Abstract:
The present invention teaches a variety of mechanisms, techniques and systems for managing, labeling, detecting, locating, and utilizing Hidden Objects utilizing RFID technology, handheld data processing units, and a centralized server computer maintaining a database of information related to a plurality of Hidden Objects. The teaching of the present invention has application across a wide variety of industries including constructions, utility, governmental, military, waste water management, etc.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to U.S. Provisional Patent Application No. 60/630,835, entitled, “Detecting, Locating and Managing Hidden Objects Using RFID Technology, and which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates generally to the field of detecting and locating hidden objects or assets located underground, above the ground or concealed in walls or other structures. More specifically, the present invention teaches a variety of systems and methods utilizing radio frequency identification (RFID) technology for labeling, detecting, mapping, locating, tracking, maintaining, and managing hidden assets of any type.  
       DESCRIPTION OF PRIOR ART  
       [0003]     Electrical, telecommunciations (fiber-optic and copper), oil, gas, water supply (drinking and industrial water), wastewater, chemical, air conditioning and other utility lines or pipes, PINS used as location identifiers for surveying and more are often placed under the ground or in between the walls of erected structures. They may also be above the ground but over time become hidden because of vegetation or other such covering. This covering is often for ergonomic, safety and cost reasons. In addition to lines and pipes, storage tanks and vessels are also kept under the ground. Also wooden beams and other such structures are often placed between the walls in houses and other erected structures. All these are referred to as “Hidden Objects.” 
         [0004]     The use of Hidden Objects occurs in a wide variety of industries including utility companies, manufacturing plants and facilities, government, construction industry, hospitals, airports, gas stations, private and commercial properties, real-estate industry, research labs, universities, cities, municipalities, oil and gas industry and more. All these are collectively referred to as “User Companies.” 
         [0005]     It is important to know the exact location of the Hidden Objects when repair and additions are made to industrial and urban structures, or whenever activity is occurring around such Hidden Objects. Unfortunately, time and again, the exact location of these objects deviate from “as-built” drawings, if the latter exists, design drawings and other mechanisms used to collect location data. As a result, when repair services or additions to facilities require construction in the vicinity of these lines, the construction runs into unanticipated problems such as breakage, re-routing, and delays. In order to perform cost effective detection of such underground objects and objects concealed in and around erected structures and potential construction sites, it is essential that the presence, location and depth of such lines be accurately determined. Locating these Hidden Object using available techniques is costly and ineffective.  
         [0006]     Existing techniques for detecting underground assets include the use of technologies such as GPR (ground penetrating radar). However, GPR based systems generate large amounts of unnecessary data, data that is non-specific or non-descriptive of the location and line identified, and therefore results in inaccuracies and a lower level of specifiable detail about the object. GPR tends to be unable to distinguish between the signals returned by an underground object of interest from that of the signals returned by other sub-surface objects.  
         [0007]     GPS is also used to locate assets. In this case, existing maps are digitized and the data is stored in a database. This data is accessed using a GPS enabled handheld device on the field to locate the assets. However, the problems with this approach are many. The accuracy of most GPS devices is 3 to 5 m unless Differential GPS (DGPS) is used which requires extensive processing time and is expensive. Given this margin of error, locations identified with GPS also lack in repeatability. Additionally, GPS requires line of sight with satellites and does not function properly in shades of trees, buildings etc.  
         [0008]     Sometimes metal detectors are used in addition to GPS to locate Hidden Objects. Metal detectors have problems such as failing to distinguish between a metallic utility line and another piece of metal that is adjacent to it.  
         [0009]     What is needed is an accurate, cost efficient system and method for labeling, detecting, mapping, locating, tracking, maintaining, monitoring, protecting and managing the Hidden Objects.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  diagrammatically illustrates an RFID based location identifier (RFIDLI).  
         [0011]      FIG. 2  shows two RFID based Location Identifiers and an underground utility line (Hidden Object) in a plot of open land.  
         [0012]      FIG. 2   a  shows a plot of open land that has an underground utility line and RFIDLIs that are placed on the surface, directly above the utility line to label and track (or locate) the utility line.  
         [0013]      FIG. 2   b  shows a cross section of the plot of land shown in  FIG. 2   a  indicating that the RFIDLI is directly above the utility line and above the ground.  
         [0014]      FIG. 2   c  shows an underground utility line and 4 RFIDLIs in an open plot of land. The RFIDLIs are placed in the vicinity of the underground line, but not directly above it.  
         [0015]      FIG. 3  shows Hidden Objects in a wall.  
         [0016]      FIG. 4  shows a horizontal area that could be a plot of land or other horizontal structure (e.g., cemented floor) with 3 Hidden Objects.  
         [0017]      FIG. 5  represents an RFID Reference Tree showing the relationships between the Root Node RFIDLI, Intermediate Node RFIDLIs and Starting RFIDLIs.  
         [0018]      FIG. 6 a  system according to one embodiment of the invention.  
