Abstract:
To locate a buried conveyance ( 10 ), electromagnetic signaling information is collected at spaced intervals along the conveyance with the aid of a locating device ( 14 ). A processor ( 21 ) receives such information from the locating device ( 14 ) and then geographically orders the information in accordance with the geographic coordinates of the location at which it was obtained. Once geographically ordered, the information is then provided on a display ( 22 ) to provide a visual representation of the information as a function of the conveyance length.

Description:
TECHNICAL FIELD 
     This invention relates to a technique for providing information gained from locating an underground conveyance by electromagnetic signaling. 
     BACKGROUND ART 
     Many utilities, such as AT&amp;T, bury their pipes and cables (“utility conveyances”) underground both for reasons of safety and esthetics. Underground burial often provides protection to such utility conveyances against weather and other sources of potential damage. Utilities that undertake burial of their conveyances usually make extensive efforts to plot the location of each buried conveyance on a map to facilitate its location in case of repair or replacement. While a map will indicate the general location of a buried conveyance, more precise location information often becomes necessary, particularly in urban environments. For that reason, most utilities that bury their conveyances underground typically rely on electromagnetic signaling techniques to precisely locate such conveyances. 
     U.S. Pat. No. 5,644,237, issued in the names of Hossein Eslambolchi and John Huffman, on Jul. 1, 1997, and assigned to AT&amp;T, (incorporated by reference herein) discloses an electromagnetic signaling technique for locating a buried utility conveyance. A signal generator applies a locating signal and a confirmation signal to a metallic part of the conveyance. In the case of an optical fiber cable, the metallic part comprises either a metallic sheath or a copper trace wire within the cable. Using a signal detector, a technician detects both the locating signal and the confirmation signal radiated above ground to precisely locate the buried conveyance. 
     Often, a technician will locate separate portions of the conveyance at different locations along its length. Many of the signal detectors available for detecting conveyance locating signals have the capability of storing certain data collected during a locate operation. Such stored information data allows the technician to gain certain insights about the stored conveyance. Moreover, storing such information may prove useful for later analysis. 
     Traditionally, the stored conveyance location data, while useful, did not provide an overall representation of the conveyance. Moreover, the location data for each discrete portion of the conveyance provided no ability to facilitate readily combination with the location data associated with other discrete conveyance portions. 
     Thus, there is a need for a technique that provides location data representative of the entire conveyance. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly, in accordance with a preferred embodiment, the present invention provides location information for a buried conveyance. Initially, location data associated with each of a plurality of discrete conveyance portions is obtained, usually by a technician, who undertakes a locate operation at various spots along the conveyance. The location data for each discrete conveyance portion includes geographic coordinate information, typically obtained by a GPS unit, as to where the location information was obtained. Thereafter, the physical proximity of each discrete conveyance portion is established relative to the other discrete conveyance portions for which location information was obtained. Thereafter, the location data for the discrete conveyance portions is arranged in geographic sequence corresponding to the proximity of the discrete conveyance portions to each other. In this way, the location information associated with each discrete conveyance portion is arranged with the next closest discrete conveyance portion to provide a piece-wise set of location data for display. If desired, the piece-wise locating data can be smoothed using well-known curve filling techniques to yield a continuous function representative of the location data as a function of the conveyance length. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a schematic diagram illustrating the manner in which location data is obtained for discrete portions of a conveyance buried underground; 
     FIG. 2 shows a graphical representation of a data record obtained during a locate operation performed on a discrete portion of the conveyance of FIG. 1; and 
     FIG. 3 shows a chart of locating data displayed in accordance with the teachings of the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts a utility conveyance  10 , such as an optical fiber cable, buried below the surface of the earth  12 . During burial of the conveyance  10 , the entity (e.g., service provider) responsible for its maintenance will typically plot the location of the conveyance  10  on a map. However, such location information usually lacks the precision needed in the event of repair or replacement of the conveyance  10 . For that reason, when conveyance repair or replacement becomes necessary, the service provider will typically dispatch a technician (not shown) to precisely locate the conveyance  10  via electromagnetic signaling. 
