Connect RTK FIX to Emlid Reach RS4 with Emlid Flow

Introduction #

This guide explains how to connect an Emlid Reach RS4 rover to an RTK correction service purchased through RTK FIX. The receiver is configured with the Emlid Flow application on an Android or iOS phone or tablet.

Emlid recommends connecting Emlid Flow to the Reach RS4 using Bluetooth. With this method, Emlid Flow can use the mobile device’s internet connection to deliver NTRIP corrections to the receiver.

The NTRIP connection and the project coordinate system are separate settings. Receiving corrections does not confirm that the correct coordinate system, datum or geoid is selected for your project.

RTK FIX gives you access to correction services from multiple providers through one platform. Choose coverage that matches your project location and equipment. Open the RTK FIX dashboard →

What you need #

• An Emlid Reach RS4 receiver.
• An Android or iOS phone or tablet with Bluetooth enabled.
• The latest available version of Emlid Flow.
• An active internet connection on the phone or tablet.
• An active RTK correction subscription purchased through RTK FIX.
• Your RTK FIX NTRIP address, port, username, password and mountpoint.
• A suitable survey pole, bipod or other stable mounting system.
• The correct project coordinate system, datum, geoid model and antenna height information.

For the manufacturer’s receiver instructions, see the Emlid Reach RS4 and RS4 Pro documentation →.

Find your RTK FIX NTRIP credentials #

1. Open Open the RTK FIX dashboard →.
2. Sign in to your RTK FIX account.
3. Open the active correction subscription for your project area.
4. Locate the NTRIP connection details supplied for that subscription.
5. Keep the address, port, NTRIP username, NTRIP password and mountpoint available while configuring Emlid Flow.

The NTRIP username and password are not necessarily the same as your RTK FIX website login. NTRIP credentials may be case-sensitive and must be copied exactly. Never enter the example placeholders from this guide as real credentials.

Connect the receiver #

1. Place the Reach RS4 outside where it has a clear view of the sky.
2. Press and hold the receiver’s power button for approximately five seconds.
3. Wait for the receiver to complete its startup sequence.
4. Enable Bluetooth and mobile data or Wi-Fi internet on the phone or tablet.
5. Open Emlid Flow.
6. Allow the Bluetooth, local network and notification permissions requested by the application. The exact permissions depend on the operating system version.
7. Select the Reach RS4 from the list of available receivers.
8. Wait until Emlid Flow shows that it is connected.

Bluetooth is the manufacturer-recommended connection method for this NTRIP workflow. Emlid Flow uses the phone or tablet’s internet connection to provide corrections to the receiver.

On Android, disable battery optimisation for Emlid Flow when necessary. Battery optimisation can interrupt the application or the correction connection while working in the field.

Open the NTRIP settings #

1. In Emlid Flow, open Settings.
2. Select GNSS settings.
3. Set Positioning mode to Kinematic.
4. Confirm that the required satellite systems are enabled.
5. Tap Apply.
6. Open the Correction input screen.
7. In the NTRIP section, select the option that uses the mobile device’s internet connection.

On current Android versions of Emlid Flow, this option may be labelled NTRIP via mobile device. On other versions, including some iOS releases, it may appear as Internet over mobile device. Use the option that clearly states that corrections will be received through the phone or tablet rather than through the Reach receiver.

1. Tap Add profile.

Enter the RTK FIX connection details #

Enter the connection details exactly as shown in your RTK FIX dashboard.

Device or app field	What to enter
Address	The NTRIP caster address supplied in your RTK FIX subscription details, without adding spaces or changing the spelling.
Port	The NTRIP port supplied in your RTK FIX subscription details.
Username	Your RTK FIX NTRIP username, for example your-ntrip-username. Do not automatically use your website login email address.
Password	Your RTK FIX NTRIP password, for example your-ntrip-password.
Mount Point	The mountpoint assigned to or selected for your RTK FIX subscription.
Send receiver’s position to the provider	Enable this option when the selected mountpoint uses VRS or another network method that requires the rover position.

Do not assume that the default port shown by Emlid Flow is correct. Always use the port displayed in the RTK FIX dashboard.

VRS services commonly require the rover to send NMEA GGA position messages to the correction provider. In Emlid Flow, this is controlled by Send receiver’s position to the provider. No manual GGA interval is required unless your correction provider gives a verified product-specific instruction.

Select the mountpoint #

1. Tap the Mount Point field.
2. Select the mountpoint supplied for your RTK FIX subscription.
3. When several mountpoints are available, choose the one specified for your region, network type and required correction format.
4. For a VRS mountpoint, enable Send receiver’s position to the provider.
5. Do not select a mountpoint only because its name appears geographically close. Confirm that it is included in your subscription and suitable for your project.

A physical reference-station mountpoint is normally selected according to its coverage and distance from the work area. A VRS or network mountpoint uses the receiver’s approximate position to generate or select suitable corrections.

Start the NTRIP connection #

1. Check the address, port, username, password and mountpoint once more.
2. Tap Save.
3. Return to the Correction input screen if Emlid Flow does not return automatically.
4. Select the saved RTK FIX NTRIP profile.
5. Keep Emlid Flow open and maintain the Bluetooth and internet connections.
6. Wait while the receiver connects to the caster and begins receiving correction data.