     
    
     SUMMARY OF THE INVENTION  
       [0019]     The present invention includes teachings directed to the identification of Hidden Objects using an integrated hardware and software system that uses RFID technology. According to one embodiment, RFID based Location Identifiers are placed in the vicinity of a Hidden Object. “In the vicinity” of a Hidden Object means on the Hidden Object, directly above the Hidden Object, on the surface of the Hidden Object, adjacent to the Hidden Object, etc. The data stored in the RFID tags of these RFIDLIs is read using a Handheld Data Processing Unit (HDPU) and is processed further to identify and determine location information for the Hidden Object, such as the co-ordinates, depth below the surface of the ground or depth from the surface and width at different points or locations of the Hidden Object.  
         [0020]     This invention also teaches the development of a Location Based Master Database identified through RFIDLIs for different User Companies including the information on the Hidden Objects, location data of the Hidden Object and make, parts, installation/repair information, maintenance history and more, by locations. The data for different User Companies may be shared by each User Company with partners, customers and more  
         [0021]     This invention is also directed to using the information accessed from the database, using the RFIDLIs as reference points, for maintenance purposes. This will allow a User Company to develop a maintenance history database to perform efficient maintenance.  
       DETAILED DESCRIPTION OF EMBODIMENTS  
       [0022]     The present invention teaches a variety of techniques and mechanisms that enable labeling, tracking, locating, maintaining, and managing Hidden Objects using an integrated hardware and software system that uses RFID technology.  
         [0023]     The use of RFID based location identifiers (RFIDLI) as reference markers for storing critical information regarding the Hidden Objects is an attractive solution that can be used to accurately label, track, locate, maintain and manage the Hidden Objects. Certain embodiments of the present invention will save time and dollars during repairs and construction in industrial and urban facilities, and may also help crews locate the lines in the event that they want to make upgrades to existing facilities or add new facilities.  
         [0024]     The invention will also help in monitoring and maintenance of a Hidden Object (and its contents) for better security and efficiency. In addition to the User Companies, this invention can also be extended to general surveys done by survey companies; demarcation of property boundaries, right of ways, etc; and as a general tool for homeowners to locate and delineate features that are important to them.  
         [0025]     The present invention uses RFIDLI s, Handheld Data Processing Units (HDPU) and a Server (see  FIG. 6 ). The HDPU unit runs the Handheld Software (h-sw) while the Server runs the Server Software (s-sw). As will be appreciated, the Server may comprise one or more computers and other computer hardware. The HDPU unit is comprised of an RFID Reader (or Readers) and a Handheld device (HD) such as a PocketPC, PDA or smart phone. If the HD does not have GPS receive capability, according to some embodiments the HDPU will include a GPS receiver. The Server, although of great use in certain embodiments, is not always necessary in every embodiment.  
         [0026]     Data on the RFIDLIs and Hidden Objects may be stored on the Server (if it is used) and/or the HD. The HD communicates with the Server wirelessly in real-time or is synchronized to the Server (or via a PC, etc.). The discussion below assumes the use of a Server that communicates with the HD to send and receive data using a wireless connection. Those skilled in the art will readily recognize how a synchronized system or other model might operate given the teaching herein.  
         [0027]     A Hidden Object&#39;s Location Data Set may be defined as the set of Location Data at multiple different Location Points along the layout of the Hidden Object. A Location Point is a point on the Hidden Object. Location Data can take the form of various suitable attributes such as X-Y co-ordinates, distance and angle (D, A), GPS coordinates (Latitude and Longitude, or Northing and Easting), elevation of ground at Hidden Object, Depth and Width of the Hidden Object at a particular Location Point and more. X-Y co-ordinates are relative co-ordinates (i.e., relative to a reference point X=0, Y=0).  
         [0028]     In the case of (D, A), the distance D is the distance of the Location Point from the reference point R 1  ( 20  in  FIG. 2 ) and the angle A is the angle between the line joining the reference point R 1  to a second reference point R 2  ( 21  in  FIG. 2 ) and the reference point R 1  to the location point ( FIG. 2 ). The Depth at that Location Point typically may be locally relative (e.g., the depth of the Hidden Object below the ground surface if the object is underground or from a known local surface if the objects is concealed in a wall or other such structure) or locally absolute (e.g., a measurement with respect to some fixed point such as sea level). The Width refers to the width of the Hidden Object at that Location Point.  
         [0029]     Similarly, an RFIDLI is also identified by Location Data, which includes similar attributes as required.  
         [0030]      FIG. 1  is a diagrammatic view of an RFIDLI  10 . The RFIDLI  10  includes an RFID tag  12  that is surrounded by an optional protective casing  14 . The Protective Casing  14  is formed of a material that tends to prevent the tag from getting damaged or exposed to water or any harmful material. The protective casing  14  also prevents the tags from coming in direct contact with metal surfaces or structures. As will be appreciated, metal may impair the detection of RFID tags, depending on the radio frequency used. Those skilled in the art will be well familiar with RFID tags. The material and manufacture of the protective casing  14  will depend upon the specific application, and will be readily apparent to those skilled in the art depending thereon.  
         [0031]     The RFID tag  12  may take any suitable form such as:  
         [0032]     Passive read-only or read-write. Passive tags do not require any battery and are activated by the radio frequency signal from the RFID Readers.  
