> For the complete documentation index, see [llms.txt](https://docs.rtkdata.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rtkdata.com/integration-hub/gnss-rovers-and-receivers/emlid-reach-rs4.md).

# Emlid Reach RS4 / RS4 Pro RTK Setup: Emlid Flow

Set up the Emlid Reach RS4 and RS4 Pro with RTKdata NTRIP in Emlid Flow. Correction input, GGA, mountpoint AUTO, tilt compensation and fix rate tips.

The **Reach RS4** and **RS4 Pro** are Emlid's current all-band RTK receivers. They track L1, L2, L5 and L6 across 672 channels, carry an IMU for tilt compensation, run up to 16 hours on a charge, and are rated IP68 for use between -40 and +65 degrees C. Both work as base and as rover, and both are configured through the **Emlid Flow** app on iOS or Android.

For RTKdata the RS4 behaves exactly like the RS3 and the RS2+: corrections arrive over NTRIP through your phone's internet connection, so no local base is set up, levelled or re-surveyed.

## Requirements

* **Reach RS4 or RS4 Pro** powered on with a clear view of the sky
* **Emlid Flow app** on your phone or tablet (iOS or Android)
* **Internet connection** on the phone (cellular data or Wi-Fi)
* **RTKdata account** with active RTK credentials (username starts with `rtk`)
* **Survey pole** recommended, and required for tilt compensation calibration

{% hint style="info" %}
Don't have an RTKdata.com account yet? 👉 [Start 30-day Free Trial](https://rtkdata.com/try-rtk-corrections-free-for-30-days/) or [View Pricing](https://rtkdata.com/pricing/)
{% endhint %}

## Step-by-step setup

{% stepper %}
{% step %}

### Power on and connect in Emlid Flow

1. Hold the power button until the LEDs run through their startup sequence.
2. Open **Emlid Flow** and select your receiver, or tap **+ Add new device**.
3. Connect over **Wi-Fi** (the receiver creates a hotspot named `reach:XX:XX`) or over **Bluetooth** if you have paired before.
4. The device dashboard shows satellite count, solution status and battery level.

{% hint style="info" %}
If you already use an RS2+ or RS3, nothing here is new. The RS4 appears as a separate device in the list and the correction setup is identical.
{% endhint %}
{% endstep %}

{% step %}

### Open correction input

In Emlid Flow, open the **Correction input** tab, marked with the satellite dish icon. Select **NTRIP** and tap **+** to create a new profile.
{% endstep %}

{% step %}

### Enter your RTKdata connection settings

Select the tab for your region:

{% tabs %}
{% tab title="North America" %}

* **Host (domain):** `rtk.rtkdata.com`
* **Host (IP fallback):** `13.56.117.10`
* **Port:** `2101`
* **Username / Password:** From *RTK Credentials* in your [account dashboard](https://rtkdata.com/my-account/rtk-credentials/), not your website login
* **Mountpoint (ALL CAPS):** `AUTO` (recommended), or `AUTO_WGS84`, `AUTO_ITRF2020`, `AUTO_ITRF2014`
  {% endtab %}

{% tab title="Europe" %}

* **Host (domain):** `eu.rtkdata.com`
* **Host (IP fallback):** `3.73.41.96`
* **Port:** `2101`
* **Username / Password:** From *RTK Credentials* in your [account dashboard](https://rtkdata.com/my-account/rtk-credentials/), not your website login
* **Mountpoint (ALL CAPS):** `AUTO` (recommended), or `AUTO_WGS84`, `AUTO_ITRF2020`, `AUTO_ITRF2014`
  {% endtab %}

{% tab title="Australia" %}

* **Host (domain):** `aus.rtkdata.com`
* **Host (IP fallback):** `54.206.56.130`
* **Port:** `2101`
* **Username / Password:** From *RTK Credentials* in your [account dashboard](https://rtkdata.com/my-account/rtk-credentials/), not your website login
* **Mountpoint (ALL CAPS):** `AUTO` (recommended), or `AUTO_WGS84`, `AUTO_ITRF2020`, `AUTO_ITRF2014`
  {% endtab %}
  {% endtabs %}

Also set:

* **Send receiver position to the correction service: Enabled.** This sends NMEA GGA, which is how RTKdata knows where you are and which base station to use. Without it you get no corrections at all.

Tap **Save**.

{% hint style="warning" %}
`AUTO` covers the normal case. Pick a specific reference frame only when your project calls for one. The name is case sensitive, so enter it in **ALL CAPS**. A local coordinate system name is not a mountpoint and leaves you without corrections.
{% endhint %}
{% endstep %}

{% step %}

### Connect and wait for Fix

1. Tap **Connect** on the saved profile.
2. Correction input shows **Connected** with incoming bytes.
3. The solution status moves **Single**, then **Float**, then **Fix**.

