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Short answer
We choose a GNSS method around when coordinates are needed, how reference information reaches the workflow and how the result will be checked. RTK supports positioning during observation; PPK processes recorded rover and reference observations afterward; PPP uses precise satellite products and suitable observations. None removes the need to document references and independently check the result.
- A correction link, raw observation record and validation plan are different requirements.
- PPP may operate in real time or in post-processing; it still depends on upstream reference infrastructure and products.
- Ambiguity status and reported precision are diagnostics, not a substitute for independent accuracy checks.
Who this is for: Survey managers, GNSS field teams and engineers specifying a coordinate deliverable.
Compare the workflow before the accuracy claim
RTK and network RTK use reference information while the rover is operating. A functioning communications link is part of that workflow. PPK moves the relative-positioning calculation into the office using recorded observations with suitable time overlap. It does not reconstruct information that was never observed.
PPP is a different processing approach rather than simply a synonym for offline surveying. Precise orbit, clock and, where applicable, bias products support the solution. A service's supported observations, products and reference context must be checked for the survey date.
| Your requirement | Method to evaluate | Evidence to check |
|---|---|---|
| Coordinates needed while observing | RTK or network RTK | Correction delivery, reference setup, interruptions and independent control |
| Results can wait; field connectivity is unreliable | PPK | Raw observations, reference access, time overlap and antenna metadata |
| Suitable observations and processing products are available | PPP | Service support, convergence behaviour, diagnostics and output reference context |
Technical references: NOAA NGS: real-time GNSS user guidelines (2008); NRCan: CSRS-PPP information and updates; IGS: precise GNSS products.
Define acceptance before choosing equipment
We start with the decision the coordinates will support. A mapping inventory, control network and setting-out task do not automatically share the same tolerances. Specify horizontal and vertical checks separately, identify the coordinate reference and decide which points or observations can provide an independent comparison.
Then test the actual setup on a representative part of the site. Open ground alone will not establish performance beside walls, under vegetation or through a communications interruption. Record a failed or interrupted observation instead of silently treating the last accepted position as current.
- Confirm the deliverable, reference system, units and acceptance tests.
- Check reference-data or correction-service access before mobilising.
- Record receiver, antenna type, antenna reference point and measured antenna height.
- Preserve observation times and raw data where the workflow supports them.
- Keep processing settings, product identifiers and the software version with the result.
Technical references: NOAA NGS: real-time GNSS user guidelines (2008); NRCan: CSRS-PPP information and updates.
Read diagnostics alongside an independent check
A fixed ambiguity solution tells you something about the processing state. It does not demonstrate agreement with the control used by the receiving project. A precise-looking coordinate can still carry an incorrect base coordinate, antenna-height error or unsuitable reference transformation.
PPP ambiguity resolution also depends on compatible products and processing conventions. Product-quality tables from a GNSS service describe those products; they are not a universal promise about an individual rover result. We would report residuals, repeatability, independent comparisons and unresolved gaps as distinct evidence.
Technical references: IGS: PPP ambiguity-resolution working group; IGS: precise GNSS products; NOAA NGS: real-time GNSS user guidelines (2008).
Use the pilot to expose the real constraint
If results are needed immediately, solving the reference and communications problem may be more important than changing the processing label. If control access or reference consistency is unclear, resolve that before presenting a method as the answer.
What should accompany the coordinate file?
Our recommendation is to keep this record readable by another survey team. A spreadsheet of coordinates without its method and reference context is difficult to audit or reuse.
- Observation dates and intervals, receiver and antenna metadata, and reference inputs.
- Source and output reference frame, relevant epoch and height information.
- Processing configuration, exclusions, ambiguity and quality diagnostics.
- Independent check results with the comparison method and acceptance criteria.
- Known interruptions, weak areas and any further observations needed.
Technical references: NOAA NGS: real-time GNSS user guidelines (2008); NRCan: CSRS-PPP information and updates.
Common questions
Is PPP always an offline method?
No. PPP can be implemented in real time or with post-processing. Check the particular service, available products, supported observations and output reference context.
Does PPK guarantee a better result than RTK?
No. PPK changes the workflow and allows office processing of recorded observations. Observation quality, reference inputs, antenna records, configuration and independent validation still determine what can be supported.
How long must I observe for a centimetre result?
There is no universal session length in this guide. The method, receiver, environment, geometry, products, required confidence and acceptance test must be evaluated for the actual survey.
Official references
Sources checked 1 November 2026. The linked publishers remain the authority for their specifications and services.
- NOAA NGS: real-time GNSS user guidelines (2008)
Historical field-method guidance, used for observation and checking principles, not as an Indian project standard.
- NRCan: CSRS-PPP information and updates
Service-specific processing, precise products, antenna handling and output reference context; includes a 2026 update.
- IGS: precise GNSS products
Upstream orbit, clock and reference products; product performance must not be confused with rover accuracy.
- IGS: PPP ambiguity-resolution working group
Compatibility and conventions for PPP ambiguity-resolution products.