         [0033]     Active read-only or read-write. Active tags are battery powered and therefore require replacing the battery when the battery runs out.  
         [0034]     Semi-active/semi-passive read-only or read-write. Semi-active tags have a battery but the usage of the battery is optimized such that it is mostly in sleep mode and wakes up to power the chip only when an RFID Reader tries to read the tag or write into it.  
         [0035]     Those skilled in the art will understand that active and semi-active/semi-passive tags have a much higher range than passive tags, and that the use of such technology depends upon application constraints.  
         [0036]     A read-write tag typically contains a unique identifier and non-volatile memory that can be written to and read from by using an RFID Reader. Therefore, the tag can be programmed with the desired information as demanded by the needs of the specific application.  
         [0037]     Read only tags can also be used to provide these solutions; in such implementations the unique identifier of the tag will be used to fetch the other information (that would be stored in non-volatile memory for a read-write tag) from storage on the Server.  
         [0038]     All the references to RFIDLIs in the rest of this document assume the use of active read only tags. Depending on the requirements of the specific implementation, it may be necessary to use any of the other types of tags from those mentioned above.  
         [0039]     The passive RFID tags can operate at different frequency ranges, one suitable frequency range being between 13.56 MHz and 2.45 GHz. Lower frequencies such as 13.56 MHz are better at penetrating dense medium and are not affected by metal or liquid based medium (the medium between the RFID tag and the Reader that reads the tag). However, 13.56 MHz technology may require the RFID Reader to have an antenna of several feet and also provides less range.  
         [0040]     In contrast, higher frequencies allow the desired antenna geometry of the RFID Reader (in HDPU) to be smaller and therefore are more convenient to use. 915 MHz allows for a smaller antenna and offer a good compromise over the 2.45 GHz tags that have poor penetration characteristics. Thus 13.56 MHz or 915 MHz tags are well suited in many situations, depending on the penetration characteristics, range and the size of the antenna desired.  
         [0041]     Some active tags use 868 Mhz or 916.5 Mhz as the operating or transmission frequency from the tag and 433 Mhz as the wake-up frequency. Those of skill in the art will be familiar that other frequencies that may also be used instead of these frequencies.  
         [0042]      FIG. 2   a  pictorially illustrates five RFIDLIs  42 ,  43 ,  44 ,  45  and  46 , in a certain physical area  40 . There maybe more RFIDLIs in the area  40 . Also shown is underground utility line  41 . The RFIDLIs are placed directly above Location Points on utility line  41 , on the surface above the ground. It is also possible to have the RFIDLIs placed underground, either attached to different points on utility line  41  or above it in the soil.  FIG. 2   b  shows a sectional blown up view of the RFIDLI  42  of  FIG. 2   a.    
         [0043]     To label utility line  41  using the RFIDLIs  42 ,  43 ,  44 ,  45  and  46 , place these RFIDLIs at different locations directly above the utility line  41 , on the surface. If  41  is an existing underground line, locate  41  using a map, metal detector or any other suitable mechanism and then place the RFIDLIs on it. If  41  is a new line, dispose the RFIDLIs as the line is put in place. Obtain the Location Data for the RFIDLIs using DGPS or any other suitable method, then collect this data along with the corresponding tag identifier of the RFIDLI in the Server database (the data is sent by HD to Server).  
         [0044]     To track (or locate) the Hidden Object, use the HDPU&#39;s GPS to arrive at the approximate location of interest. Alternately, if the HDPU does not have GPS capability, use a map or any other suitable mechanism such as using a known landmark as reference to arrive at the approximate location of interest (Current Location). Next, provide the Current Location as input to the h-sw on the HD to obtain the Location Data of nearby RFIDLIs. The h-sw should preferably have a GUI interface to provide the information conveniently and allow the data to be managed as the RFIDLIs are located.  
         [0045]     Continuing on with tracking, with this data use the RFID Reader to read, detect and then locate the RFIDLIs that are within the range of the Reader. Since active RFID tags can be detected from even 150 feet away and the range can be tuned or changed, progressively keep reducing the range to zoom into an RFIDLI. If using passive tags of about 10 ft range, visually locate the RFIDLI or Hidden Object once a reading is obtained. Once an RFIDLI is located, place a visual marker to label it. It is also possible to use a dual frequency RFIDLI where the RFIDLI includes an active tag (higher range) and a passive tag (typically 13.56 Mhz passive tag with a much lower range). In that case, the RFID Reader (s) would have the ability to read both the tags; first the active tag would be detected to find the vicinity of the dual frequency tag and then by zooming in once you are close to the tag use the lower frequency RFID Reader to read the passive tag (range &lt;1 m) and locate it.  
         [0046]     If an RFIDLI is lost, take two other RFIDLIs, consider one to be the Base and the other as the Reference. Now place a survey instrument on the Base and point to the Reference to obtain a reference reading. Then use the h-sw to obtain the angle of rotation from the Reference and the distance of the lost RFIDLI from the Base—provide these as input to the survey instrument to identify the location of the lost RFIDLI. If you repeat this using another set of RFIDLIs as Base and Reference RFIDLIs, you can reduce the margin of error due to the survey instrument and obtain an even more accurate reading.  
