shifted so that a vertex position of the false echo image and expansion opening thereof coincide with those of the echo image of the buried material, and fourth means for calculating a propagation velocity of the electromagnetic waves in the ground on the data indicative of the vertex position and opening expansion of the false echo image when the two displayed echo images coincide with each other. A position of the buried material is detected on the basis of the propagation velocity value calculated by the fourth means. 
     That is, when electromagnetic waves are emitted from a plurality of points on the ground surface above a buried material, an echo image formed on the basis of data of propagation times of reflected waves at their respective points describes a hyperbola as a result of expansion of the transmitted electromagnetic waves. An operation is carried out to overlap, on the echo image, a false echo image lying in the same coordinate system and consisting of a similar hyperbolic image. If the two echo images are overlapped, a vertex position and an expansion of the opening of the echo image can be determined from the data of the false echo image. Thus, the propagation velocity of electromagnetic waves are calculated from the data that represents the vertex position and the expansion of the opening. The position of the material under the ground is then calculated in relation to the data of propagation time in any position. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a RADAR-based Ground Probing RADAR system which overcomes the shortcomings of the prior art. 
     It is another object of the present invention to provide a ground-probing RADAR system which takes in significant amounts of measurement data during operation, the compilation of which provides for a significant increase in signal-to-noise levels relative prior art underground object-detection systems. 
     It is another object of the present invention to provide a ground-probing RADAR system which displays a productivity that is significantly enhanced relative prior art systems. 
     It is yet another object of the invention to provide a ground-probing RADAR system based on reception of data from only one pass over the underground to be mapped with enhanced detection performance relative prior art ground RADAR systems. 
     It is yet another object of the invention to provide a ground-probing RADAR system with a digital signal processing sub-system which provides a unique method of processing returned RADAR signals with application to geophysical data collection and/or processing. 
     With these objects in mind, a ground-probing RADAR system is disclosed which provides for detection of the presence of all types of underground objects, e.g., buried pipes and cables, at an underground depth of at least 1.5 meters, and an ability to accurately recognize and identify the location and shape of said objects in three dimensions. The mapping system is radar-based, that is, it transmits an electromagnetic pulse and records a response from buried objects. Objects are accurately detected by the system&#39;s unique way of “looking” for a change in dielectric constant within returned (reflected) RADAR signals, enabling accurate detection both metallic and non-metallic targets, such as plastic and concrete pipes, as well as differences in detective material in the ground with three-dimensional distance. 
     A radar response (reflection) from a point object located underground, such as a pipe, embodies a hyperbola or hyperbolic mapping. The system herein detects such point objects by RADAR scanning over the object, receiving the signal reflected therefrom, and generating an image containing a hyperbolic representation of the object from the reflected signal. A dedicated digital signal processor sub-system within the system processes the raw data present in the received, reflected signal to generate a final image of the object to the user. The image is projected or displayed on a specialized display graphical form to indicate the object&#39;s position and estimated depth to a user. The dedicated digital signal processor sub-system accomplishes two primary tasks. The first is migrating or focusing the hyperbolic image from the received signal data to a single point for each radar scan. This “migrating” process is accomplished by the implementation of the digital signal processor sub-system of “clustering” and synthetic aperture radar (SAR) techniques. The second task takes the “migrated” data (i.e., that data consisting of the focused or clustered points) from multiple memory-stored scans and groups the same to extract linear features. The preferred embodiment of the invention may implement a simple SAR or a modified SAR technique (referred to interchangeably herein as super-SAR) which takes into account the relative dielectric constant of the soil (ground). Accordingly, the ground-probing RADAR system accurately computes the target depth. 
     In a first preferred embodiment, a single-channel ground-probing radar system (referred to interchangeably hereinafter as “the Pipehawk system”) is disclosed which operates in accordance with the precepts of this invention. The electronics which enable the unique processing and mapping ability of the present invention, e.g., the Pipehawk system, comprise the following structure. A microprocessor, central to the system&#39;s processing (preferably an Intel 80486 or like device) is electrically connected to a user interface (to be discussed in greater detail below). The microprocessor is electrically connected to a display system including display, softkeys and softkey controller to a location system including a wheel sensor, voltage monitoring means and a dedicated microprocessor or microcontroller; a memory storage device such as a hard disk for storing required data; and a digital signal (DSP) processor, preferably an AT&amp;T DSP326, for performing the unique processing particular to this system. The DSP processor is electrically connected to the RADAR transmitter and receiver sub-system. 
     The Pipehawk system is capable of accurately pinpointing underground objects, e.g., piping, whether plastic or metal, to provide an operator with an immediate display of its location. The Pipehawk RADAR transmitting/receiver sub-system includes a single channel RADAR antenna system comprising a dipole element and dipole element positioning apparatus which coordinates incoming data with data from positioning sensors located in the wheel or wheels. Examples of such element and positioning apparatus are described in commonly owned Great Britain Patent Specification Application Numbers 8629412 and 8629415, respectively, incorporated herein by reference. 
     Operation is accomplished with a user walking the Pipehawk system over the underground to be mapped, at a moderate pace, while a radar scan with the single channel dipole element system is performed repetitively. With each radar scan, the cross-section of the ground corresponding to the center line of the system structure is searched. By carrying out a series of such scans and performing various digital signal processing (DSP) schemes and analysis techniques implemented in the digital signal processor, the Pipehawk system provides a picture of the underground environment. Special features inherent in the system&#39;s design allow for adjustments for the different soil compositions, filter facilitating accurate detection. 
     A second preferred embodiment of the ground-probing RADAR system of this invention includes structure and/or programmed instructions which enable the system to operate in super-sensitive applications. To complement such processing ability, the system (referred to as Pipehawk II) also includes a double channel RADAR antenna sub-system comprising two dipole elements and positioning apparatus. The Pipehawk II system, as well as the Pipehawk system, may embody various structure for various applications, in accordance with those skilled in the art of mechanically engineering and coordinate manufacture of such systems, and in accordance with the several exemplary structural descriptions which will follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a functional system block diagram representing one embodiment of the ground-probing RADAR system of this invention; 
     FIG. 2 is a system flow diagram of the different levels of graphical display screens which are brought up on the system&#39;s display during system operation, in accordance with operator softkey input, in a preferred embodiment of the processing control of the embodiment of FIG. 1; 
     FIGS. 2A,  2 B,  2 C and  2 D are pictorial representations of several of the graphical icons utilized by the system of this invention, as associated with the graphical displays discussed herein with reference to FIG. 2; 
     FIG. 3 is a diagram showing an underground pipe and several block diagrams depicting a particular type of RADAR processing performed by the embodiment of FIG. 1; 
