Pipeline following sensor arrangement
A method and apparatus for installing a monitoring cable or other utility near an existing pipeline. An electromagnetic signal may be induced on the pipeline, either directly, or by transmitting a signal from a vehicle carrying a sensor array. The sensors disposed on the vehicle communicate with a processor to determine a distance and orientation of the vehicle relative to the pipeline. The signal may be electromagnetic, acoustic, capacitive, or the like. A plow or other digging tool may be on the vehicle or a secondary vehicle. Such a digging tool opens a trench and installs the cable along a path disposed next to the pipeline within an acceptable distance range from the pipeline. The vehicle may be remotely or automatically operated.
1. A system comprising:
a mobile machine frame;
an outrigger frame attached to the mobile machine frame;
a first receiver, a second receiver, and a third receiver, each of the first, second and third receivers disposed linearly on the outrigger frame at a known distance from each of the other of the first, second and third receivers, in which the receivers are each configured to detect a signal emanating from an underground utility line;
an orientation sensor disposed on the outrigger frame and configured to transmit an orientation signal indicative of an angle of the outrigger frame relative to level plane; and
a processor configured to determine a position of the underground line using the signal received at each of the first, second and third receivers and the orientation signal.
2. The system of claim 1 in which the processor is configured to determine a path of travel for the mobile machine frame using the position of the underground utility line.
3. The system of claim 1 further comprising a memory, in which the processor is configured to store the position of the underground utility line in the memory.
4. The system of claim 3 further comprising:
a plow blade configured to open a trench proximate the position of the underground utility line; and
a length of cable.
5. The system of claim 4 in which the plow blade is disposed on the mobile machine frame.
6. The system of claim 1 in which the processor is configured to:
determine a detected source location of each of the signals;
compare the detected source locations by plotting a polygon; and
determine a predicted location and an estimated error in the predicted location of the underground utility line using an area of the polygon.
7. A method comprising:
placing an electromagnetic signal on an underground line;
translating a mobile frame comprising an attached outrigger frame on the ground such that the outrigger frame is overlying a length of the underground line;
while the mobile frame is translating on the ground, detecting the signal, simultaneously, at three locations on the outrigger frame, wherein the three locations are disposed along a line;
while the mobile frame is translating on the ground, detecting, with an orientation sensor, the angle of the line on which the three locations are disposed relative to a level plane as the mobile frame translates on the ground;
using each of the detected signals along with the detected level and location, determining an estimated position of the underground line;
from the estimated position, determining a predicted location of the underground line and an estimated error value in the predicted location.
8. The method of claim 7 further comprising:
causing the mobile frame to travel on a path upon which a strength of the electromagnetic signal does not fall below a predetermined level.
9. The method of claim 7 further comprising:
comparing the estimated error value to a predetermined threshold; and
stopping the translation of the mobile frame when the error value exceeds the predetermined threshold.
10. The method of claim 7 further comprising:
determining, from the predicted location of the underground line, a preferred path for a monitoring line; and
installing the monitoring line along the preferred path.
11. The method of claim 10 in which the step of installing the monitoring line comprises opening a trench with a plow blade.
12. The method of claim 11 wherein the plow blade is disposed on the mobile frame.
13. The method of claim 7 in which the underground line comprises a high pressure gas pipeline having a known diameter.
14. The method of claim 7 , in which the step of determining an estimated error value comprises:
plotting each of the estimated locations of the underground line; and
determining an area defined by a polygon having vertices at each of the estimated locations.
15. The method of claim 14 further comprising ceasing translation of the mobile frame if the area exceeds a predetermined threshold.