         [0047]     Also, note that once you have detected a few RFIDLIs in a certain area, certain embodiments of the present invention enable you to use the Location Data of a known (or detected) RFIDLI as a reference point to obtain other RFIDLIs that are in its vicinity. This way, during tracking (or locating) of a Hidden Object the only time you need a GPS is at the start.  
         [0048]     One can place RFIDLIs on valves, bends and other such points of interest and record the fact that the specific RFIDLI is on a valve (or bend etc.) in the Server database. This way, in addition to locating the underground asset from above the ground, you can also use the solution to locate valves, bends and more, easily and fast in the case of an emergency. Note, the valves can be above the ground.  
         [0049]     With reference to  FIG. 2 , we now describe how RFIDLIs can be used to track and locate a Hidden Object where the RFIDLIs are near the asset but not on or directly above it.  FIG. 2  pictorially illustrates three RFIDLIs  20 ,  21  and  22  that are placed at different locations in a certain physical area  25 . The area  25  refers to land that may belong to the government, private individual owners or commercial area. Also shown in  FIG. 2  are a utility line (Hidden Object) asset  30  disposed underground and a building  34  both found within the certain physical area  25 . RFIDLIs  21 ,  21  and  22  may be above the ground or under the ground; these may be three of a plurality of additional RFIDLIs disposed within the certain physical area  25 .  
         [0050]     To label the asset  30 , the Location Data Set of the asset  30  is obtained either from digitized maps or by collecting Differential GPS co-ordinates of different Location Points on asset  30  when it is installed. The Location Data Set of asset  30  is stored in the database on the Server. Next, when the RFIDLIs ( 20 ,  21  and  22 ) are placed at different locations in  25 , the Differential GPS co-ordinates are obtained for each RFIDLI. The data is collected via the HD and transmitted wirelessly to the Server for storage in the database.  
         [0051]     Alternately, instead of taking the Differential GPS readings for each of the Location Points on asset  30  or the RFIDLIs, it is also possible to get the Location Data for each of these Location Points on asset  30  and some of the RFIDLIs (Other RFIDLI) using one of the following:  
         [0052]     Relative-label Method 1: In this case, use two known RFIDLIs (whose co-ordinates are known), one as the Base RFIDLI ( 20 ) and the other as the Reference RFIDLI ( 21 ). Place a survey instrument on the Base RFIDLI and focus it on the Reference RFIDLI to get a reference traverse. Next, rotate the survey instrument to focus on a Location Point on asset  30  or Other RFIDLI to obtain it&#39;s location relative to the Base RFIDLI as angle (A) and distance (D). The angle is the angle by which the survey instrument needs to be rotated from the reference traverse to the Location Point on asset  30  or Other RFIDLI; the distance is the distance between the Base RFIDLI and the Location Point on asset  30  or Other RFIDLI. This data is converted and stored on the Server as absolute GPS co-ordinate.  
         [0053]     Relative-label Method 2: Use two known RFIDLIs (whose co-ordinates are known), one handheld laser and two prisms on bipods for this method. Place the bipods on the two known RFIDLIs (known co-ordinates), stand on the Location Point on the asset  30  or the Other RFIDLI (Label Location) whose co-ordinates are needed and shoot the laser back to the two prisms to obtain the distance to the two prisms. Using the Location Data of the two known RFIDLIs and the distances of the two RFIDLIs from the Label Location, the h-sw automatically calculates the Location Data of the Location Point on asset  30  or the Other RFIDLI.  
         [0054]     To track (locate) the asset  30 , first use the HD&#39;s GPS, a separate GPS device, a map or known landmark to arrive at the approximate location of interest. Then, input the current location into the h-sw of the HD to obtain the Location Data of nearby RFIDLIs (say  20  and  21 ). It is possible to channel the output of the GPS directly into the h-sw of the HD, to make it easy for the user to specify the current location.  
         [0055]     Next, use the RFID Reader to locate two RFIDLIs, one is referred to as the Base RFIDLI ( 20 ) and the other as the Reference RFIDLI ( 21 ). Place a survey instrument on  20  and focus it on  21  to calibrate it. Next, based on the Base ( 20 ) and Reference ( 21 ) RFIDLIs, obtain Location Data of different Location Points  31 ,  32  and  33  on asset  30  as angles and distances(D, A). Angle A represents the angle by which the survey instrument needs to be rotated from the Reference (from the reference-line joining  20  and  21  to the line from the Base  20  to the LP  31 ,  32  or  33 ) and distance represents the distance D of the Location Point ( 31 ,  32  or  33 ) from the Base RFIDLI  20 . This way the user may locate and mark each Location Point on asset  30 . To minimize the survey instrument&#39;s error, this process may be repeated again using a different Base RFIDLI ( 21 ) and Reference RFIDLI ( 22 ).  
         [0056]     In this method all Location Data for the RFIDLIs and the Location Data Set of the asset are stored as absolute co-ordinates. A user can arrive at a certain area, make one RFIDLI in that area as the Base RFIDLI and another as the Reference RFIDLI, and then follow the steps outlined above to locate the asset. It is also possible to store the Location Data of the asset and the RFIDLIs relative to a known reference point instead of as GPS co-ordinates.  