     FIG. 4A shows varying curvatures or hyperbolic representations with increasing depth and dielectric constant of objects detected by the system embodiment of FIG. 1; 
     FIGS. 4B and 4C are graphical representations which together show correlation by the system of FIG. I of stored hyperbolae and raw data, and the resulting outputs; 
     FIG. 4D is a flow diagram of the processing which allows the embodiment of FIG. 1 to identify dielectric range and index; 
     FIG. 5 is a graphical representation of a line in image space generated by the embodiment of FIG. 1; 
     FIG. 6 is a graphical representation of a point in accumulator space generated by the embodiment of FIG. 1; 
     FIG. 7 is a pictorial representation of data processing performed on raw RADAR data of up to 30 scans, Hough transformation to a 7-layer mapping and summation and Hough transform to generate an integrated map or processed output by the unique digital signal processing of this invention; 
     FIG. 8 is a block diagram representing digital signal processing which may be implemented by the invention; 
     FIGS. 9A and 9B are pictorial representations of data processing which together convey how the synthetic aperture technique correlates a set of point-object generated hyperbolic data with raw data; 
     FIG. 10 is a plot of depth buckets reflecting varying depth of the same target; 
     FIG. 11 is a plot of target data reflecting variance of hyperbolic representation with the varying depth of the target; 
     FIG. 12 is a plot of target data in which each of the three depth-varied hyperbolic responses, as shown in FIG. 11, of the varying target depth buckets of FIG. 10, when superimposed as a reference; 
     FIGS. 13,  14 ,  15  and  16  are sequential pictorial flow representations of one form of two dimensional processing of hyperbolic response data performed by this invention; 
     FIGS. 17,  18 ,  19  and  20  are sequential pictorial flow representations of multiple target detection processing performed by this invention; 
     FIG. 21 is a sequential, pictorial flow representation of the resulting fill scan of the stacking of each data layer generated in processing; 
     FIG. 22 is a sequential, pictorial flow representation of processing results associated with target location for each ground level processed, and amplitude detection implemented in accordance with the processing steps defined herein; 
     FIG. 23 is a plot of normalized amplitude against dielectric constant (ER) which exemplifies the system&#39;s ability to determine the correct dielectric constant in the ground being mapped by his invention; 
     FIGS. 24 and 25 are sequential, pictorial flow representations which together represent a preferred method of cluster processing as depicted by the blocks of FIG. xxx; 
     FIGS. 26,  27  and  28  are, respectively, a bottom plan view, a side view and a top plan view of a physical implementation of the first embodiment or Pipehawk system of this invention; 
     FIG. 29 is a more detailed view of the embodiment depicted in FIGS. 26,  27  and  28 ; 
     FIG. 30 is a general schematic diagram depicting the system level design of the embodiment shown in FIGS. 26,  27  and  28 ; 
     FIGS. 31A and 31B are schematic representations of delay coils for use within the antenna module of this invention; 
     FIGS. 32A,  32 B and  32 C are schematic representations which together define one embodiment of an antenna feed element which can be used herein; 
     FIGS. 33A,  33 B and  33 C are schematic representations of a connector assembly which can be used herein; 
     FIGS. 34A and 34B are schematic representations which together depict the element structure and layout for one embodiment of a two-element array as used herein; 
     FIGS. 35A,  35 B,  35 C,  35 D and  35 A are schematic representations of mounting and feed elements which can be used herein; 
     FIGS. 36A,  36 B,  37 A,  37 B,  37 C,  38 A,  38 B,  38 C and  38 D are schematic representations of various hardware elements which may be used herein; 
     FIG. 39A is a top plan view of the handle gripped by the user of the system of the present invention; 
     FIG. 39B is a left side elevational view of the handle of FIG.  39 A. 
     FIGS. 40A,  40 B,  40 C,  40 D,  40 E and  40 F are schematic representations of various hardware elements for use herein, in conjunction with Table A; 
     FIGS. 41A,  41 B,  41 C and  41 D are schematic representations of various hardware elements for use herein; 
     FIG. 42 is a flow block diagram representing the two-channel RADAR (Pipehawk II) system&#39;s internal bus architecture; 
     FIG. 43 is a timing diagram of the multi-channel architecture of the architecture of FIG. 42; 
     FIG. 44 is a pictorial representation of an antenna measurement path generated by the Pipehawk II; 
     FIG. 45 is a copy of a photograph of a two channel experimental rig or platform of the Pipehawk II embodiment; 
     FIGS. 46A and 46B are pictorial representations of an antenna measurement path in a dense pipe and open pipe environment generated by Pipehawk II; 
     FIGS. 47A and 47B are pictorial representations which show front and side perspective views, respectively, of a hand held dual-channel RADAR system (Pipehawk II) of this invention; 
     FIGS. 48A,  48 B and  48 C are detailed views of specific portions of the embodiment of FIG. 47; 
     FIG. 49 is a flow diagram describing some of the DSP processing implemented by the present invention; 
     FIG. 50 is an electrical schematic diagram of sampling circuitry for use with the present invention; 
     FIGS. 51A and 51B are electrical schematic diagrams, the hardware implementation of which represents a portion of the sampling circuitry for use with the Pipehawk II; 
     FIG. 52 is a copy of a picture of a prototype of the Pipehawk invention which highlights the backplane; 
     FIG. 53 is a copy of a picture of a prototype of the Pipehawk invention which highlights the data port and power connection; 
     FIG. 54 is a copy of a picture of a prototype of the Pipehawk invention which highlights the housing; 
     FIG. 55 is a copy of a picture of a prototype of the Pipehawk invention which highlights the system&#39;s heat dissipation ability; 
     FIG. 56 is a copy of a picture of a prototype of the Pipehawk invention which highlights the system&#39;s display; 
     FIGS. 57 and 58 are copies of pictures of a prototype of the Pipehawk invention which highlights the complete housing; and 
     FIGS. 59A and 59B are schematic flow diagrams which together define one embodiment of the super-SAR processing implemented herein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The ground-probing RADAR system of present invention may embody various physical forms and/or structures. Several embodiments of ground-probing RADAR systems, designed in accordance with the invention, will be discussed in the following description. It must be noted, however, that while the embodiments disclosed are preferred implementations of the inventive concepts comprising the invention, said embodiments are disclosed for exemplary purposes only and are not meant to limit the scope or spirit of the invention in any way. 
     A system level block diagram of a first embodiment of the invention, hereinafter referred to interchangeably as the RADAR or Pipehawk system  10 , is depicted in FIG.  1 . Central to the Pipehawk system&#39;s unique processing is a master controller  12 , preferably an Intel 80486 or like microprocessor device. The master controller  12  is electrically connected to a user interface  14  (to be discussed in greater detail below); a display system  16  including display  18  with softkeys  20  and a softkey controller  22 ; a positioning system  24  including a position controller  26 , position sensor  28 , and voltage monitoring means  30 ; data storage  32 , preferably a hard disk, for storing required system data and parameters; and a digital signal processing (DSP) system  34 , preferably an AT&amp;T DSP326. The DSP system  34  is electrically connected to an antenna module  36  which includes RADAR signal generation  40 , transmission  46  and reception apparatus  50 . 
     It is a unique Hough transform, implemented by the Pipehawk system&#39;s hardware which enables its RADAR, via its digital signal processing system, to “look” for shapes within a set of data points. The RADAR looks for any existing objects in a scan, by correlating linear features within the raw data and grouping said features together. Once the features are grouped together, a line is drawn through the points by the system&#39;s dedicated graphics, i.e., a white line drawn vertically downwards the screen. When such a line is found, it is possible that a pipe exists at the location. An advantage of Hough transform is that it is typically unaffected by point gaps. 
     The Pipehawk system  10  operates on the basic principle that the velocity of a transmitted and received signal is a function of the dielectric constant of the soil in which it travels. That is: 
     
