Tier Six: Longer Static Log Against Rapid or Final Products
Extend the same logging idea from the last chapter considerably longer, several hours rather than under an hour, and process it against increasingly refined satellite orbit and clock products, and the result climbs meaningfully closer to the accuracy ceiling this companion's final method represents.
A longer static log, several hours or more, processed against rapid or final precise orbit and clock products rather than broadcast information, produces an accuracy that approaches full commissioning without requiring a full month of observation.
Trading Calendar Time for a Better Result, Deliberately
Longer observation sessions average down random error more thoroughly, the same principle behind survey-in, but this time paired with genuinely superior satellite information rather than left to compensate for uncorrected systematic bias alone. Rapid orbit and clock products, available within roughly a day or two, already meaningfully outperform broadcast information, and waiting for final products, available within two to three weeks, sharpens the result further still.
This method's accuracy gain comes from two sources working together, more observation time reducing random error, and better satellite products reducing systematic error, rather than from either one alone.
Two Genuinely Different Free Services, Not Two Names for One
Where the rapid-static service from the last chapter is built for shorter sessions and speed, a standard static processing service is built to make full use of a considerably longer observation and the most refined satellite products available at the time. Two free, real, currently operating services represent the two genuinely different mechanisms behind this tier. NGS's standard OPUS service performs a double-differenced network adjustment, the same underlying mechanism as OPUS-RS, against United States reference stations, tied to the National Spatial Reference System. NRCan's CSRS-PPP, by contrast, is pure PPP: no differencing against any reference station at all, just direct modeling of error using precise global satellite products, which means it can process a raw log from anywhere on Earth with no dependence on nearby CORS density whatsoever.
Choosing between OPUS and CSRS-PPP is not a matter of picking whichever term is more familiar. OPUS performs a double-differenced adjustment against a network of nearby reference stations. CSRS-PPP performs pure PPP, modeling error directly with no reference stations involved at all. Both are free, both are real, and they solve the same problem through genuinely different mechanisms.
Where Each Tool Actually Reaches
OPUS's dependence on nearby United States reference stations makes it, in practice, mainly a United States tool. CSRS-PPP's independence from any reference station at all makes it genuinely usable almost anywhere on Earth, United States included, not merely a Canadian tool that happens to also accept foreign data. CSRS-PPP can return its position in ITRF, a globally standard, country-neutral reference frame, alongside its native NAD83(CSRS) output, and NAD83(CSRS) itself sits close enough to the United States' own NAD83(2011), generally within a meter and often much closer, that plenty of United States surveyors use CSRS-PPP directly, particularly when they want its additional GLONASS and Galileo support or simply want a second, independent service to check a position against, though a project mixing NAD83(2011) and NAD83(CSRS) coordinates for precise, absolute work should apply the actual published transformation between them rather than treat "close" as "identical."
CSRS-PPP being run by the Canadian government does not make it a Canada-only tool. Its freedom from nearby reference stations, combined with an ITRF output option and a NAD83(CSRS) realization that stays close to the United States' own NAD83(2011), makes it one of the more genuinely global free processing services available, not a foreign alternative with a narrow home territory.
Where This Sits in the Overall Range
A project willing to invest several hours of logging and wait one to three weeks for the most refined satellite products reaches an accuracy level most everyday work never actually requires, closing in on what the full month-long approach delivers without committing to that entire calendar span. It remains a real step below full commissioning, covered next, in both duration and the statistical strength that comes specifically from independent, multi-day sampling.
A project logs six hours of static data and processes it against final precise orbit products three weeks later. Is that meaningfully different from a single, shorter rapid-static session? Yes. The longer observation and the more refined products both reduce error the shorter session could not, even though neither one alone reaches the rigor of a full month-long commissioning effort.
A longer static log, processed against rapid or final precise products rather than broadcast information, combines more averaging time with meaningfully better satellite data, reaching an accuracy level that approaches full commissioning without its full calendar commitment. OPUS and CSRS-PPP are two free, genuinely different ways to do that processing: a double-differenced network adjustment whose practical reach is mainly the United States, or pure PPP usable on a raw log from almost anywhere on Earth, including the United States itself.
One method remains, the one this companion's opening chapter used to define the far end of the entire range in the first place.