         [0057]     Another technique can be used for locating underground lines. This technique uses a handheld laser and two prisms on bipods, in addition to the components outlined in  FIG. 2 . In  FIG. 2   c , asset  81  is an underground utility line in an open plot of land  80 . Location Points  81 - 84  are on the asset  81  and RFIDLs  85 - 88  are placed in the vicinity of the asset  81 .  
         [0058]     After you locate two RFIDLIs ( 86  and  87 ) using the HDPU (as mentioned above for  FIG. 2 ), place the bipods on the RFIDLIs  86  and  87  (whose co-ordinates are known). The person locating the buried line stands at a point in the vicinity of the  86  and  87  and shoots the laser back to the prisms to obtain the distance to the two prisms. A triangle is plotted on the HD (h-sw) showing the location of the person, the location of a point of interest (Location Point) on the line (the point one is trying to locate). The HD provides the distance and the direction the person should move to be located directly on the point. The person relocates and re-shoots the distances. Once a point is located on the line  82 , adjacent points  83  and  84  along the trajectory are located similarly based on information provided through the HD.  
         [0059]     There is another possible implementation for  FIG. 2  where an RFIDLI is associated with a next and a previous RFIDLI as well as certain Location Points on the asset. In this case, corresponding to each RFIDLI (say  20 ), information that is stored (if using read only tags on the Server or, if using read-write tags, in the writeable area of the RFID tag) against the RFID tag identifier of the RFIDLI includes the following:  
         [0060]     Type of object that is been identified (power line, waste water line etc.). The object here is the utility line asset  30 .  
         [0061]     Ownership and other related information regarding the Hidden Object.  
         [0062]     The Location Data of the RFIDLI  20 .  
         [0063]     The Location Data for some of the Location Points in its vicinity say  31 ,  32  and  33 ; these are location points on the utility line asset  30 .  
         [0064]     The Location Data of the next RFIDLI  21 . If this is the Last RFIDLI, it&#39;s next RFIDLI is NULL.  
         [0065]     The Location Data of the previous RFIDLI (since this is the First RFIDLI, this would typically be NULL). First RFIDLI does not have a previous RFIDLI.  
         [0066]     As mentioned earlier, the Location Data for each of the above bullets can be absolute or relative to a reference point (could be the RFIDLI itself). Of course, the above list of information is merely one possible set of information that may be stored in each RFIDLI.  
         [0067]     In addition, other information such as when the RFIDLI was installed, a last time the RFIDL was read and other information may also be stored. In certain cases, information relating to curvature of utility line asset  30  may also be stored.  
         [0068]     If using read-write RFID tags some or all of the information may be stored in the RFID tags. If using read-only RFID tags, typically the only information that will be present at  20  and  21  will be the unique RFID tag identifier. In this case, all other relevant information that is mentioned above will be stored and fetched as needed from the Server, or HD, or perhaps provided manually by the user. If using this method, the Location Data Set of asset  30  is obtained from digitized maps, by collecting Differential GPS co-ordinates of different Location Points on asset  30  when installed, or by using Relative-label Method 1 or Relative-label Method 2. The user would then store the Location Data Set in the database on the Server, and next, place RFIDLIs at different locations in  25  and obtain their DGPS co-ordinates. Following that, use tools provided by the h-sw or s-sw to associate each RFIDLI with its next and previous RFIDLI and a set of Location Points of asset  30 . To locate, use a technique that is similar to the one outlined above ( FIG. 2  tracking Hidden Object).  
         [0069]      FIG. 3  illustrates a hidden object disposed in a structure and will be used to describe how the invention can be used to detect concealed objects in a wall or other non-horizontal structure. Often times, electrical, communication, plumbing, water, waste and other lines are present as concealed objects inside walls. Additionally there are other objects such as vertical beams (made of wood) that often need be detected externally for different purposes. This invention can be used to effectively detect all such concealed objects from outside, without damaging these objects by drilling.  
         [0070]      FIG. 3  illustrates a vertical structure  90 , like a wall, including concealed utility lines  70  and  80 . Utility lines  70  and  80  represent, for example, concealed utility lines (Hidden Objects) within a vertical wall in a manufacturing facility, warehouse or other commercial or residential property. On or in the vicinity of the vertical structure  90  are disposed three RFIDLIs  50 - 52 . There may be other such RFIDLIs disposed in the vicinity. Location Points  60 - 63  are disposed on utility line  70  and Location Points  64 - 69  are disposed on utility line  80 . Two possible solutions are described below as solution  3 A, where the Location Points are not RFIDLIs (or do not have RFIDLIs on them), and solution  3 B where the Location Points are also RFIDLIs.  
