Free public NTRIP casters

You don't need a paid subscription to get RTK corrections. These public NTRIP casters stream GNSS corrections for free — some to anyone, some after a free registration. The station counts below come straight from each caster's live source table.

Text last reviewed 2026-10-07. Station counts update automatically.

At a glance

Caster	Mountpoints	Address	Access
Centipede-RTK	1293	crtk.net:2101	Free, no sign-up. Open collaborative network, densest in France.
RTK2Go	781	rtk2go.com:2101	Free, no sign-up. Community base stations; quality varies per base.
IGS NTRIP Data Center	385	www.igs-ip.net:2101	Free after registration. Global IGS reference stations and real-time products.
EUREF-IP	222	www.euref-ip.net:2101	Free after registration. EUREF Permanent Network reference stations across Europe.
SAPOS (15 German networks)	85	one caster per state	Official German state service. Free in most states under open-data rules; registration required.
Kadaster NL	61	ntrip.kadaster.nl:2101	Dutch national reference stations operated by Kadaster.

RTK2Go — open community caster

RTK2Go is a free community caster run by SubCarrier Systems, the makers of the SNIP caster. Anyone can publish a base station to it and anyone can connect as a rover, so it has bases in places no official network covers. The flip side: stations are run by volunteers, so check that a base is online, close to you and broadcasting the constellations your receiver needs.

Caster rtk2go.com, port 2101.
No sign-up for rovers, but you must use a valid email address as the user name. If your client can't type @ or ., write -at- and -d- instead. Use the password none if one is required.
Rules and status: rtk2go.com.

Centipede-RTK — open collaborative network

Centipede-RTK is an open network of shared base stations, started in France for precision agriculture and now spreading to other countries. It is free and needs no account.

Caster crtk.net, port 2101, NTRIP v1 or v2, RTCM 3.
No login needed; if your client insists, use centipede / centipede.
Mountpoint NEAR connects you to the closest working base automatically (NEAR4 for a lighter MSM4 stream).
One device per IP address. Docs: docs.centipede.fr.

EUREF-IP and IGS-IP — reference-grade, free registration

EUREF-IP streams the EUREF Permanent GNSS Network across Europe, and the IGS NTRIP casters stream International GNSS Service stations worldwide. These are geodetic reference stations, so they are spaced far apart: excellent for PPP and research, but often too distant for quick RTK fixes.

Free, but you need an account: register once at register.rtcm-ntrip.org.
Port 2101 (TLS on 443 is also offered).

SAPOS — official German state networks

Each German state runs its own SAPOS service. Most states now provide the centimetre-level HEPS service free of charge under their open-data rules, but you still have to register with the state's SAPOS office, and terms differ per state. Start at the SAPOS central office. SAPOS mountpoints are usually network (VRS-style) streams, so the list per state is short even though coverage is complete.

How to choose

Distance first. RTK accuracy drops by roughly 1 mm per km from the base, and fixes get slower and less reliable past 20–30 km. Use the map to find the closest base.
Check the stream. Your receiver needs the base position message (RTCM 1005 or 1006) and observations for the satellite systems it tracks (MSM4 or MSM7 messages). The station popup on the map shows each base's format and satellite systems; the caster's source table lists the exact message types.
Prefer official networks for paid work. Community bases can move, go offline or have a wrong reference position. For surveys you will sign off on, use a state or national network where one exists.

Ready to set up? Follow how to connect an RTK rover to an NTRIP caster.