Troubleshooting Guide for CORS Mode in GNSS Surveying

The data collector or receiver shows no network icon. The device cannot retrieve a Mountpoint list, and status remains offline.

SIM card not inserted, insufficient data balance, poor contact, or the receiver's internal modem has not initialised correctly.

1. Check SIM card seating. Verify whether the SIM is installed in the receiver or the data collector, depending on your model. Remove and reinsert the card, ensuring the gold contacts face the correct direction and the card clicks into place.
2. Verify data plan status. Call the carrier or check the account management portal to confirm the SIM has an active data plan and has not been suspended for exceeding limits. Many survey SIMs are prepaid — a zero balance blocks all data traffic.
3. Isolate the receiver from the SIM. If your data collector supports a mobile hotspot, connect the receiver via Wi-Fi to rule out the SIM as the failure point. If the receiver works on Wi-Fi but not on its internal SIM, the SIM or the receiver's modem slot is the culprit.
4. Restart both devices. Power cycle the receiver and the data collector. Some GNSS receivers require a full restart after a SIM change before the modem negotiates a carrier connection.

The network icon is active, but the Mountpoint list never loads. The NTRIP client reports a connection timeout or "server unreachable" error.

Incorrect IP address or port number, case sensitivity in the server address, carrier-level firewall blocking the port, or the CORS server is temporarily offline.

1. Double-check IP address and port. Re-type the server IP and port manually. Pay close attention to periods, colons, and the absence of leading or trailing spaces. Some CORS providers use hostnames instead of IP addresses — confirm you have the correct domain.
2. Test server reachability. From a laptop or phone on the same cellular network, open a terminal and ping the server address. A successful ping but failed NTRIP connection suggests the port is blocked.
3. Switch network type. If you are using 4G, try a Wi-Fi network. If Wi-Fi works, the mobile carrier may be blocking the specific port your CORS provider uses. Common NTRIP ports include 2101, 8080, and 80 — some carriers restrict non-standard ports on consumer data plans.
4. Confirm server status. Contact your CORS provider directly. Regional CORS networks occasionally go offline for maintenance. Many providers post service status updates on their websites or send alerts to registered users.

The Mountpoint list loads successfully, indicating the server is reachable, but authentication is rejected when you enter your username and password.

Expired account, incorrect password casing, invisible characters from copy-paste, or the account is already bound to another device's unique identifier.

1. Re-type credentials manually. Avoid copying and pasting from emails or documents. Hidden trailing spaces and non-printing characters are a common source of failed logins. Type the username and password character by character.
2. Confirm account expiry date. Many CORS subscriptions are annual or monthly. Check with the provider whether the account is still active. Some providers allow you to verify status through a web portal.
3. Check device binding. Some CORS networks lock an account to the first device serial number or IP address that authenticates. If you have moved the SIM to a new receiver or changed data collectors, the server may reject the login. Ask the provider to release the device lock.
4. Request a test account. Most CORS support teams can generate a temporary test login for 24–48 hours. If the test account works, the problem is definitively with your original credentials.

The data collector shows a successful NTRIP connection and the Mountpoint is selected, but the status indicator remains "Single" or "Float" — never reaching "Fixed." All on-screen indicators suggest a functioning connection, yet no centimetre-level solution appears.

A. Insufficient satellite count. A GNSS receiver needs at least 20 effective satellites tracked across multiple constellations to initialise an RTK fixed solution reliably. If the satellite count dips below this threshold, the receiver cannot resolve integer ambiguities. Move to an area with full sky visibility — overhead tree canopy, building walls within 30 metres, and high-voltage power lines all degrade signal quality even when satellite counts appear adequate.

B. No differential data despite login. A successful NTRIP login does not guarantee data is flowing. Check that you have selected the correct Mountpoint — Mountpoints are often named by region or nearest reference station; selecting a node 200 kilometres away will not deliver usable corrections. Also verify which device is managing the NTRIP connection: if your receiver has an internal modem, the data collector should not run a second NTRIP client simultaneously. Two competing correction streams can cause the rover to reject both.

C. Distance to nearest reference station exceeds network limits. Most CORS networks guarantee reliable fixed solutions within 50–70 kilometres of a physical reference station. Beyond this distance, atmospheric decorrelation reduces correction accuracy. Pull up the CORS network coverage map for your region and confirm your job site falls within the shaded coverage polygon.

D. Multipath interference or obstructed sky view. Reflective surfaces — metal roofs, chain-link fences, water bodies, glass facades — create multipath signals that confuse the receiver's ambiguity resolution engine. If the satellite count is high but the solution oscillates between Float and Single, reposition the rover 3–5 metres away from any reflective surface. Allow 2–3 minutes after repositioning for the receiver to restart initialisation with clean signals.

E. Incorrect coordinate system or datum mismatch. If the CORS network transmits corrections in ITRF2014 but your project is configured for NAD83(2011), the software may refuse to display Fixed even though the underlying RTK engine has resolved ambiguities. Confirm that the project coordinate system and geoid model match the datum broadcast by the CORS network. Country reference: Indonesia uses DGN95; Saudi Arabia uses GCS-80; South Africa uses Hartebeesthoek94; Brazil uses SIRGAS2000.

The receiver achieves a fixed solution with expected RMS values, but after 10–15 minutes the status drops to Float or Single. The cycle may repeat after a manual reconnect.

This pattern almost always points to network instability rather than satellite geometry. The correction data stream experiences a momentary interruption, the receiver loses integer ambiguity lock, and the NTRIP client does not reinitialise cleanly.

1. Check data latency. In your NTRIP client or data collector software, look for a latency or age-of-correction indicator. Latency above 3 seconds can degrade RTK performance. Consistent spikes above 5 seconds suggest network congestion or a weak cellular signal.
2. Verify SIM data throttling. Some prepaid or low-cost data plans throttle bandwidth after a daily data cap is reached. CORS correction data is low volume but requires a steady, uninterrupted stream. A throttled connection introduces gaps that break the fixed solution.
3. Enable auto-reconnect. Most NTRIP client software includes an auto-reconnect setting. If the correction stream drops momentarily, the client should attempt to reconnect to the Mountpoint and reinitialise. Without this enabled, a 2-second drop can permanently break the fixed solution until you intervene manually.
4. Eliminate Wi-Fi handoff interruptions. If the data collector is connected to a site Wi-Fi network with multiple access points, roaming between them can cause momentary disconnects. Use a single hotspot or the receiver's internal 4G modem to maintain a stable connection path.