         [0071]     In the case of solution  3 A, RFIDLI  50  is used as the Base RFIDLI and RFIDLI  51  is used as the Reference RFIDLI. The Location Data of all the Location Points on a utility line are calculated relative to the Base RFIDLI (x=0, y=0, z=0). Here x=0, y=0 and z=0 is used for simplicity. It is possible to have the Base at x=x 1 , y=y 1  and z=z 1 , where x 1 , y 1  and z 1  may or may not be 0. The Location Data of RFIDLIs  51  and  52  are also calculated relative to RFIDLI  50 . To determine the Location Data of the different location points on utility lines  70  and  80 , one can use a simple tape or similar device to calculate the x, y and z co-ordinates of the Location Point from the Base RFIDLI  50 . Alternately, you can use a survey instrument like Total Station or Laser and with RFIDLI  50  as the Base RFIDLI and RFIDLI  51  as the Reference RFIDLI.  
         [0072]     Continuing on with the description of  FIG. 3A , place the survey instrument on the Base, focus it on the Reference to calibrate and then rotate it from the Reference to focus on a Location Point  61 . The survey instrument will tell you the angle of rotation and the distance from the base—(angle  1 , distance  1  for the X-Y plane and angle 2 , distance 2  for the X-Z plane); use these values to calculate the x, y and z co-ordinates of Location Point  61  relative to RFIDLI  50 . Enter the data in the h-sw of the HD and transmit for storage on the Server. Also, store information corresponding to utility lines  70  and  80  like the name of the Hidden Object, its type (electrical line, water line etc.), ownership information, install date, maintenance history and more.  
         [0073]     To locate a Hidden Object  70 , e.g., first arrive at and read the RFIDLI  50  (Base) using the RFID Reader. The information on the location of the RFIDLIs is obtained from the HD (h-sw) which communicates wirelessly with the server to obtain such information. Instead of RFIDLI  50 , any of the other RFIDLIs ( 51 ,  52  etc.) may also be used as Base. Next, make RFIDLI  51  the Reference RFIDLI. Place a survey instrument on the Base, focus it on RFIDLI  51  to calibrate it. Now, obtain the Location Data for different Location Points on the utility line  70  using the HD (h-sw) relative to the Base RFIDLI  50  and use the survey instrument to determine the locations of all the Location Points on utility line  70 , as described previously for locating Hidden Objects in  FIG. 2 . You can use a survey instrument like Total Station or Laser. Alternately, it may be also possible to locate the Location Points on utility line  70  using a simple measuring tape once you obtain the Location Data of the different Location Points relative to the Base RFIDLI (no Reference RFIDLI needed in this case).  
         [0074]     The other solution of  FIG. 3, 3   b , uses RFIDLI  50  as the Root Node RFIDLI while all the Location Points on the utility lines  70  and  80  are also RFIDLIs ( 60 ,  61 ,  62 , . . .  69 ). While it is preferable to implement this solution by storing all the data corresponding to RFIDLI&#39;s tag identifier on the Server in the database, it is possible to implement this solution using read-write tags for simplicity. In this case, it is better to use an active tag for  50  and passive 13.56 MHz or 915 MHz tags for the RFIDLIs that are on the utility lines  70  or  80 .  
         [0075]     The Root Node RFIDLI contains the Location Data of itself and the Location Data of Location Points  60  and  64 , the Starting RFIDLIs as co-ordinates relative to RFIDLI  50 , for the utility lines  70  and  80  respectively. Location Points  60  and  64 , the Starting RFIDLIs contain the Location Data of itself, the Location Data of the next RFIDLI ( 61  and  65  respectively) and the Location Data of its previous RFIDLI (NULL for Starting RFIDLIs). Similarly, all the other Location Points on utility lines  70  and  80  store information on their Location Data, the Location Data of the next RFIDLI and the Location Data of the previous RFIDLI.  
         [0076]     To label the assets  70  and  80  using this method, first place the RFIDLI  50  and store Location Data on the Server. Next to label a utility line  70 , place the Starting RFIDLI  60  on utility line  70 . Store the Location Data of RFIDLI  50 , the Location Data of Location Point  60  (and other Starting RFIDLIs) and other information on the writeable area of the RFIDLI  50 . Alternately, if using read only tags store all the data corresponding to the tag identifier of RFIDLI  50  on the Server. Similarly, in RFIDLI  60  store the Location Data of itself and the location data of the next RFIDLI  61  (since this is the Starting RFIDLI, the previous RFIDLI=NULL). Use this method to store data corresponding to each of the RFIDLIs  62  and  63 .  
         [0077]     To locate a line  70  using solution  3 B, first arrive at the vicinity of RFIDLI  50  and use the RFID Reader to read the tag and locate it. You will now have the Location Data for Location Point  60 . You can use a simple tape to mark the Location Point  60  using the data and then read the RFIDLI using an RFID Reader to obtain the co-ordinates of the next Location Point  61 . If you use read-write tags use the HD (h-sw) to view the tag data. Use this technique to read the other Location Points  61 ,  62  and  63 . Alternatively, it is possible to use a survey instrument as well.  
         [0078]      FIG. 3  represents a single wall or non-horizontal structure. Often, say in a commercial building or large manufacturing facility, you will have many walls and other structures with many Hidden Objects in each such structure. In addition, there will be underground Hidden Objects.  FIG. 5  outlines how you can start with a Root Node RFIDLI and locate all Hidden Objects using a reference tree  155 .  
