How to Set Up an RTK Base Station and Connect to CORS
There are two ways to get RTK corrections: set up your own local base station, or connect to an existing CORS network via NTRIP. Local base setup involves positioning a base receiver over a known or approximate point, broadcasting corrections via UHF or LoRa radio to the rover. CORS connection involves configuring NTRIP credentials in your field controller to receive corrections over a cellular network — no physical base station required. This guide covers both, and how to decide which one fits your project.
1. Local Base Station vs CORS Network: Which Do You Need?
The primary factor in deciding between a local base station and a CORS network is the availability of accessible, reliable reference infrastructure in your project area.
When public or private CORS coverage is available with reliable cellular reception, connecting via NTRIP is generally faster and more convenient. It eliminates the need to transport, set up, and guard a separate base station on site, enabling single-operator field surveying.
When working in remote areas, mining corridors, agricultural tracts, or developing regions lacking operational CORS networks, deploying a local physical base station is the only dependable method to achieve centimeter-level positioning.
Both workflows utilize the exact same rover hardware. The only difference is the communication channel used to receive differential corrections: internal radio (UHF/LoRa) from a local base, or cellular internet (NTRIP) from a CORS server.
2. Setting Up a Local Base Station
Choose a secure, elevated location with an unobstructed 360-degree view of the sky. Setting up over a verified geodetic benchmark is ideal. In unmapped territory without known points, log an autonomous position or use satellite-delivered PPP/HAS corrections to establish baseline coordinates.
Secure the base receiver onto a heavy-duty tripod equipped with a tribrach and optical plummet. Carefully level the instrument using the plate vial, then measure and record the precise antenna height (true vertical or slant height) to the antenna reference point.
Open ApekSurv field software on your controller, connect to the base receiver via Bluetooth, and configure the internal radio protocol (e.g., Transparent / TT450S / LoRa), frequency channel, and output power. Set the correction message format to RTCM 3.2.
Start the base broadcast. Check the receiver screen or LED status indicators to verify that the receiver is tracking satellites (15+ recommended) and the Tx (transmission) light is flashing steadily at 1 Hz.
Switch the controller connection to the rover receiver, match the radio channel and baud rate to the base, and verify that the rover locks onto differential corrections to achieve a stable Fixed solution within 30 seconds.
3. Connecting to a CORS Network via NTRIP
Acquire valid account credentials from your CORS network provider, including the caster host IP address (or domain URL), port number, mount point identifier, username, and password.
In ApekSurv, navigate to the rover network configuration menu. Select Internal 4G or Controller Internet as the data link, choose NTRIP as the protocol, and enter your server IP, port, and account credentials.
Ensure the controller or receiver SIM card has an active mobile data subscription and a stable cellular signal on site to maintain an uninterrupted data stream.
Select the appropriate mount point (such as a single nearest physical station or a networked VRS/MAC stream), connect to the NTRIP caster, and verify that the solution transitions to Fixed within 30 seconds.
4. Verifying Your Setup: Checking Fixed Solution
Regardless of whether you deploy a local base station or connect to a CORS network, always verify your positioning solution before recording project points or staking out lines.
Perform a check shot over a known secondary control monument or site benchmark. Verify that the horizontal and vertical coordinate residuals match design tolerances (typically within ±20mm to ±30mm).
Ensure that the field controller status bar clearly displays "FIX", horizontal and vertical RMS values reflect millimeter/centimeter precision, and the receiver maintains solid multi-constellation satellite tracking (15+ satellites recommended).
5. Common Setup Mistakes
Symptom: The rover tracks satellites normally but remains permanently in Single autonomous mode without receiving differential data packets.
Cause: The base station and rover are set to conflicting radio channels, frequencies, or air baud rates.
Fix: Open the internal radio settings in ApekSurv for both instruments and verify that the channel number, frequency (MHz), protocol, and baud rate match identically.
Symptom: The field software attempts to connect to CORS but immediately drops the connection or displays an authentication error.
Cause: Typographical errors in the server IP, port number, mount point name, or case-sensitive username and password.
Fix: Carefully re-enter credentials provided by your CORS administrator, paying close attention to character casing and trailing spaces, then refresh the source table to select the correct mount point.
Symptom: Coordinates drift gradually over the course of a multi-hour survey session, introducing systematic errors into stakeout points.
Cause: The base tripod was set up on soft soil, hot asphalt, or near heavy vibrating machinery, causing physical settlement or tilt.
Fix: Set up on firm, compacted ground or concrete pads. Firmly press the tripod shoes into the ground, tighten all leg clamps securely, and verify the optical plummet level after setup.
6. FAQ
Do I need a local base station if my area has CORS coverage?
No. If your project site has accessible CORS coverage and reliable cellular reception, you can connect your rover directly via NTRIP without transporting, setting up, or guarding a physical base station on site.
How long does it take to get Fixed after connecting to CORS?
Under clear sky conditions with a modern multi-constellation GNSS receiver, obtaining an RTK Fixed solution via NTRIP typically takes less than 30 seconds after establishing the data connection.
What information do I need to connect to a CORS network?
You need the NTRIP caster host IP address or domain URL, port number, mount point identifier, and your authorized user account credentials (username and password).
Can the same rover work with both a local base and CORS?
Yes. Modern GNSS rovers support seamless switching between receiving internal radio corrections from a local base (UHF/LoRa) and receiving network corrections from a CORS caster via internal 4G or controller Wi-Fi/cellular.
LOCAL BASE OR CORS. ONE SYSTEM, EITHER WAY.
APEKS RTK GNSS receivers support both local Base+Rover setup and NTRIP CORS connection — switch between them depending on your project's network coverage. IP67/IK08. 120° IMU.
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