> 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/external-gnss-receivers.md). # External GNSS receivers The Field App works with external high-accuracy GPS and GNSS receivers on both iOS and Android, giving field teams submeter to centimeter-level positioning for data collection, asset mapping, and inspections. If your organization uses professional-grade GNSS hardware, this page explains how it connects to Felt and what to expect on each platform. ## How it works The Field App receives location data from your mobile device's operating system. When you pair an external GNSS receiver via Bluetooth, the receiver's high-accuracy position replaces the device's built-in GPS. The Field App then uses that improved position for all data collection, feature placement, and location tracking — no additional configuration is needed inside Felt. This means Felt is compatible with a wide range of Bluetooth GNSS receivers from leading manufacturers. If your receiver provides location data through the standard platform location services (Core Location on iOS, Location Services on Android), the Field App will use it automatically. ## Supported GNSS receivers on iOS On iOS, Bluetooth GNSS receivers must be part of Apple's MFi (Made for iPhone/iPad) program to provide location data to apps through Core Location. The following MFi-certified receivers are compatible with the Field App on iPhone and iPad: **Eos Positioning Systems** * Eos Arrow Lite * Eos Arrow 100 / Arrow 100+ * Eos Arrow 200 * Eos Arrow Gold / Arrow Gold+ * Eos Skadi **Bad Elf** * Bad Elf Flex * Bad Elf Flex Mini * Bad Elf GNSS Surveyor * Bad Elf GPS Pro+ * Bad Elf GPS Pro * Bad Elf GPS for Lightning Connector **Trimble** * Trimble R1 * Trimble R2 * Trimble R580 * Trimble R780 / R780-2 * Trimble R980 * Trimble R10 Model 2 * Trimble R12 / R12i * Trimble Catalyst DA2 * Trimble TDC600 / TDC650 **Emlid** * Emlid Reach RX MFi (MFi-certified batches only; check for the Made for Apple badge on the packaging) * Emlid Reach RX2 * Emlid Reach RS4 / RS4 Pro **Juniper Systems** * Juniper Geode GNS3H * Juniper Geode GNS3M * Juniper Geode GNS3S **Geneq** * Geneq SXblue II * Geneq SXblue III **Leica Geosystems** * Leica Zeno GG04 plus * Leica FLX100 plus **Other** * Garmin GLO / GLO 2 * Dual XGPS160 * SparkPNT TX2 / Facet FP * Asteri X1i {% hint style="info" %} Non-MFi receivers (such as raw u-blox boards, ArduSimple, or SparkFun RTK kits) cannot provide location data to iOS apps through Core Location. If your receiver is not MFi-certified, it will not work with the Field App on iPhone or iPad. {% endhint %} ## Supported GNSS receivers on Android On Android, the Field App works with virtually any Bluetooth GNSS receiver that outputs NMEA sentences, when configured as a mock location provider. This includes all of the receivers listed above for iOS, plus many additional devices. Android receivers that have been widely used for field data collection include: * Eos Arrow Lite, Arrow 100, Arrow 100+, Arrow 200, Arrow Gold, Arrow Gold+, Skadi * Bad Elf Flex, Flex Mini, GNSS Surveyor, GPS Pro+, GPS Pro * Trimble R1, R2, R580, R780, R780-2, R8s, R980, R10, R10 Model 2, R12, R12i, Catalyst DA2, TDC600, TDC650 * Emlid Reach RX, Reach RX2, Reach RS2+, Reach RS4, Reach RS4 Pro * Juniper Systems Geode GNS3H, GNS3M, GNS3S * Leica GG03, GG04, GG04 plus, FLX100, FLX100 plus * Geneq SXblue II, SXblue III * Spectra Precision SP30, SP60, SP80, SP85, SP100 * Carlson BRx6+ * Sokkia GCX3 * Garmin GLO * Dual XGPS150A, XGPS160 * SparkFun RTK Facet, RTK Express, RTK Surveyor * ArduSimple simpleRTK2B, simpleRTK3B (via Bluetooth Serial Port Profile) {% hint style="success" %} This is not an exhaustive list. If your receiver outputs NMEA0183 sentences and can be configured as a mock location provider on Android, it should work with the Field App. {% endhint %} ## Setting up your receiver ### iOS setup 1. **Turn on your receiver** and make sure it is in Bluetooth pairing mode. Refer to your receiver's user manual for instructions. 2. **Open your device's Bluetooth settings** (Settings > Bluetooth) and wait for the receiver to appear in the list of available devices. 3. **Tap the receiver name** to pair it. Once paired, iOS will automatically use the receiver's position through Core Location. 4. **Open the Field App** and begin collecting data. No additional configuration is needed inside Felt — the app will use the receiver's high-accuracy location. {% hint style="info" %} Some receivers require a companion app to configure correction sources (NTRIP, RTK networks) before the receiver can deliver high-accuracy positions. For example, Trimble receivers require Trimble Mobile Manager, Emlid receivers use Emlid Flow, and Eos receivers use Eos Tools Pro. Set up your corrections in the manufacturer's companion app before beginning data collection in Felt. {% endhint %} ### Android setup Android requires a few extra steps to route external GNSS data to apps through the operating system. 