> For the complete documentation index, see [llms.txt](https://docs.premium-positioning.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.premium-positioning.com/guides/topcon-x35-xd+-agi-4-ags-2.md).

# Topcon X35 / XD+ (AGI-4 / AGS-2)

These steps connect a Topcon X35 / XD+ (AGI-4 / AGS-2) to the Premium Positioning correction network over NTRIP, using Horizon. They assume you already have your NTRIP credentials.

### Before you start

* Your NTRIP username and password, from your Premium Positioning welcome email or your account on the customer portal.
* Horizon.
* A working internet connection on the controller or phone.
* A clear view of the sky at the point you are measuring.

### Network settings

These are the same for every Premium Positioning customer. Only your username and password are unique to you.

* Server or host: rtkpremium.xyz
* Port: 2101
* Mountpoint: COMMON
* Protocol: NTRIP

### Steps

1. Confirm your hardware is RTK-ready: On the X35 / XD+ console (Horizon) with an AGI-4 or AGS-2 receiver, Network RTK / NTRIP requires the receiver unlocked for RTK and a working internet connection (the AGI-4 normally needs the RTK/IMU unlock plus an internal cellular SIM or an approved Wi-Fi/cellular modem). If unsure your unit is RTK-enabled, check with Premium Positioning first.
2. Open the GPS Correction setup screen: From the Horizon home screen open the menu and go to System > GPS > Correction. This opens the GPS Correction Source screen (the GPS section is under System, correction options under it).
3. Set the Correction Source to RTK (NTRIP): Tap CORRECTION SOURCE and change it from Autonomous to RTK (NTRIP). Wording may read 'RTK', 'NTRIP' or 'RTK (NTRIP)' by firmware - choose the option for Network RTK over the internet (NTRIP).
4. Let the modem / connection wizard run: When RTK (NTRIP) is selected, Horizon runs a short wizard to detect the modem or cellular/Wi-Fi connection. Allow it to finish. If it can't find a connection, confirm your SIM/data plan or Wi-Fi modem is active, then retry.
5. Open the NTRIP Setup screen: After the wizard, Horizon shows the NTRIP Setup screen (also under System > GPS, NTRIP tab). Enter the caster details on the right, and (if using a receiver SIM) the GSM/APN details on the left.
6. Enter the NTRIP Address (caster host): Tap NTRIP ADDRESS and enter exactly: rtkpremium.xyz (no http\://, no spaces). Sometimes called the caster, server or end point.
7. Enter the NTRIP Port: Tap NTRIP PORT and enter: 2101
8. Enter the NTRIP Mount Point: Tap NTRIP MOUNT POINT and enter: COMMON (capitals). If your firmware can fetch the source table, select COMMON from the list.
9. Enter YOUR NTRIP Username: Tap NTRIP USERNAME and enter the username from your welcome email - your own personal login, case-sensitive.
10. Enter YOUR NTRIP Password: Tap NTRIP PASSWORD and enter the password from your welcome email, exactly (case-sensitive). Premium Positioning never sets these for you - they are unique to your account.
11. Set the cellular / data details if using a SIM: If the receiver connects through its own SIM rather than Wi-Fi, fill the GSM fields on the left (GSM APN is the key one - your carrier's APN; GSM USERNAME/PASSWORD/PIN only if required; ALLOW 3G/roaming as appropriate). If you connect via Wi-Fi or the console's data link, leave the GSM fields as they are.
12. Save and let the connection establish: Close the NTRIP Setup screen to save. Horizon dials the caster and starts streaming. The receiver needs a standalone position first to send its location, so give it clear sky and a minute or two.
13. Confirm an RTK Fixed solution: Check the GPS/correction status (the satellite/GPS icon in the top status bar, or System > GPS status). Wait until it reports RTK Fixed ('Fixed', 'RTK Fix' or 'RTK Integer') - cm-level accuracy. If it stays on 'Float', 'DGPS', 'Autonomous' or 'No correction', recheck the caster details, mount point, your username/password, and that you have live internet and open sky.

### If the fix will not hold

Network RTK over NTRIP needs live internet on the receiver/console (cellular SIM, Wi-Fi or modem) and open sky. Menu wording, the correction-type label and the fix-status text differ slightly between Horizon firmware versions and between X35 and XD+ - if a label differs, choose the equivalent (Network RTK / NTRIP over the internet).

For more, see RTK corrections troubleshooting and Fix inconsistent RTK accuracy on site.

### Need help

Support is available 24/7. Include your receiver model, the mountpoint, the solution status, and the correction age when you get in touch.