Emlid Flow may initially show Waiting for corrections. This status should change after the receiver has internet access, valid credentials, a compatible mountpoint and sufficient satellite visibility.

Working in several regions or with different network requirements? RTK FIX lets you manage correction services from multiple providers through one dashboard. Open the RTK FIX dashboard →

Verify the RTK solution #

The current solution status is shown in the upper-right area of Emlid Flow. It can also be reviewed on the application’s Status screen.

Status	Meaning
Single or Autonomous	The receiver is calculating its position from satellite observations without applying usable RTK corrections. Accuracy is normally at the metre level.
DGPS or DGNSS	Differential corrections are being applied, but the receiver does not have an RTK ambiguity-fixed solution. This is not an RTK Fixed result.
FLOAT	The receiver is receiving RTK corrections, but the carrier-phase ambiguities have not been fully resolved. Float must not be treated as centimetre-accurate.
FIX or Fixed	The receiver has resolved the RTK ambiguities and is reporting an RTK fixed solution. Confirm the reported accuracy and all project settings before measuring.

Measure only after Emlid Flow shows FIX and the estimated horizontal and vertical accuracy are acceptable for the work. The time required to obtain FIX depends on satellite visibility, correction quality, distance to the reference network, atmospheric conditions and the surrounding environment.

Checks before measuring #

• Confirm that the solution status is FIX.
• Confirm that the reported horizontal and vertical accuracy meet the project requirements.
• Check that correction data is still being received and that the correction age is acceptable.
• Verify the selected project coordinate system separately in Emlid Flow.
• Verify the horizontal datum, vertical datum and geoid model required by the project.
• Enter the correct pole or antenna height and confirm how the application expects that height to be measured.
• Keep the pole stable and correctly levelled unless a verified tilt-compensation workflow is being used.
• Maintain a clear view of the sky. Emlid recommends avoiding obstacles within approximately 30 degrees above the horizon.
• Keep away from buildings, trees, vehicles and other objects that can block or reflect satellite signals.
• Check the measured position against a known control point when the project procedure requires it.

NTRIP configuration controls the correction connection. Project coordinates, datum transformations, geoid models and antenna-height settings must be configured and verified separately. Receiving corrections does not prove that the recorded coordinates are in the correct reference system.

Troubleshooting #

Problem	Possible cause	Solution
Emlid Flow cannot find the Reach RS4	Bluetooth is disabled, permissions were refused or the receiver has not completed startup.	Enable Bluetooth, grant the requested Emlid Flow permissions, restart the receiver if necessary and select it again from the receiver list.
The receiver connects, but NTRIP does not start	The phone or tablet does not have a working internet connection.	Open a website or another online service to test the mobile device’s connection, then return to Emlid Flow.
Waiting for corrections remains visible	The caster address, port, username, password or mountpoint is incorrect.	Compare every field with the RTK FIX dashboard. Copy case-sensitive credentials exactly and remove accidental spaces.
Authentication fails	The RTK FIX website login was entered instead of the NTRIP username and password.	Use the separate NTRIP credentials shown for the active correction subscription.
The mountpoint list is empty	The caster cannot be reached or the login details are invalid.	Check internet access, address, port and NTRIP credentials. Confirm that the subscription is active.
A VRS mountpoint connects but no corrections are received	The service is not receiving the rover’s approximate position.	Enable Send receiver’s position to the provider and reconnect the profile.
The solution remains Single	Corrections are not being received or cannot be used.	Check the active NTRIP profile, internet connection, correction status and mountpoint compatibility.
The solution remains FLOAT	Satellite visibility is restricted, signals are affected by multipath or correction quality is insufficient.	Move to an open area, keep the receiver away from buildings and trees, stabilise the pole and recheck the correction stream.
The NTRIP connection stops when the screen is locked	The operating system is restricting Emlid Flow in the background.	Disable battery optimisation or background restrictions for Emlid Flow and keep Bluetooth and internet access enabled.
FIX is shown, but coordinates do not match the project	The wrong coordinate system, datum, geoid model, transformation or antenna height is selected.	Review the project coordinate settings and antenna height separately. Do not change the NTRIP credentials to correct a coordinate-system problem.
The position changes unexpectedly near buildings or trees	Satellite signals are blocked or reflected by nearby obstacles.	Move to a location with a clearer sky view and confirm FIX and acceptable reported accuracy before measuring.
Correction age is high	The internet connection or correction stream is delayed or unstable.	Check mobile coverage, keep Emlid Flow active and reconnect the NTRIP profile. Do not measure while correction data is stale.

Need help? #

First, confirm that the Reach RS4 is connected to Emlid Flow, the mobile device has internet access, the RTK FIX subscription is active and all NTRIP fields match the dashboard exactly.

For receiver menus, firmware and application behaviour, consult the official Emlid Reach RS4 NTRIP instructions →.

For other receiver and application combinations, visit View all RTK FIX setup guides →.