Glossary

Core RTK and NTRIP terms, in plain language. For orientation only, not a precise technical definition.

GNSS

An umbrella term for satellite positioning systems (GPS, Galileo, GLONASS, BeiDou…).

RTK

Real-Time Kinematic — a surveying method that reaches centimetre accuracy in real time thanks to corrections from a reference station.

Reference (base) station

A fixed receiver on a known point that broadcasts corrections your receiver uses to refine its position.

NTRIP

The protocol that carries corrections over the internet — a receiver connects to a server and subscribes to a stream.

Caster

The server that distributes correction streams. It has an address (host and port), e.g. caster.example.com:2101.

Mountpoint

One specific correction stream on a caster. A caster usually offers several — each typically belongs to a different station or network.

Sourcetable

A caster's list of mountpoints with their properties (position, constellations, format) — its “menu”.

RTCM 3

The standard format of correction messages. Fixcast decodes these and builds a verdict about the stream's state.

MSM vs. legacy

Two “dialects” of RTCM messages. MSM (1071–1127) is newer and more universal; “legacy” (1004/1012) is the old format. An MSM-only stream may not work on a very old receiver.

VRS / network mount

Virtual Reference Station — the network computes corrections for your exact location, so the receiver must send its position (a GGA message).

GGA

The message a receiver uses to report its position. Network (VRS) mounts require it; without it the stream stays silent.

SSR vs. OSR

Two approaches to corrections. OSR sends ready-made corrections for an area (ordinary RTK); SSR (state-space) sends error models separately and not every receiver handles them.

Fix / float

The position-solution state. “Fix” = ambiguities resolved, centimetre accuracy; “float” = only decimetre-level so far.

PDOP / DOP

A measure of how well satellites are spread across the sky. The lower the number, the better the geometry and the more precise the position.

Correction age

How old the last received correction data is. A growing age means a delayed or interrupted stream.

Ionosphere / ROTI

Ionospheric activity affects the signal. ROTI indicates its turbulence — higher values make reaching a fix harder.

H3

A system of hexagonal cells covering the Earth. Fixcast aggregates data in it so precise locations are never published.

K-anonymity

The rule that a cell is shown only above a certain number of measurements — so an individual can't be singled out.