       
         v=c/(ε r ) .05 , 
       
     
     where v is the signal velocity, c is the speed of light and ε r  is the dielectric constant of the soil. If the dielectric constant of the soil is known, the velocity of the signal as well as the target depth can be determined. 
     The master controller  12  implements system integration and operation in accordance with a set of instructions, either ROM-resident software or defined by hard-wired logic circuits. In its preferred form, the operation of the master controller is wholly maintained by the system-based software, hereinafter referred to interchangeably as the system software. One preferred embodiment of the set of instructions, i.e., the system software. Through the system software, the master controller controls user input from the user interface  14  and data transfer to/from the display system  16 , that is, the softkey controller which controls softkey-based (20) data display, as well as memory storage and/or transfer of processed data and user-defined system parameters. Control over all subsystems is provided thereby, including the position controller  26  to control any data and/or data flow from the RADAR system&#39;s  10  positioning system  24 , e.g., a wheel sensor system, and the digital signal processing system  34 , which includes not only a digital signal processor (DSP)  88  which controls processing, but system throughput of all DSP data. 
     As mentioned above, the system software is preferably implemented on an Intel 80846 microprocessor. The code defining the system software operation may be written in any programming language known to those skilled in the art which is able to effectively carry out the functions described hereinbelow. The detailed description of the system operation is conveniently described with reference to the following system software explanation. Accordingly, a preferred system operation and system software operation will now be described with reference to FIG.  2 . 
     FIG. 2 shows the various graphic displays which can be brought up to the display screen upon sequencing-through the softkeys located at the bottom horizontal of the display  20 . Just above the softkeys is located a horizontal portion of the screen which is dedicated to displaying icons associated with the softkey, and the processing initiated by a press of the softkey. At system start-up (boot-up), the coded instructions of the system software generate and send main menu graphics display data to the display screen. The main menu graphics (i.e., software control) present a user with choices representative of the five different types of data processing available in this embodiment. By pressing the softkey proximate the graphic representation (or icon) of the particular processing type, the coded instructions change the processing type and the dedicated softkeys, and refresh the screen with new graphics representative of that level&#39;s available processing (the horizontal marked “MAIN MENU” of FIGS. 2A,  2 B,  2 C and  2 D). New icons are put up on the screen to represent the softkey applications. In other words, the same keys now, if pressed, initiate routines for particularized data review. 
     By pressing the third softkey of the MAIN MENU display  100 , represented by the “adjustable wrench” icon as shown in FIG. 2, the software control takes the user down through the coded instructions one level to the tools graphical display, identified as block  102  in FIG.  2 . If the softkey which is directly in the middle at the main menu level is pressed, representing the “ruler” icon as shown in FIG. 2, the instructions would sequence through to present a survey display graphics, represented by block  116  of FIG.  2 . Pressing the softkey key which is third from the right, proximate the “scan” icon, causes a graphics display  120  representing scan or data collection processing. The softkey which is second from the right, proximate a replay icon, will cause a “sites” graphical display associated with the system&#39;s data review processing to become active. By pressing the softkey located second from the left, proximate the “pipe wrench” icon, processing becomes enabled which is utilized to calibrate or adjust system operation. 
     As mentioned, pressing the key proximate the Tools icon at the main menu level  100  of FIG. 2 offers the user a number of new choices, in a form of reprogrammed softkeys and their associated icons. A scale graphical display  104  presents the user with a level of softkey options directed to scaling all processed data on the screen for the users convenience. A physical characteristic graphical display  106  allows user access (via softkeys and their associated icons) to such characteristics as battery level, temperatures at different points within the system, sensor status, internal status and fan status. A waveform monitoring graphical display  108  represents that processing which will allow the user to monitor and/or control the shape of the raw or averaged signal waveform. An adjust sampling window graphical display  110  allows a user to choose (through softkeys and associated icons) the size of the system&#39;s sampling window to fine tune specific mapping situations. Also, a storage status graphical display allows a user access to memory storage information which could affect processing. 
     As mentioned, pressing the key proximate the survey icon brings up the survey graphical display  116  of FIG.  2 . The survey display presents the user with survey and information data options in the form of softkeys, as well access to a second survey menu display  118 . Together, these displays enable the system  10  to operate as a surveyor&#39;s measurement wheel, measuring in metric or imperial units. 
     As mentioned, pressing the softkey proximate the scan icon brings up a scan display  120  of FIG.  2 . The scan display graphics and associated functioning allow the system to be used as a RADAR and to collect data. The scan display  120  requires user input, via the reprogrammed softkeys, regarding status of the site being (or to be) mapped. In particular, scan display  120  allows the user to access a data collection graphical display  124  either indirectly through an enter information graphical display  122 , or directly from the scan graphical display. At the collect data graphical display  124 , the user is again offered next level options in a form of softkeys whose function is represented by collecting, processing and mapping icons. Pressing each icon&#39;s associated softkey brings up collecting data graphical display  126 , a map mode graphical display  128  and a process option graphical display  130 , respectively. The process options graphical display  130  offers a user a choice of data processing, as well as the access to two more or lower level graphical displays. The first is another process options graphical display  134  and the second is a window start graphical display  132 . From the window start graphical display  132  and associated icons, the user may again move to a new system level in a form of a new window finish graphical display  136 . 
