Error Size

~5 Feet (Horizontal)

Equipment

Trimble S5 Total Station

Result

Construction Rework

The Scenario

During a municipal infrastructure project for the City of Sebastian, Florida, a project report identified a significant discrepancy in the layout survey. The surveying team was using a high-end Trimble S5 total station to set control points for construction.

The Technical Error

Mechanism of Failure:

Incorrect Instrument Settings

Wrong Coordinate System = 5ft Shift

The instrument was initialized with the wrong coordinate system settings. While the total station measured angles and distances precisely, the internal translation to grid coordinates introduced a systematic horizontal shift of approximately 5 feet relative to the intended project design (State Plane).

Because construction layout relies entirely on these coordinates matching the CAD plans, every stake driven into the ground was 5 feet off-target.

The Consequence

The error forced a cascade of corrective actions:

  • Re-Survey Required: The errors had to be identified, isolated, and the site re-surveyed to establish correct control.
  • Quantity Adjustments: Construction quantities and layout plans had to be checked against the new, correct data.
  • Project Delay: Time was lost investigating why the "as-built" reality didn't match the design intent.

Professional Lesson

Precision is Not Accuracy.

Professional Lesson

Check Into Control. Every Time.

A 1-second total station can measure a wrong position very precisely. The only defense against this "instrument setting" error is a rigorous Check Into Control procedure. Before setting a single construction stake, shoot a known monument. If you miss by 5 feet, stop. Never assume the "black box" is right.

Source: City of Sebastian Public Records / Project Report

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