DATA CHECKED OCT 2026
Illinois / State-run network

ICORN (coming 2027)

Restricted  Illinois DOTDepartment of Transportation. The state agency that runs many of the free state RTK networks.More

Plans & pricing

Price not published
Free once public
Constellations
GPSThe US satellite navigation system. People often use "GPS" to mean all satellite positioning.More, GLONASS, Galileo, BeiDou, QZSS
Correction formats
RTCMThe common format RTK corrections are written in, so different brands can understand each other.More.x via NTRIPThe standard way RTK corrections are sent over the internet. Think of it as internet radio for correction data.More
Datum / Reference frameA precise version of a datum, defined by real stations on the ground. ITRF2020 and NAD 83(2011) are examples.More
Aligned with ITRFInternational Terrestrial Reference Frame. A worldwide datum. In the US it's about a meter different from NAD 83.More and NGSNational Geodetic Survey. The part of NOAA that runs the official US coordinate system, CORS and OPUS.More standards
Network
Station spacing 35-50 km, statewide deployment in progress

NTRIP caster

hostProvided after signup
PortA number that tells your device which "door" on the caster server to use. For NTRIP it's often 2101.More—
In internal testing, with public launch planned for early 2027. Not usable yet.
Checked 2026-10-16 Sources: [1] · Blank fields mean the operator doesn't publish it · Report a change

Reliability reports

Collecting soon

No user reports yet for ICORN (coming 2027). We only show real reports from real users, never sample data. Report collection opens soon, and here's what we'll ask:

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Price changes. New stations.
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