> For the complete documentation index, see [llms.txt](https://help.felt.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.felt.com/field-app/gnss-receivers.md). # GNSS receivers Get submeter to centimeter-level positions in the Field App by pairing a Bluetooth GNSS or GPS receiver with your iPhone, iPad, or Android device. If your team uses professional-grade Global Navigation Satellite System (GNSS) hardware, pair the receiver with your phone or tablet over Bluetooth for submeter to centimeter-level positions. If the receiver supplies location data to the operating system, the Field App uses it automatically, both for location tracking and when you place points or vertices at your location. See [Capture field data](/field-app/collect-field-data.md). On iPhone and iPad, the receiver must be certified for Apple's MFi (Made for iPhone/iPad) program to supply the location. Receivers without MFi certification, such as raw u-blox boards and many do-it-yourself real-time kinematic (RTK) kits, can't supply a location on iOS. On Android, most Bluetooth receivers that output NMEA sentences work: the receiver's companion app, or another NMEA app, supplies the location as a mock location provider. To confirm that a receiver is compatible, check with its manufacturer. ## Set up a receiver on iOS On iOS, you pair the receiver in your device's Bluetooth settings, and iOS passes its position to the Field App. 1. Turn on the receiver and put it in Bluetooth pairing mode. See the receiver's manual. 2. On your iPhone or iPad, open **Settings** > **Bluetooth**, then tap the receiver's name to pair it. 3. Optional: Set up real-time corrections in the receiver's companion app. See [Set up real-time corrections](#set-up-real-time-corrections). 4. Open the Field App and turn on location tracking. The Field App uses the receiver's position. ## Set up a receiver on Android On Android, a companion app connects to the receiver and passes its position to the operating system as a mock location. Set up the mock location provider once in Android's developer options. The option names vary by device manufacturer. 1. Turn on the receiver and pair it in your device's Bluetooth settings. 2. Install an app that can provide a mock location: the receiver manufacturer's companion app or a third-party NMEA app. 3. Turn on developer options: open **Settings** > **About phone**, and tap **Build number** seven times. 4. Open **Settings** > **Developer options**, tap **Select mock location app**, and select the app from step 2. 5. In the companion app, connect to the receiver and check that the app receives positions from it. 6. Optional: Set up real-time corrections in the companion app. See [Set up real-time corrections](#set-up-real-time-corrections). 7. Open the Field App and turn on location tracking. The Field App uses the receiver's position. Leave the companion app running in the background while you capture data. ## Set up real-time corrections RTK corrections can improve a GNSS receiver's accuracy from meter-level to centimeter-level, using a base station or a correction network. Networks often deliver them over the internet with NTRIP (Networked Transport of RTCM via Internet Protocol). Felt doesn't manage correction sources. Set up corrections in the receiver manufacturer's companion app before you start capturing data, and keep the app running. For example, Trimble receivers use Trimble Mobile Manager, Emlid receivers use Emlid Flow, and Eos receivers use Eos Tools Pro. The corrected position reaches the Field App through the operating system, with no settings to change in Felt. ## Check your accuracy in the Field App The Field App shows the accuracy of your current position, so you can confirm that the app is using your GNSS receiver. 1. Open a map in the Field App and turn on location tracking. 2. Tap the **+** button, then start adding a feature. Your location's accuracy appears at the top of the screen. 3. Tap the accuracy to open **GPS Details**, and check **Location accuracy**. If **Location accuracy** is no better than your phone's usual accuracy of a few meters, check the receiver's connection in its companion app. The Field App doesn't save the accuracy of each point. To keep an accuracy value, add an attribute to the layer's form, and enter the value from **GPS Details**. See [Forms](/layers/forms.md). --- # 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 by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://help.felt.com/field-app/gnss-receivers.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.