Under clear sky, expect Fix within **15 to 60 seconds**.
{% endstep %}

{% step %}

### Calibrate tilt compensation

1. With an active Fix, mount the receiver on a survey pole.
2. In Emlid Flow, open **Settings > Tilt compensation**.
3. Enable it and follow the on-screen calibration.
4. Once calibrated, positions stay correct with the pole tilted, and the status bar shows the tilt indicator.
   {% endstep %}
   {% endstepper %}

## If your fix rate is lower than expected

This is the most common RS4 question we get, and it is almost never the correction stream.

* **Sky obstruction first.** Trees, buildings, vehicles and the person holding the pole all block satellites, especially at low elevation. A receiver that sees the whole sky fixes quickly and holds; one working next to a treeline does not.
* **Check the satellite count**, not just the status. Below roughly 12 tracked satellites, expect Float rather than Fix.
* **Check the age of corrections** in Emlid Flow. Above 5 seconds points at the phone's internet connection, not at the receiver or the network.
* **Distance to the base station** matters. Best results within 30 km, workable to about 50 km, unreliable beyond that.
* **Log raw data** under the Logging tab. If a site keeps fighting you, PPK on the logged file rescues the survey.

## Heights and coordinate systems

{% hint style="info" %}
RTKdata corrections deliver **ellipsoidal heights**, not orthometric heights above mean sea level. Use the **Global coordinate system** for the NTRIP connection, then apply your local datum and geoid in the project settings or in post-processing. See [Understanding Heights](/get-started/understanding-heights.md) and [Coordinate Systems & Datums](/get-started/coordinate-systems-and-datums.md).
{% endhint %}

## Troubleshooting

| Problem                                        | Cause                                                     | Fix                                                                                                                                                      |
| ---------------------------------------------- | --------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Correction input shows Disconnected            | Wrong credentials, or no internet on the phone            | Re-enter the username and password from *RTK Credentials*. The username starts with `rtk` and is not your website login.                                 |
| Connected, but the solution stays Single       | Position not being sent to the caster                     | Enable **Send receiver position to the correction service**. Without GGA the caster cannot assign a base station.                                        |
| Stuck on Float                                 | Sky obstruction, or the receiver is not upright on a pole | Move into open sky, check the satellite count, and see the fix rate section above.                                                                       |
| Mountpoint error                               | Lowercase or misspelled mountpoint                        | Type `AUTO` in ALL CAPS.                                                                                                                                 |
| "Confirm login to resume data sync"            | Emlid cloud sync prompt, unrelated to RTK                 | Confirm or dismiss it. Corrections keep flowing. If the popup drops the connection, tap **Reconnect**.                                                   |
| Connection drops repeatedly                    | Weak cellular signal                                      | Move to better coverage. The receiver reconnects automatically.                                                                                          |
| Corrections stop when a second device connects | Two devices on one set of credentials                     | One data stream allows one connection. See [Account & Credentials](/get-started/account-and-credentials.md#using-one-subscription-with-several-devices). |

## Tips

* **Wi-Fi for setup, Bluetooth in the field.** Bluetooth keeps the phone's own internet connection free for streaming corrections.
* **Running RS4 Pro as rover next to an RS2+ base** is a common setup. If the base pulls its own position from NTRIP at the same time, it needs its own data stream, otherwise the two devices disconnect each other.
* **Battery** lasts up to 16 hours, less with tilt compensation and constant streaming. A USB-C power bank covers long days.
* **UHF and LoRa radio** are available on the RS4 for local base and rover work. They are an alternative to NTRIP, not a supplement, so use one correction source at a time.

## Related Guides

* [Emlid Flow](/integration-hub/ntrip-clients-and-field-software/emlid-flow.md): the app used to configure every Emlid receiver, with correction input and project setup
* [Emlid Reach RS3](/integration-hub/gnss-rovers-and-receivers/emlid-reach-rs3.md): previous generation, same NTRIP profile and Emlid Flow workflow
* [Emlid Reach RS2+](/integration-hub/gnss-rovers-and-receivers/emlid-reach-rs2+.md): widely used mid-range rover, often paired with an RS4 as base
* [NTRIP & GGA Essentials](/integration-hub/ntrip-clients-and-field-software/ntrip-and-gga-essentials.md): how the AUTO mountpoint resolves to a base station once your position is sent
* [GNSS Rovers & Receivers](/integration-hub/gnss-rovers-and-receivers.md): all receiver guides and the universal NTRIP parameters

## Related Industry Solutions

* [Surveying](https://rtkdata.com/surveying/)
* [Construction](https://rtkdata.com/construction/)
* [Agriculture](https://rtkdata.com/agriculture/)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.rtkdata.com/integration-hub/gnss-rovers-and-receivers/emlid-reach-rs4.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.