RTK vs PPP: instant centimeters vs patient decimeters

Every precision GNSS product is built on one of two correction approaches. They differ in accuracy and cost, and — most importantly, and least advertised — in how long they take to get accurate.

RTK: instant centimeters, needs a data link

Real-Time Kinematic compares your receiver’s raw measurements against a reference — a local base station, or a modern continental correction network like the one behind Northing RTK. The defining property is no meaningful convergence time: a capable receiver reaches a fixed, ±2.5 cm-class solution in seconds and re-fixes in seconds after losing sky view. The price is a correction stream — you need connectivity (a phone’s data connection at ~1 kbps is plenty) and usually a subscription.

In our dual-receiver drive testing: fixed within seconds of cold start, fixed 88% of a 40-minute drive through tree cover and buildings, 1–2 s recovery after each obstruction.

PPP: cheap or free, but it makes you wait

Precise Point Positioning corrects satellite clocks, orbits, and atmosphere from a wide-area model. It needs no base station and can even work with no internet at all — but the receiver must converge: it sits refining its estimate for minutes to tens of minutes before the accuracy arrives, and losing sky view can restart part of that clock. PPP is excellent when the antenna holds still and patience is available; it is the wrong physics for continuous moving work.

Northing Global: the free mode built into every receiver

Northing Global is our name for the receiver’s built-in, no-subscription mode. It uses free high-accuracy correction broadcasts transmitted by the navigation satellites themselves — which is why it works anywhere on Earth with no account, no data plan, and no coverage zones. It is PPP physics, with PPP’s trade-offs, and we publish what we measured rather than what a brochure would like:

• Parked: after convergence, 50% of positions within 7.7 cm and 95% within 22 cm — genuinely useful for marking points, checking boundaries, finding a stake.
• Driving: 24–82 cm median depending on the segment, with convergence resets under obstructions. Treat any moving-vehicle precision claim for a convergence-based mode with suspicion, including ours.

The one-table version

	RTK (Northing RTK)	PPP	Northing Global
Accuracy class	±2–3 cm	3–20 cm	~10–20 cm converged
Time to accuracy	seconds	minutes to tens of minutes	minutes to tens of minutes
After signal loss	re-fix in seconds	partial re-convergence	partial re-convergence
Needs internet	yes (~1 kbps)	varies	no
Coverage	zones	varies	everywhere
Cost	subscription (year one included)	varies	free, forever

The practical summary: moving work wants RTK; static work tolerates convergence; Northing Global is the remarkable free fallback. That’s the logic behind shipping the receiver with a year of RTK included while keeping Global built in underneath — the physics picks the mode, not the marketing.