     To locate a conveyance using electromagnetic signaling, the technician will employ a locating device,  14 , such as a PDL  4  locating device manufactured by Radiodetection, Inc, Mahwah, N.J., to detect at least a locating signal impressed on a metallic part of the conveyance. The metallic part of the conveyance may include the conductive sheath portion of a fiber optic cable or the entire conveyance itself in the case of a metal pipe. To achieve more precise location in accordance with the teachings of U.S. Pat. No. 5,644,237 (incorporated by reference herein), the metallic part of the conveyance  10  will carry both a locating signal as well as a confirmation signal. By using the detector  14  to detect both the locating and confirmation signals, a technician can locate the conveyance  10  with greater precision than by detecting the locate signal alone. 
     In practice, a technician seeking to locate a conveyance, such as the conveyance  10 , will detect the locate signal at several different spots along the conveyance. Typically, locating device  14  has the capability of storing the locate information obtained at each spot along the conveyance  10 . Heretofore, the stored locating data, while useful, could not readily be displayed to provide an overall representation of various locating attributes for the conveyance as a function of its length. 
     The present invention discloses a technique for providing an overall representation of various locating attributes for the conveyance as a function of its length. To that end, the locating device  14  includes a Global Position Satellite location unit  15  that determines the exact location of the locating device  14  using GPS measurements (within the error limits associated with such measurements). Each time a technician performs a location measurement on the conveyance  10 , the GPS locating unit  15  determines the geographic coordinates of the locating device  14  for storage along with other locating information determined by the locating device. 
     FIG. 2 shows a data record  20  stored by the locating device  14  for a discrete locate operation performed by the technician at a particular spot along the conveyance  10  of FIG.  1 . The data record  20  for each discrete locate operation performed by the technician includes a plurality of data elements  20   1 - 20   n (where n is a integer) each indicative of a particular attribute associated with the locate operation. Among the attributes included within the data record  20  is the GPS coordinates, represented by attribute  20   1 , the conveyance depth, represented by attribute  20   2 , the strength of the locate signal, represented by attribute  20   3  and the electrical current carried by the conveyance  10 , represented by attribute  20   4 . Others of the attributes  20   5 - 20   n , may include the time and date of the locate operation, the owner of the conveyance, as well as information associated with the locating device  14 . 
     The locating device  14  of FIG. 1 will download each data record  30  of FIG. 2 to a data processor  21  shown in FIG. 1 that typically takes the form of a personal computer having an associated display  22  that may be integral with the computer, as in the case of a portable lap top, or separate in the case of a desk top. The processor  21  combines the data records  30  in geographic sequence to yield an overall representation of the location of conveyance for display on the display  22 . For example, the processor  21  of FIG. 1 may combine the data records in geographic sequence to provide a graph of the conveyance depth as a function of length, as represented by the chart  24   a  of FIG. 3, while simultaneously providing chart  24   b  that depicts the locating signal strength as a function of conveyance length, and chart  24   c  depicting the conveyance current as a function of length. The charts  24   a - 24   c  of FIG. 3 are merely exemplary and others of the attributes  20   1 - 20   n  of FIG. 2 that typically vary as a function of length could also be displayed in place or, or in addition to the charts  24   a - 24   c.    
     In processing the information contained in the data records  30  to provide the display(s) on the display  22  of FIG. 1, the processor  21  of FIG. 1 will first determine the geographic proximity of conveyance portion corresponding to the particular data record to enable the processor to order (i.e., arrange) the data records in geographic sequence. In other words, the processor  21  will geographically sequence the data records  30  such that the data record obtained during a locate operation associated with a particular discrete conveyance portion will follow the data record associate with the next proximate conveyance portion. 
     Depending on the physical distance between discrete conveyance portions on which locate operations have been performed, the displayed data may appear somewhat disjointed. The processor  21  could smooth such piece-wise data using well-known curve-fitting techniques to provide a less disjointed display, thereby providing overall representation of the particular location attribute as a function of conveyance distance. 
     The foregoing discloses a technique for providing locating information associated with a buried conveyance, and more particularly, for providing locating information as a function of the conveyance length. 
     The above-described embodiments merely illustrate the principles of the invention. Those skilled in the art may make various modifications and changes that will embody the principles of the invention and fall within the spirit and scope thereof.