1. **Pair your receiver** in your device's Bluetooth settings, just as you would on iOS. 2. **Install a companion or helper app** that connects to your receiver and provides its location to Android as a mock location source. Options include: * Your receiver manufacturer's companion app (Eos Tools Pro, Trimble Mobile Manager, Emlid Flow, Geode Connect, SXblue Toolbox) * A third-party NMEA app such as Bluetooth GPS, Lefebure NTRIP Client, or GNSS Master 3. **Enable Developer Options** on your Android device. Go to Settings > About Phone and tap Build Number seven times to unlock Developer Options. 4. **Set the mock location app.** In Settings > Developer Options, find "Select mock location app" (or "Allow mock locations" on older devices) and choose the app from step 2. 5. **Connect and verify** in the companion app that you are receiving positions from the external receiver. 6. **Open the Field App** and begin collecting data. Felt will now receive the high-accuracy position from your external GNSS receiver. {% hint style="success" %} If your receiver needs real-time corrections (RTK or NTRIP), configure the correction source in the companion app before opening Felt. The companion app typically runs in the background while you collect data. {% endhint %} ## Configuring real-time corrections (RTK / NTRIP) Many high-accuracy GNSS receivers support real-time kinematic (RTK) positioning through NTRIP correction services. RTK corrections can improve your position accuracy from meter-level to centimeter-level. Felt does not manage correction sources directly. Configure your RTK or NTRIP connection through your receiver manufacturer's companion app: | Receiver | Companion app | Platform | | ------------------------------ | ---------------------- | ------------ | | Eos Arrow series | Eos Tools Pro | iOS, Android | | Trimble R-series, Catalyst DA2 | Trimble Mobile Manager | iOS, Android | | Emlid Reach RX / RS series | Emlid Flow | iOS, Android | | Bad Elf Flex / GNSS Surveyor | Bad Elf app | iOS, Android | | Juniper Geode | Geode Connect | iOS, Android | | Geneq SXblue | SXblue Toolbox | iOS, Android | | Leica GG04 / FLX100 | Leica Zeno Connect | iOS, Android | Once the companion app is configured and streaming corrections, the improved position flows through to the Field App automatically. ## Frequently asked questions **Do I need to change any settings in the Field App to use an external receiver?** No. The Field App receives location from your device's operating system. When an external GNSS receiver is paired and providing location data, the Field App uses it automatically. **Can I use the receiver manufacturer's companion app at the same time as Felt?** Yes. On both iOS and Android, the companion app runs in the background while you collect data in the Field App. This is the recommended setup when using RTK corrections. **What if my receiver isn't on the list?** On Android, any Bluetooth GNSS receiver that outputs NMEA sentences and can act as a mock location provider should work. On iOS, the receiver must be MFi-certified to provide location data through Core Location. Contact if you have questions about a specific receiver. **Does this work with the Felt web app in a mobile browser?** The external receiver's position is shared with all apps on the device that use the operating system's location services. If you access Felt through a mobile browser that uses the device's location, the high-accuracy position should be available. For the best field data collection experience, we recommend using the Field App. **Which receivers support differential corrections (SBAS, RTK, PPP)?** Most professional-grade GNSS receivers support some form of differential correction. Consumer-grade receivers like the Garmin GLO and Bad Elf GPS Pro support SBAS (free, meter-level corrections). Survey-grade receivers like the Eos Arrow Gold, Trimble R12i, Emlid Reach RX, and Juniper Geode GNS3 support RTK (centimeter-level corrections through a subscription or base station). Refer to your receiver manufacturer's documentation for correction capabilities. **What accuracy can I expect?** Accuracy depends on your receiver, correction source, and field conditions. Approximate ranges: | Receiver type | Correction | Typical accuracy | | ------------------------------------------------------------------ | ----------- | ---------------- | | Device built-in GPS | None | 3–5 meters | | Consumer Bluetooth GPS (Garmin GLO, Bad Elf GPS Pro) | SBAS / WAAS | 1–3 meters | | Mapping-grade GNSS (Eos Arrow Lite, Emlid Reach RX, Juniper Geode) | SBAS | Sub-meter | | Mapping-grade GNSS with RTK | RTK / NTRIP | 1–10 centimeters | | Survey-grade GNSS (Eos Arrow Gold, Trimble R12i) | RTK / NTRIP | 1–2 centimeters | *** Need help setting up your receiver with Felt? Contact our team at . --- # 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. 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