Winter RTK and Safety at a McKenzie County Well Pad
A two-person crew is performing a topographic survey for a well-pad access road in McKenzie County in January. The temperature is -18°F with a 25-mph wind. The crew plans to set an RTK base on a section corner and use a network roving solution because the base radio has been unreliable. The site is adjacent to a 115-kV transmission line, a produced-water pipeline marked by a yellow marker, and an active well pad with a warning sign for H2S. A subcontractor's 19-year-old rod person has no H2S training and no winter boots. The RTK solution drops from fixed to float near a metal shop building, with horizontal precision degrading from 0.04 ft to 0.35 ft and vertical from 0.06 ft to 0.55 ft. The crew leader wants to "shoot it anyway and average it out" to finish before dark.
1. Identify the safety issues and state what you would do before any more surveying takes place.
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This is a stop-work situation. The immediate hazards are H2S exposure, extreme cold, vehicle traffic, and high-voltage electrical clearance.
The rod person lacks H2S training and PPE. H2S is an immediate danger to life and health at sufficient concentrations, and the well pad is an active site. No one should enter the pad area without site-specific orientation, H2S training, a monitor where required, and the operator's permission. The missing winter boots are also unacceptable at -18°F with wind; frostbite can occur in minutes. The crew needs insulated boots, face protection, layered clothing, warming breaks, and a communication plan.
Near the 115-kV line, the crew must maintain the OSHA minimum approach distance and keep the rod, tripod, and antenna away from the conductors. The produced-water line marker indicates a buried utility; the crew should use the operator's locate and respect the tolerance zone.
I would stop work, notify the supervisor and the site operator, conduct a tailgate safety meeting, correct the PPE and training deficiencies, and not resume until the hazards are controlled. Production pressure before dark does not override these controls.
2. Evaluate the RTK float solution near the metal building. What would you do instead of averaging the float shots?
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I would not accept the float solution for topographic or control work. A horizontal precision of 0.35 ft and vertical of 0.55 ft is far worse than the fixed solution and is not improved by averaging many correlated shots. Multipath and poor satellite geometry produce systematic errors, not random noise that averages to zero.
The metal building is a likely multipath source. I would move the rover away from the building, reinitialize the RTK, and reobserve the point from a different location. I would check against a total station tie from a fixed control point, or use the total station for the obscured area entirely. If network coverage is unreliable, I would set a local base on a known point with a clear sky view and use a radio link, or run static GNSS on a control point and adjust it later.
For acceptance, I would require a fixed solution with documented precision and redundant observations. If the area cannot be surveyed reliably by RTK, I would collect it by total station and note the method. I would not average float shots and label them as topographic data.
3. What field documentation should accompany the survey so the office and the client understand the limitations?
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The field notes should record the date, time, temperature, wind, crew names, equipment serial numbers, base station location, coordinate system, and the RTK initialization method. For each point, record the solution status, horizontal and vertical precision, and whether it was fixed or float.
The notes should describe the metal building and any multipath area, the alternate total station ties, the control points used, and the check shots. If any area was surveyed by total station, the instrument setup and backsight should be documented.
The final map should carry a note that RTK points in the vicinity of the metal building were supplemented or replaced by total station observations, and it should state the horizontal and vertical accuracy. The client should receive the control report and the survey metadata, not just a line drawing. This documentation protects the surveyor and tells the contractor which points are suitable for construction layout.