NCEES PS·Section 2 · Professional Survey Practices

GPS / GNSS Practice

Satellite constellations, static GPS, RTK, PPP, virtual networks — picking and operating the right one for the job.

The hook

Field GNSS is more than pushing buttons. Site selection, antenna setup, observation duration, mission planning, post-processing options — all decisions a surveyor makes that affect final accuracy. The PS exam tests workflow, not just technology.

  1. 1
    Mission planning
    Check satellite availability + PDOP for the planned observation window. Avoid times of poor geometry. Know the obstructions at the site.
  2. 2
    Equipment setup
    Tribrach + tripod plumbed over the point; antenna height measured precisely (slant or vertical, recorded with method); antenna model selected in the data collector.
  3. 3
    Observation
    Static: minimum 1-2 hours per session for short baselines; longer for higher accuracy or longer baselines. RTK: wait for fixed solution and stable accuracy estimates before recording.
  4. 4
    Quality control
    Check shots on a known point at start, mid, and end of the day. RTK base resets, antenna height re-checks, observed-vs-published comparison.
  5. 5
    Post-processing (static)
    Process baselines independently, then constrain to known control. Inspect baseline ratios, RMS, integer ambiguity flags. Re-observe if anything fails.
  6. 6
    Network adjustment
    Run least-squares with multiple baselines; inspect σ₀, residuals, error ellipses. Final coordinates only after a clean adjustment.
Memorize these

Concepts that show up on the exam

Static GPS
Long observations (hours) for highest accuracy. Used for control work.
RTK
Real-time kinematic. Cm-level accuracy in seconds, with active corrections from a base or network. Used for topo + boundary + layout.
Network RTK / VRS
Corrections from a state-operated network instead of your own base. Convenient; accuracy similar to single-base RTK.
OPUS
NGS's online static processing. Upload 2+ hours; receive published NAD83 coordinates. Free and authoritative.
PPP (Precise Point Positioning)
Standalone receiver + precise satellite orbits/clocks → cm-level accuracy without a base. Slower convergence.
Test yourself

How well did it stick?

A quick 5-question check on GPS / GNSS Practice. See where you stand and what to review.

More in Section 2
A. Public and Private Record Sources
Where to find records — public registry indexes, local survey office records, private + agency sources.
B. Documentation, Supervision, and Field Procedures
Field surveying techniques + practices. Data collection protocols. How to communicate them clearly to the crew.
D. Surveying Principles and Computations
Technical computations + the software ecosystem (TBC, Carlson, Civil 3D, OPUS, etc.).
E. Monumentation Standards
Applicable monumentation criteria + monument types. When and how to set them.
F. Land Development Solutions
Regulatory land development criteria, construction criteria, implementation procedures.
G. Survey Maps, Plats, and Reports
Technical communication via schematic, platting, and mapping. Picking the right deliverable for the audience.
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