Method and apparatus for precisely locating a buried utility conveyance
First Claim
1. A method for precisely locating a utility conveyance buried a prescribed depth below the earth, comprising the steps of:
- impressing a conveyance-locating tone on the conveyance so that the conveyance radiates a first electromagnetic field within a first proximity zone that has a radius about the conveyance at least as great the depth of burial of the conveyance;
impressing on the conveyance a low frequency conveyance-confirmation tone that is pulsed in a particular pattern unique to the conveyance to be located so that the conveyance radiates a second electromagnetic field unique to the conveyance within a second proximity zone that has a radius about the conveyance less than the depth below which the conveyance is buried;
sensing, via a first signal detector located above the earth, where the first electromagnetic field has its greatest strength to establish a region where the conveyance is generally located;
inserting into the earth, within the region where the conveyance is generally located, a second signal detector to detect whether the second field is present, and if the second field is not present then;
inserting the second signal detector in the earth at successive positions within the region where the conveyance is generally located until the second field has been detected.
1 Assignment
0 Petitions
Accused Products
Abstract
An underground utility conveyance (10) may be precisely located by impressing both a locating tone and a confirmation tone on the conveyance. The locating tone is an RF signal that produces a first field that radiates above the earth that is sensed by a first, above-ground signal detector (22) to establish the general location of the conveyance. The confirmation tone is a near-DC signal that produces a second, field having a relatively limited radiation path. A second detector (24) is inserted into the earth at successive places in the region where the conveyance is located to establish its precise location.
171 Citations
8 Claims
-
1. A method for precisely locating a utility conveyance buried a prescribed depth below the earth, comprising the steps of:
-
impressing a conveyance-locating tone on the conveyance so that the conveyance radiates a first electromagnetic field within a first proximity zone that has a radius about the conveyance at least as great the depth of burial of the conveyance; impressing on the conveyance a low frequency conveyance-confirmation tone that is pulsed in a particular pattern unique to the conveyance to be located so that the conveyance radiates a second electromagnetic field unique to the conveyance within a second proximity zone that has a radius about the conveyance less than the depth below which the conveyance is buried; sensing, via a first signal detector located above the earth, where the first electromagnetic field has its greatest strength to establish a region where the conveyance is generally located; inserting into the earth, within the region where the conveyance is generally located, a second signal detector to detect whether the second field is present, and if the second field is not present then; inserting the second signal detector in the earth at successive positions within the region where the conveyance is generally located until the second field has been detected. - View Dependent Claims (2, 3, 4)
-
-
5. Apparatus for precisely locating a utility conveyance buried a prescribed depth below the earth comprising:
-
means for impressing a conveyance-locating tone on the conveyance so that the conveyance radiates a first electromagnetic field within a first proximity zone that has a radius about the conveyance at least as great the depth of burial of the conveyance, and for impressing a low frequency conveyance-confirmation tone that is pulsed in a particular pattern unique to the conveyance to be located so that the conveyance radiates a second electromagnetic field unique to the conveyance within a second proximity zone that has a radius about the conveyance less than the depth below which the conveyance is buried; a first signal detector located above the earth for sensing where the first field has its greatest strength to establish a region where the conveyance is generally located; and a second signal detector that is insertable within the earth to detect if the second field is present. - View Dependent Claims (6, 7, 8)
-
Specification