     As mentioned, pressing the softkey proximate the “sites” icon puts up the sites graphical display  138  of FIG.  2 . The graphical display menu asks the operator if he/she wishes to open a new file for a new site survey, or continue adding scan data to the last file. The “list of sites” graphical display allows the user to access stored site information, as well as another level of processing in the form of a display data graphical display  140 . Display data graphical display  140  gives the user options about displaying its stored data, as well as the option to move a next level down to either a map mode graphical display  142  or a process options graphical display  144 . The process options graphical display  144  offers a user the option of particularized processing as well as two other graphical displays, window start graphical display  146  and process options graphical display  148 . Window start allows a user to drop to window finish or exit graphical display  150 . 
     As mentioned, by choosing the pipe wrench icon, the graphical display providing a basis for system calibration and associated processing comes up. It is in the confirm exit icon that a user is required to press a softkey to confirm his/her decision to discontinue processing such that system software control ( and therefore system control) is passed to an external controller. Several representations of softkey associated icons, as well as inference of the action which is taken by the system in response to such a keypress is shown in the key charters listed in numerical order. It must be noted however, that the prior description represents only one possible scheme for implementing system software control available in accordance with this invention, and should not be used in an attempt to limit its scope. 
     FIG. 3 is a general schematic block diagram which exemplifies the RADAR portion of the Pipehawk system  10 , superimposed next to a representation of a section of a pipe buried in the ground. The invention, e.g., the Pipehawk system, operates by introducing a fast risetime electromagnetic pulse signal into the ground, and detecting and processing information contained in the signal returned therefrom. The presence of metal generates a major change in electrical properties, but system  10  is sensitive to other changes such as the presence of plastic, water or air. Scattering of the radiated pulse signal is produced by changes in the ground conditions returns; a small fraction of the radiated electromagnetic pulse signal is received at the antenna module. In FIG. 3, a pulse generator acting as a transmitter  80  feeds an electromagnetic pulse signal to antenna  82  to be radiated into ground  84 . The signal portion returned, i.e., the reflected or scattered radiated signal energy, is received by antenna  82  and passed electrically into a sampling receiver  86 . In the sampling receiver, the signal is “massaged” and digitized for processing, then passed into DSP 88 of digital signal processing system  34 . The processed data generated therein is passed to display  20  of display system  14 . While FIG. 3 shows only several basic elements of one embodiment of this invention, an actual Pipehawk system is fully integrated and autonomous. System operation is triggered from a signal generated in a wheel sensor to ensure that measurements are made in a regular and repeatable grid. All input or raw data is automatically stored in memory storage and processed by DSP 88. 
     Digital signal processing system  34  uses a collection of scans implemented by the antenna module  36  to determine if a an object, e.g., buried pipe, is located in a site (as well as its depth). FIG. 8 broadly depicts an object (pipe) detection process of this invention, beginning with a first step, represented by block  200 , in which raw data from the ground-reflected signal is collected within in a DSP 88 of DSP system  34 , said raw data transferred in from antenna module  36 . Block  202  represents a second step by which SAR processing and/or a migration operation is performed on the data within the DSP board. Block  204  represents a step of repeated SAR and/or migration procedure performed on raw data. Block  206  represents a step of mapping the processed (migrated) data. Block  208  represents a result, i.e., layers, of repetitive scanning. Block  210  represents a step wherein the DSP board performs a Hough transform on the then-processed data. Finally, block  212  represents a delivery of the processed data in a recognizable form to the user, i.e., put up on display  20  within display system  16 . 
     The characteristic hyperbolic response produced by underground objects detected in the reflected signal received at antenna  82  by the Pipehawk system  10  changes with depth, as well as changes of the dielectric constant of the soil with depth. The curvature of the hyperbola-like database are known to decrease with depth, however, said data are also found to decrease, independently of depth, with decreasing dielectric constant. Concomitantly, the shape of the hyperbola changes with depth and with changing dielectric constant. For that matter, the curvature of the hyperbolic representation of the object increases with increasing dielectric constant, as clearly described by FIG.  4 . It has been found, however, in testing performed on a prototype Pipehawk system, that any variation in dielectric constant with depth that occurs during measurement is very small and gradual. Accordingly, variations in dielectric constant can be assumed to be zero, or mathematically modeled to be incorporated into the processing to compensate for any changes in dielectric constant that occur. The unique processing which takes advantage of this knowledge to determine the correct dielectric constant is referred to as super-SAR. 
     The digital signal processor system  34  is controlled to perform specific DSP tasks, such as the SAR and/or super-SAR processing described below, on raw data received from the antenna module  36 . In particular, the DSP system  34  transforms the hyperbolic point-object data from its raw form to that which can be communicated via the display system  16 , i.e., in accordance with the softkey processing. The DSP system  34  performs a number of digital signal processing and filtering techniques, including Hough transformations, which may be referred to herein as synthetic aperture RADAR (SAR) processing in one embodiment, and super-SAR processing in another embodiment. For example, a line in image space of FIG. 5 (hyperbolic data) may be transformed to a point in the parameter or accumulator space after processing (FIG.  6 ). As shown in the figures, ρ=xcos v+ycos v, where x, y represent a point on the line, and v varies form 0 to π. 
