Antenna Setup Errors
A receiver can have excellent satellite geometry, a short baseline, and calm atmospheric conditions, and still produce an untrustworthy coordinate, because of something much closer to the ground: how the antenna itself was configured before the survey ever began.
Antenna setup errors do not announce themselves. A wrong antenna profile or a mismatched height entry produces a coordinate that still reaches FIX with complete confidence, offset by exactly the amount the setup error introduced.
The Antenna Model Selected in Software
Field software asks which antenna model is in use because different antennas have different, individually calibrated offsets between their physical reference point and their actual electrical phase center, published by manufacturers and standards bodies for exactly this purpose. Selecting the wrong model in software, an easy mistake when switching equipment or using a generic profile, applies the wrong calibration offset to every position the receiver computes, silently and consistently.
An incorrect antenna model selection behaves exactly like a small, constant vertical and sometimes horizontal bias. It will not trigger a warning, and it will repeat identically on every point collected under that same incorrect profile.
The Measurement Method, Not Just the Number
As the first companion in this series noted, most data collectors ask not just for an antenna height, but for how that height was measured: vertical to a reference point, slant to a marked notch, slant to a different manufacturer mark, or true vertical. Each option applies a different internal conversion before the number reaches the phase center calculation. Entering a perfectly accurate height measurement against the wrong measurement method still produces a wrong result, and the number itself gives no indication that anything is amiss.
A Habit Worth Building Into Every Setup
Confirming the antenna model and measurement method at the start of a session takes a few seconds and catches an entire category of error that no amount of satellite geometry, baseline management, or atmospheric luck can reveal on its own. A wrong setting here behaves exactly like a real, if small, positioning error, and it will pass every internal check the receiver is capable of running, because the receiver has no way to know its own configuration is wrong.
Every point collected during a session carries what looks like a small, consistent vertical offset compared to known control, while horizontal positions look fine. Before suspecting the geoid model or the reference frame, what setup detail is worth checking first? The antenna model and measurement method selected in the field software for that session.
An incorrect antenna model or a mismatched measurement method produces a consistent, silent offset in every point collected under that setup. Neither error is visible in the FIX status, and confirming both at the start of a session is one of the simplest, highest-value verification habits available to a field crew.
The antenna's software profile is only half the physical setup story. The other half is whether the pole holding it was actually plumb when the point was collected.