         [0079]     In a case where there are multiple hidden objects, start with the Root Node RFIDLI  160 , read its Location Data to locate the Intermediate Node RFIDLIs  161  and  162  and the Starting RFIDLIs ( 170 ). The Intermediate RFIDLI  161  contains the information on the Starting RFIDLIs ( 172  and  173 ). It may also have information on other Intermediate Node RFIDLIs. Traverse down the tree to read the contents of the nodes to locate the Starting RFIDLIs, the starting point for each Hidden Object. Then use the mechanism described with reference to solution  3 B above to locate the entire Hidden Object. If using solution  3 A, instead of Starting RFIDLI the Root or an Intermediate RFIDLI will point to a Base RFIDLI which will have a Reference RFIDLI as the leaf node. The RFIDLIs mentioned in  FIG. 5  can be implemented using either Read only tags or read-write tags.  
         [0080]     For example, Root Node RFIDLI  160  may contain:  
         [0081]     Unique RFID identifier  
         [0082]     Company, ownership and other reference information as needed  
         [0083]     The Location Data for itself ( 160 )  
         [0084]     Location Data for the Intermediate RFIDLIs and the Starting RFIDLIs (or Base RFIDLI) that form its immediate child nodes.  
         [0085]     In  FIGS. 5, 161  and  162  are Intermediate RFIDLIs while  170  represents a Starting RFIDLI. The Reference Tree  155  shown in  FIG. 5  can be of any depth, depending on the complexity of the structure and the locations of the Hidden Objects.  
         [0086]     Similar to  FIG. 3 ,  FIG. 4  shows how objects that are underground and other areas where GPS does not work (e.g., inside a building) or is unavailable may be located. As in the case of  FIG. 3 , in this case also there are 2 possible solutions  4 A and  4 B which are similar to solutions  3 A and  3 B respectively. In the case of solution  4 A, we use a Base RFIDLI and a Reference RFIDLI to locate different Location Points on the utility lines  110 ,  120  or asset  30 . In  FIGS. 4, 150 ,  151  and  152  are all RFIDLIs and any of these can be used as Base or Reference RFIDLIs. In the case of solution  4 B, we use RFIDLI  150  as a Root Node RFIDLI and use it to locate the Starting RFIDLIs  140 ,  141  and  142 . Next, use a method similar to solution  3 B to locate the Location Points on the different utility lines. In this case, all the Location Points shown on the utility lines are also RFIDLIs.  
         [0087]      FIG. 6  shows a system  200  in accordance with one embodiment of the present invention. The system  200  includes an RFIDLI  160 , two Handheld Data Processing Units (HDPUs)  180  and  240 , and a Server  200 . A HDPU unit as mentioned earlier typically includes a Handheld RFID Reader and a handheld device (HD) such as a PocketPC or PDA. The Handheld RFID Reader reads from (and if read-write tag writes into) the RFID tag in an RFIDLI. The RFIDLI may be active or passive, depending on the range and other requirements.  
         [0088]     The HD is a PocketPC, PDA, smart wireless phone, or such, which runs the handheld software h-sw (as mentioned earlier). The RFID Reader of the HDPU communicates with the HD over a wireless connection like Bluetooth or a wired connection to send and receive data. The HD also communicates with the Server  200  (running the Server software) and other handheld devices running the h-sw or other software that is compliant with h-sw.  
         [0089]     The communication between a HD and the Server is done over wireless (GPRS or other) technologies or by synchronizing the HD with a PC (which could be the Server) from where data is loaded to the Server. The communication between two HDs is done over wireless. The communication protocol used between the h-sw and the Server software or other Handheld software is HTTP, TCPIP, UDP, SMTP, SOAP or other connection oriented or connectionless protocols. This is marked as  190  in  FIG. 6 . The data exchange can occur using a secure line using encryption and authentication or without such security.  
         [0090]     The HDPU may take any suitable form as will be appreciated by those of skill in the art. For example, the HDPU may have one or more Handheld RFID Readers (multiple readers to support different frequencies) and an HD, or may be a combined hybrid handheld device that includes RFID Reader (of one or more frequencies), microprocessor and memory to run our handheld software, wireless and/or wired communication capabilities, a screen to display data, the ability to input data and more. The HDPU may also have the ability to identify a location based on co-ordinates (GPS or relative, or both).  
         [0091]     As shown in  FIG. 6 , the HDPU  180  communicates with the RFIDLIs. The RFID Reader of the HDPU reads data from an RFIDLI and sends it to the h-sw (handheld software) running on the HD. The h-sw logs the data in local storage, if storage is available. The HD then sends data to the Server or to one or more other handheld devices running suitable software. If there is no wireless connectivity for the HD to send data to the Server immediately, or if the system is arranged for offline synchronization, the data is stored locally in the HD and later uploaded to the Server or another PC (from where it is moved to the Server). The decision to send the data to the Server or other Handheld may be configurable.  
         [0092]     Additionally, the h-sw can perform at least some of the following:  
         [0093]     It has a graphical interface to allow the user to enter data and also view data and reports on the screen.  
         [0094]     It communicates with the Server software and/or the handheld software in other HDPU devices to obtain other Location Data and other related data.  
         [0095]     It respects the security protocols of different levels for RFIDL 1   s  (important in defense applications and private applications, where not all information about mission critical utilities and objects should be available to everyone).  