     The system has a set of expected responses from a buried object for different depths (“buckets”) for different dielectric constants which are memory stored. When a scan is taken, the raw data are processed using the expected responses to find the closest dielectric constant matching that of the soil. A first pass is required to process the raw data using a wide range of dielectric constants to determine a narrower range for use in a second pass. In the second pass, using the narrower range, the processing selects the best matching dielectric. 
     FIGS. 9A and 9B together simplistically represent of how the synthetic aperture RADAR (SAR) technique correlates a set of point-object generated hyperbolic data with raw data, the method of which was discussed with reference to FIG.  8 . The SAR process essentially compares the hyperbolae. The correlation results is a measure of the similarity of the two hyperbolae. This essentially focuses the hyperbolae to a single point at which the target actually lies. Each correlation result is added by the signal processing for each focused point, resulting in a set of peaks with differing values. SAR techniques correlate all the stored hyperbolae with the raw data and adds the results, providing a diffused image of the object. Each correlation result is added for each focused point, resulting in a set of peaks for differing values. The set of points is used to show the data as a set of objects found by the scan (as shown in FIG.  4 A. The method generates noise around the targets, however, and therefore provides a badly focused image. The noise is due to the inability to isolate and use the dielectric constant of the soil. 
     The SUPER SAR technique implemented herein improves badly focused images (containing a lot of noise) typical with conventional SAR processing. Isolating and using the dielectric constant of the soil virtually eliminates noise such that target depth is accurately determined. While developing the “new” SAR technique, or SUPER SAR, it was found that any variation in dielectric constant with depth that occurs within a scan is small and gradual such that a single dielectric constant is used throughout the whole process. The SUPER SAR processing consists of the following steps, where ε n  is the n th  dielectric constant for the set of responses: 
     The raw data from the received portion of the radiated signal are first correlated for the dielectric constant, ε 1 , for a first bucket (bucket 1); second, bucket  1  is extracted and the result is memory-stored; third, the process is repeated for ε 1  for each of seven (7) buckets; and fourth, the migrated image, the result from the extraction of the seven buckets, is memory-stored. The above four steps are then repeated for a wide range of dielectric constants, ε N . A range of dielectric constants in which the best correlation is achieved is then selected. The complete process is then repeated for a narrower range containing the previous best range. This is essentially a process of converging onto the closest matching dielectric constant within the set of stored dielectric constants. Next the optimum dielectric constant, ε opt , from that range is selected. The data are then processed for optimal ε opt . (FIG. 4C represents the method). 
     Once all of the super-SAR processing is completed, the scans are sectioned horizontally to produce a map of the detected targets. The scans are split into seven (7) layers, where each layer displays the points located on each span for each target, as shown in FIG.  7 . Once all the scans are split into layers, Hough processing may be performed on each layer to identify any set of points in the layer. If such a feature exists, a line is drawn through the set of points, possibly identifying a pipe. 
     In theory, an unmigrated image consists of 512 possible hyperbola. However, the processing implemented herein can accomplish all hyperbola detection using only twenty memory-stored templates. To do so, one of the processing system&#39;s unique processing templates is used to generate a layer or “depth bucket” in the final image, as shown in FIGS. 10,  11  and  12 . FIG. 10 shows the depth bucket, FIG. 11 shows the corresponding hyperbolas and FIG. 12 shows the reference. The mean of the hyperbolas used in the template is the mean of the hyperbolas caused by objects in the depth bucket. As can be anticipated from the latter three figures (where dz is 25 points), hyperbola B will correlate well with hyperbolas C and A and can therefore be used to focus targets A, B and C. 
     Two dimensional correlation is depicted by the sequence of FIGS. 13,  14 ,  15  and  16 . Multiple target detection is depicted by the sequence shown in FIGS. 17,  18 ,  19  and  20 . By stacking each layer, an image of the full scan is generated (FIG.  21 ). If the time record at each acquisition point is 512 samples, then, in principle, the migrated image can comprise 512 layers. If a target has been detected in layer “n”, the data can be used to determine the correct dielectric constant of the burying matrix. The process consists of focusing layer n using a range of different dielectric constants, such as that described above. For each resulting layer, the target is located and its amplitude is measured, as depicted in FIG. 22. A plot of normalized amplitude against dielectric constant (ER) reveals the correct dielectric constant (FIG.  23 ). FIGS. 24 and 25 represent a preferred method of cluster processing as depicted by the blocks of FIG.  9 . 
     A physical implementation of the first preferred embodiment of the ground-probing RADAR system  300  (or Pipehawk), is depicted in FIGS. 26,  27 ,  28  and  29 , which show, respectively, a bottom plan view, a side plan view and a top plan view of the invention. The structure of the Pipehawk system of FIGS. 26-28 is shown to embody a ruggedly constructed cart  302 , a main body  304  of which includes a one-piece rotational housing  306 , preferably brightly colored for high visibility in a street environment. The rotational housing  306  houses the system&#39;s electronics, an LCD display  308  (preferably transflective) and a control panel  310 . Wheels  312 , a handle  314  for pushing the Piephawk system and an antenna module  316  are also mounted on the rotational housing. The Pipehawk system is also envisioned to be embodied in a motorized and remote-controlled cart, which can be programmed to cover a specified area without need for human interaction. 
