Introduction to RTK Networks (CORS): How a Network of Base Stations Works

Introduction

Setting up your own RTK base station works, but it's extra equipment, setup time, and limited range. RTK networks solve this by providing corrections from permanent stations covering entire regions.

What Is a CORS Network?

CORS stands for Continuously Operating Reference Station. It's a network of permanent GNSS base stations that run 24/7/365, have precisely known coordinates, log data continuously, and provide corrections to users on demand.

Types of CORS Networks

• National/Governmental: NOAA CORS (US, ~2,000 stations), EUREF (Europe, ~300 stations), Geoscience Australia (~500 stations), typically free access
• Commercial: Trimble VRS Now, Leica SmartNet, John Deere RTK, subscription required
• Regional/Local: State/provincial networks, utility company networks, often free within jurisdiction

What CORS Provides

• Real-time services: RTCM corrections via NTRIP for RTK users (single-base or VRS)
• Post-processing: Raw RINEX data download for static and PPK users, often free
• Products: Precise coordinates, atmospheric data, plate motion monitoring

Network RTK Methods

• Single-base: Use nearest physical station. Simple and works, but accuracy degrades with distance.
• VRS (Virtual Reference Station): Network creates a virtual base station at your location for best accuracy. Requires two-way communication.
• FKP (Fl??chenkorrekturparameter): Broadcasts area correction parameters. Less common.
• MAC (Master-Auxiliary Concept): Master station plus auxiliaries with compact corrections.

Network Accuracy

A well-designed network maintains 2–3 cm throughout its coverage area.

Connecting to a CORS Network

You need an RTK-capable rover, a cellular data connection, and an NTRIP client (usually built-in). The process: find the nearest CORS network, sign up for access if required, configure your rover with the NTRIP server address (port 2101 typically), select a mountpoint, and connect.

Building Your Own Network

For large projects or organisations: stations spaced 30–70 km apart with surveyed coordinates, reliable power and internet, central processing software, and a data distribution system. Cost per station: $10,000–$20,000 equipment, $5,000–$10,000 installation, $2,000–$5,000/year maintenance.

CORS for Other Applications

• Meteorology: Tropospheric delay → precipitable water vapour → improved weather prediction
• Space weather: Ionospheric monitoring and total electron content maps
• Geophysics: Plate tectonics, earthquake deformation, volcano monitoring
• Time transfer: Precise time synchronization for critical infrastructure

Vital Points

• CORS networks provide continuous RTK corrections over wide areas
• National networks often free; commercial for premium services
• VRS technology creates a virtual base at your location
• Connect via NTRIP over cellular, straightforward to configure
• Accuracy 2–4 cm across well-designed networks
• Also valuable for science, weather, geophysics, space weather