         [0096]     It can print the reports using a printer or download the data to a PC.  
         [0097]     It has instant messaging and email capabilities to allow the user of the HDPU to communicate and collaborate with others instantly.  
         [0098]     It also communicates with the RFID Reader to provide it with the data that needs to be written into the non-volatile memory of an RFID tag in An RFIDLI. The write data is obtained from one of the following sources: 
        The Server software     An input file     Or via a GUI Interface that allows the user to input the data manually.        
 
         [0102]     The Server software (s-sw) runs on the Server hardware  200  of  FIG. 6 . The Server  200  receives the data (RFIDLI Content) read from the RFIDLIs by one or more HDPU units over a secure or non-secure channel as mentioned above. On receiving the RFIDLI Content, the s-sw&#39;s Data Management layer stores the data in the database (Server Database). In addition to this, the Data Management layer can read data from diverse data sources including files, databases and applications in real-time or batch mode. All received data is stored in the database (Database) or subsets of it can be channeled to other applications for further processing.  
         [0103]     The data from the Database is then processed using business rules to generate reports and provide business intelligence via the Web and wireless devices ( 210 ). The Server also sends out email notifications ( 220 ) based on business rules. The Server software also includes technology to allow business or non-technical users to specify the presentation of the information so the data is presented via the Web and wireless using the presentation layout specified. This increases the effectiveness of the information.  
         [0104]     As shown at asset  30 , data from the Server can be channeled to other external applications that are used to plot maps, ensure compliance with different regulations, inventory management, financial applications and more. The Server communicates with these applications using Web services, the APIs of the applications or specific tools and methods defined by the applications to allow the importing of data into the applications.  
         [0105]     The RFIDLI Content stored on the Server  200  in the database can be used to generate maps and other drawings showing the locations of the Hidden Objects in an area. In addition the data can be directly channeled to other applications to generate reports needed for compliance and other related processes.  
         [0106]     When implemented for a User Company (see definition above), the Server Database over time will include the Location Data Set for all their Hidden Objects that are associated with the RFIDLIs such that they can be used to locate a Hidden Object easily anytime. This data is referred to as the Company Location Database. When the solution is implemented for a User Company, the entire solution may be offered as a complete solution that includes maintaining, hosting and operating the Server and all other components of the invention.  
         [0107]     This invention also teaches the creation, compilation and maintenance of a master database of the Location Data Sets of the Hidden Objects along with the Location Data of the RFIDLIs belonging to some or all the User Companies that use this invention. This database is referred to as the Master Location Database and can be maintained as an ongoing service. This database will be highly secure and different views or snapshots of this information will be made available via the Web dashboards, wireless dashboards, files, database views or printed reports. The data may also be made available to other applications via Web services or other programming interfaces for a fee.  
         [0108]     The RFIDLIs, whether they are placed on the Hidden Object or in the vicinity, can be smart labels effectively used for repair and maintenance purposes. For example, when the maintenance staff goes to the field to perform maintenance work, they can be equipped with an RFID enabled badge to uniquely identify the staff. Next, when they perform repair or maintenance on the Hidden Object, information on the make, model, maintenance and repair history and more can be obtained via the HD in real-time using one or more RFIDLIs as reference points.  
         [0109]     Also, the maintenance or repair records for the work done at a particular location or section of the Hidden Object can be easily recorded (using the RFIDLIs as reference points) and sent to the Server Database for storage. The RFIDLI on or near the repair/maintenance location is read along with the RFID enabled badge of the staff. This allows easy retrieval of the records for that section of the Hidden Object and makes it easy to enter the current record via the HD. All the staff has to do is enter the description of the actual work performed; other data entry is minimized by reading the RFIDLI and the RFID enabled badge of the staff.  
         [0110]     The RFIDLIs, if they are on the asset or near it, can also be used to actively monitor the asset in real-time at different Location Points to determine its health and send out alerts if anything in case of an abnormality.  
         [0111]     Certain embodiments of the present invention will utilize common security techniques applied to certain aspect of the present invention that will be readily understood by those skilled in the art. According to these embodiments, the data stored in the non-volatile memory of the RFIDLIs (if using read-write tags) may be encrypted to provide security such that only those with authorization and the appropriate HDPUs can use the invention to detect the location of the Hidden Objects. Without the proper access privileges, if an RFID tag of any RFIDLI (Root Node RFIDLI, Intermediate Node RFIDLI, Starting RFIDLI or any other RFIDLI) is read using an RFID Reader, the contents of the RFID tag will be undecipherable.  
         [0112]     In other secure embodiments, even if a user has the authorization to read one or more RFIDLIs, the user will be able to locate and obtain information on only those Hidden Objects for which the user has access privileges. Access privileges will also determine which user can write what information into the RFIDLIs. The entire security management including encryption, key management, authentication and access control is a part of the solution.  
         [0113]     In addition to the above mentioned examples, various other modifications and alterations of the invention may be made without departing from the invention. Accordingly, the above disclosure is not to be considered as limiting and the appended claims are to be interpreted as encompassing the true spirit and the entire scope of the invention.