     The antenna module  316  is mounted to the housing  306  by a compliant hinge that allows, within limits, the variations in the inclination of the ground to be accommodated in both axes. This allows the system  300  to cope with various cambers and gradients encountered in the street environment. The housing  306  is mounted on wheels  312  fitted with tires, preferably pneumatic. Correctly inflated tires are counted on to limit magnitude of shock transmitted to the electronics housed within the housing as the system is pushed forward. The interval at which measurements are recorded by a wheel sensor is approximately 50 mm, but may be varied in accordance with varying application according to those skilled in the art. 
     Preferably, the handle  314  is tubular, and is attached to the housing  306  to allow folding during transport. A number of positions are provided, preferably, by a series of castellations in the housing. A back face of the housing may comprise sheet metal. A bottom section of the housing houses a battery, accessible to the user. Above the battery compartment is a vent for exhaust of cooling air. Between the vent and display are two push-button switches for powering the system. Two connectors are provided proximate to the switches to allow power hook-up to charge the battery and download/transmit data. 
     Extensive thermal management is built in to the embodiment of FIGS. 26,  27 ,  28  and  29 . A prototype of the system has been tested operating in a range from around 0° C. to 40° C. Thermal control is achieved by providing two air circuits as shown in FIG.  29 . Within the main electronics module, fans are provided that stir the internal air, but the module is completely sealed. Extensive thermal transfer fins are provided on both the internal and external face of the module in order to transfer heat to external air. An external air circuit is provided that draws in air from above the antennas, passes around the electronics module and back of the display before being exhausted through the back panel. While air flow is temperature controlled, there is no filtering performed on the external air. 
     For optimum operation, the radar&#39;s antenna must be in contact with the ground (to minimize reflections). To that end, the antenna module is fitted with a sacrificial wear membrane to prevent the bottom face of its antenna from being worn. The antenna module includes a receiver and transmitter. The sacrificial membrane is replaceable. The transmitter is controlled to operate only when the system is actually being pushed along in the measurement mode (to be discussed in greater detail below). To obtain effective data, the antenna should be resting on the ground so the energy is coupled directly into the subsurface environment as maximum efficiency. 
     The housing is designed such that almost all the power of the radiated pulse signal is coupled directly to the ground, with only a small amount escaping into the surrounding air. The transmitter generates a fast risetime electromagnetic pulse signal with a time constant (r) of around one nanosecond (1×10 −9  second). The peak amplitude of the pulse signal is around 50V, but less than the signals fill energy is radiated. The pulse signal is scattered by changes in the electrical properties of the ground. The scattering produced by changes in ground conditions, returns a small fraction of energy back to the radar. FIG. 30 is a general schematic diagram of the radar part of the embodiment shown in FIGS. 26,  27  and  28  with a pulse generator acting as a transmitter, feeding a signal to the antenna to be introduced into the ground. The reflected (returned) signal is received and passed to digital signal processing hardware for massaging into suitable position for display. 
     Any embodiment of this invention may also be fitted with a data connector on any accessible panel, e.g., a back panel, which enables connections to be made either to an external computer, such as that controlling a cad/cam system for outputting accurate diagrams of the mapped underground, or to a printer directly. For example, the Pipehawk is fitted with three separate connectors. The first is a multi-way bayonet type connector, which meets military standards. From the main connector, two short cables extend in a branch, where on terminates with a keyboard connector for service activities and the other terminates with a standard D-type parallel connector for printing applications. In addition, an embodiment is envisioned which includes a separate transmitter and antenna section for transmitting processed display data to a receiver connected to a computer or like device, or a display and operator at a remote location. 
     FIG. 30 is a schematic block diagram showing interconnection of the Pipehawk system  300  functional interconnection. FIG. 30 includes antenna module  340  electrically connected to electronics module  361 . Electronics module  362  is also electrically connected to display module  370 , rear panel module  390 , battery module  398 , reset panel  391 , cooling fan module  400  and wheel sensor module  400 . 
     FIGS. 31A and 31B together show the structure of a delay coil (implementable as any of elements  344 ,  342 ,  342 ′,  348 ) for use herein as part of the antenna module  340 . The delay coils are used to implement a time delay for use in the transmit/receive pulse signal blanking cycles. FIGS. 32A,  32 B and  32 C show one embodiment of an antenna feed element which can be used herein. FIGS. 33A,  33 B and  33 C depict a connector assembly which can be used herein. FIGS.  34 A and  34 B together depict the element structure and layout for one embodiment of a two-element array as used herein. FIGS. 35A,  35 B,  35 C,  35 D and  35 A show mounting and feed elements which can be used herein. FIGS. 36A,  36 B,  38 A,  37 B,  37 C,  38 A,  38 B,  38 C and  38 D show various hardware elements which may be used. FIGS. 40A,  40 B,  40 C,  40 D,  40 E, and  40 F, and, FIGS. 41A,  41 B,  41 C and  41 D show various hardware elements for use herein, in conjunction with Table A. 
     While the Pipehawk system is a single channel ground probing RADAR system which is capable of detecting underground objects, the system must make numerous scans to assure large enough signal to noise ratios for accurate detection decisions. In order to increase productivity, a second preferred embodiment of this invention includes a two-channel RADAR system (referred to interchangeably as “the upgraded system”) capable of operating four data channels. Accordingly, a two-channel RADAR system  500  will now be described in accordance with FIGS. 42-48. FIG. 42 is a flow block diagram of the two-channel RADAR system&#39;s internal bus architecture. 
     The two-channel system  500  solves the problem of the need for taking more measurements for increased performance in a complicated underground environment. Cross-channel information is generated thereby, which is difficult to interpret in isolation, but useful in resolving ambiguities that occur in co-channel information. Co-channel data provides an initial model, subsequently aided by cross-channel data. Accordingly, the two-channel system operates four channels, including two antenna modules, two transmitters and two receivers. Each transmitter is used in turn send out a transmit signal, and both receivers are used to receive the reflected transmit signal; four channels are relayed thereby: Tx 1 Rx 1, Tx 1 Rx 2, Tx 2 Rx 2 and Tx 2 Rx 1, which will be referred to interchangeably as RADAR channels 1, 2, 3 and 4, respectively. The thus-described four RADAR channels essentially comprise the same four system blocks, RADAR A/D  502 , digital signal processor (DSP)  504 , a microprocessor  506 , and a tape unit  508 . The RADAR A/Ds are electrically connected to the transmitters/receivers, not shown explicitly in FIG.  42 . Each RADAR A/D  502  is also electrically connected in parallel to the DSPs  504  for parallel data transfer therebetween. The DSP data is also transferred in parallel between the microprocessors  506 . Each DSP  504  is also connected to a serial time division multiplexed bus for communication with a fifth DSP  504 . A fifth microprocessor  506  takes processed data and places it on display  510  for operator access. 
     The measurement geometry that evolved for this work consists of two antennae mounted on a single shaft (not shown in FIG. 42) and rotated to sweep over the areas of interest. A platform, the structure of which may be provided by one skilled in the art to meet application needs, is caused to advance as the antennae rotate the search pattern of the ground, as shown in FIG.  44 . FIG. 45 shows a prototype of the two-channel RADAR system  500 , i.e., the upgraded system. FIGS. 45A and 45B show search patterns for a search performed on the upgraded system mounted within a non-rotarized platform, which required that antennae be alternately rotated and moved forward. As can be seen in FIGS. 45A and 45B, by changing the ratio of forward to rotational movement, the density of measurement points may be changed. The platform (or “rig”) of FIG. 44 was arranged such that the antennae were set for a radius of 0.8 m and fifty measurement points corresponded to 180° of rotation. Two sets of scans were collected, one corresponding to the forward sweep of the rig and one to the rear sweep, thereby collecting full-circle data. 
     The analysis of data generated when the two-channel RADAR system runs along an object is simple. Applications of the SAR processing technique (in the DSP) with automatic depth calibration leads to a position of an object determined, and further analysis generates an angle of rotation corresponding to the center of the object. From the angle and radius of rotating the offset of the object relative to the center line of the measurement platform can be determined. If this is represented by X f  for the front scan and X r  for the rear scan, then the average position of the object relative to the rig is determined from the average of the two, and the rate of change of position along the length from the difference. 
     It is these two parameters, the average of the front X f  and rear X r  scans, and their difference which allows the unique processing function to be performed. The control method is based on a second order differential equation with two parameters differentially connected: position and rate of change of position. Accordingly, the processing allows for the data to be extrapolated such that a “k-space” analysis can be realized, thereby synthesizing many alternative measurement lines through the measurement space. As such, detection margins are increased to provide better spatial resolution in dense-pipe environments. By motorizing the structural rig which carries the system, with, for example, a stepper, the search pattern is placed under correlated software control. 
     In a variation on the Pipehawk system embodiment, a hand-held version of the Pipehawk II system  520  is shown in FIG. 47A and 47B. The system  520  includes a handle grip  522  for user handling and communication and power connection ports  524 . The system also includes a fold-away color display  526  and detachable antennae unit  528  which incorporates a motion sensor (not shown in FIG.  47 B). The Pipehawk II system  520  is also shown therein to include in housing  523  a concealed operator interface  570  which is accessible with display raised, a standard sampling receiver  532 , a standard pulse generator  534  and a standard baluns  536 , all shown in FIG.  48 A. FIGS. 48B and 48C identify location of repackaged electronics, which utilize standard STS formal circuit boards. 
     FIG. 49 is a flow diagram describing some of the DSP processing implemented by the present invention. FIG. 50 is an electrical schematic diagram of sampling circuitry for use herein, with FIGS. 51A and 51B shows electrical schematic diagrams of the sampling circuitry. FIG. 52 is a copy of a picture of a prototype of the Pipehawk invention which highlights the backplane; FIG. 53 is a copy of a picture which highlights the data port and power connection; FIG. 54 is a copy of a picture which highlights the housing; FIG. 55 is a copy of a picture which highlights the system&#39;s heat dissipation ability; FIG. 56 is a copy of a picture which highlights the system&#39;s display; FIGS. 57 and 58 are copies of pictures of a prototype of the Pipehawk invention which highlights the complete housing. 
     FIGS. 59A and 59B are schematic flow diagrams which together define one embodiment of the super-SAR processing implemented herein. The sampling receiver includes sampling and hold and amplifier circuitry for processing within a bandwidth range of 1.8 to 3 gigahertz. The circuitry highlights a GaAs sampling bridge, and fast slope recovery diodes, as disclosed in FIGS. 50,  51 A and  51 B. 
     What has been described herein is merely descriptive of the preferred embodiments of this invention. The description is not meant to, and should not be interpreted as, limiting the scope or spirit thereof 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE A 
               
             
             
               
                   
               
               
                 COORDINATE HOLE / FORM DATA 
               
             
          
           
               
                 REF 
                 SIZE / DESCRIPTION 
                 X DM 
                 Y DM 
                 Z DM 
               
               
                   
               
             
          
           
               
                 A1 
                 THREAD M3 
                 3.50 
                 3.50 
                 0.00 
               
               
                 A2 
                 THREAD M3 
                 7.00 
                 21.00 
                 0.00 
               
               
                 A3 
                 THREAD M3 
                 7.00 
                 81.00 
                 0.00 
               
               
                 A4 
                 THREAD M3 
                 3.50 
                 90.00 
                 0.00 
               
               
                 A5 
                 THREAD M3 
                 7.00 
                 159.00 
                 0.00 
               
               
                 A6 
                 THREAD M3 
                 3.50 
                 176.50 
                 0.00 
               
               
                 A7 
                 THREAD M3 
                 66.50 
                 176.50 
                 0.00 
               
               
                 A8 
                 THREAD M3 
                 63.00 
                 159.00 
                 0.00 
               
               
                 A9 
                 THREAD M3 
                 66.50 
                 90.00 
                 0.00 
               
               
                 A10 
                 THREAD M3 
                 63.00 
                 81.00 
                 0.00 
               
               
                 A11 
                 THREAD M3 
                 63.00 
                 21.00 
                 0.00 
               
               
                 A12 
                 THREAD M3 
                 66.50 
                 3.50 
                 0.00 
               
               
                 B1 
                 THREAD M4 
                 3.50 
                 12.00 
                 0.00 
               
               
                 B2 
                 THREAD M4 
                 3.50 
                 168.00 
                 0.00 
               
               
                 B3 
                 THREAD M4 
                 66.50 
                 168.00 
                 0.00 
               
               
                 B4 
                 THREAD M4 
                 66.50 
                 12.00 
                 0.00 
               
               
                 C1 
                 FORM RADIUS 4.0 
                 11.00 
                 7.00 
                 0.00 
               
               
                 C2 
                 FORM RADIUS 4.0 
                 11.00 
                 14.07 
                 0.00 
               
               
                 C3 
                 FORM RADIUS 4.0 
                 7.00 
                 18.63 
                 0.00 
               
               
                 C4 
                 FORM RADIUS 4.0 
                 7.00 
                 29.00 
                 0.00 
               
               
                 C5 
                 FORM RADIUS 4.0 
                 7.00 
                 73.00 
                 0.00 
               
               
                 C6 
                 FORM RADIUS 4.0 
                 7.00 
                 83.07 
                 0.00 
               
               
                 C7 
                 FORM RADIUS 4.0 
                 11.00 
                 87.93 
                 0.00 
               
               
                 C8 
                 FORM RADIUS 4.0 
                 7.00 
                 96.93 
                 0.00 
               
               
                 C9 
                 FORM RADIUS 4.0 
                 7.00 
                 151.00 
                 0.00 
               
               
                 C10 
                 FORM RADIUS 4.0 
                 7.00 
                 161.37 
                 0.00 
               
               
                 C11 
                 FORM RADIUS 4.0 
                 11.00 
                 165.93 
                 0.00 
               
               
                 C12 
                 FORM RADIUS 4.0 
                 11.00 
                 173.00 
                 0.00 
               
               
                 C13 
                 FORM RADIUS 4.0 
                 59.00 
                 173.00 
                 0.00 
               
               
                 C14 
                 FORM RADIUS 4.0 
                 59.00 
                 165.93 
                 0.00 
               
               
                 C15 
                 FORM RADIUS 4.0 
                 63.00 
                 161.37 
                 0.00 
               
               
                 C16 
                 FORM RADIUS 4.0 
                 63.00 
                 151.00 
                 0.00 
               
               
                 C17 
                 FORM RADIUS 4.0 
                 63.00 
                 96.93 
                 0.00 
               
               
                 C18 
                 FORM RADIUS 4.0 
                 59.00 
                 87.93 
                 0.00 
               
               
                 C19 
                 FORM RADIUS 4.0 
                 63.00 
                 83.07 
                 0.00 
               
               
                 C20 
                 FORM RADIUS 4.0 
                 63.00 
                 73.00 
                 0.00 
               
               
                 C21 
                 FORM RADIUS 4.0 
                 63.00 
                 29.00 
                 0.00 
               
               
                 C22 
                 FORM RADIUS 4.0 
                 63.00 
                 18.63 
                 0.00 
               
               
                 C23 
                 FORM RADIUS 4.0 
                 59.00 
                 14.07 
                 0.00 
               
               
                 C24 
                 FORM RADIUS 4.0 
                 59.00 
                 7.00 
                 0.00 
               
               
                 D1 
                 HOLE GROUP SEE DETAIL 
                 0.00 
                 51.00 
                 33.55 
               
               
                 D2 
                 HOLE GROUP SEE DETAIL 
                 0.00 
                 128.00 
                 33.55 
               
               
                 E1 
                 HOLE GROUP SEE DETAIL 
                 0.00 
                 51.00 
                 13.70 
               
               
                 F1 
                 SLOT DETAIL 
                 7.00 
                 38.25 
                 0.00 
               
               
                 F1 
                 SLOT DETAIL 
                 7.00 
                 63.75 
                 0.00