Setup Guide · SW Maps
SW Maps is a free GIS app for Android and iOS with a built-in NTRIP client. Once connected to a Bluetooth GNSS receiver, adding RTK corrections takes less than two minutes. This guide covers both platforms and the most common receiver types.
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Requirements
SW Maps is completely free
SW Maps has no paid tier, no ads and no feature restrictions. The built-in NTRIP client works with any correction service and any compatible GNSS receiver out of the box.
Turn on your GNSS receiver and pair it with your phone via the Android or iOS Bluetooth settings before opening SW Maps. Complete the Bluetooth pairing first — SW Maps discovers already-paired devices.
Open SW Maps and tap the antenna icon in the top bar (or open the left menu and select Bluetooth GNSS). You will see a list of paired Bluetooth devices.
Select your receiver from the list. If using USB OTG instead of Bluetooth, select USB Serial GNSS from the menu.
Set the Instrument Height to the distance from the ground to the bottom of your receiver (in metres). SW Maps applies the antenna offset automatically based on the receiver model if it is in the instrument list.
Tap Connect. SW Maps will begin streaming position data from your receiver. The status bar at the top will show satellite count and current fix type.
Go outside before connecting
Your receiver needs clear sky to acquire satellites. Connect to SW Maps indoors to test Bluetooth, but move outside with a clear sky view before opening the NTRIP client — corrections only work when the receiver has satellite lock.
Open the left navigation menu (tap the SW Maps icon top-left) and select NTRIP Client.
If NTRIP Client does not appear in the menu, your receiver is not yet connected — the NTRIP option only shows when SW Maps has an active instrument connection. Go back and connect your receiver first.
Fill in the following fields:
Tap the refresh icon next to the Mount Point field to load the sourcetable from the server. This downloads the list of available mountpoints so you can select the correct one for your location and device.
If your chosen mountpoint is a VRS (Virtual Reference Station) stream, enable Send NMEA GGA to NTRIP Caster. This sends your approximate position to the server so it can generate a local correction stream near you.
If you are using a standard (non-VRS) mountpoint, GGA is optional but does not cause problems if left enabled.
Tap Connect. If everything is correct, you will see the data stream counter begin incrementing — this confirms corrections are flowing from the server to your receiver. The NTRIP status button in the top bar turns green when connected.
Watch the position bubble on the SW Maps screen. It changes colour as your fix improves:
In a good environment with a nearby reference station, the bubble should turn green within 10–60 seconds of connecting to NTRIP. Once green, your position accuracy is at centimetre level.
To confirm, open the left menu and tap GNSS Status. You will see the fix type, estimated accuracy, number of satellites and PDOP. RTK Fixed with H accuracy below 0.03 m (3 cm) is a good result.
Green bubble = centimetre accuracy
Once SW Maps shows a green position bubble and your GNSS Status shows RTK Fixed, you are ready to collect or stake out points. Do not collect data while on Float — the accuracy is sub-metre, not centimetre.
For RTKsub, use these values in the SW Maps NTRIP client:
| Problem | Likely cause | Fix |
|---|---|---|
| NTRIP Client not in menu | No receiver connected | Connect a GNSS receiver first via Bluetooth GNSS or USB Serial GNSS. The NTRIP option only appears with an active instrument connection. |
| Cannot connect to server | No internet, wrong host, port blocked | Check mobile data is active. Verify host and port. Switch from Wi-Fi to mobile data if on a corporate network. |
| Sourcetable empty or fails to load | Wrong credentials or server unreachable | Verify username and password. Try copy-pasting from your account dashboard rather than typing. |
| Connected but bubble stays blue | Corrections not reaching receiver, or receiver indoors | Move outside. Check the data stream counter is incrementing. If it shows 0 bytes, GGA may be needed (enable it) or the mountpoint may be wrong. |
| Stuck on orange (Float) | Long baseline, obstructions, weak signal | Switch to VRS mountpoint. Move to open sky. Wait longer — Float can take several minutes in difficult conditions. |
| Green bubble but wrong coordinates | Datum mismatch in project settings | Check your SW Maps project coordinate system. SW Maps outputs WGS84 by default (EPSG:4326). For Netherlands: apply RD New transformation in your export settings. |
| Fix drops after a few minutes | Unstable internet connection | Use a dedicated mobile hotspot rather than tethering through another app. Enable auto-reconnect in SW Maps NTRIP settings if available. |
Saving NTRIP profiles
SW Maps supports multiple saved NTRIP profiles. After your first successful connection, your credentials are saved. You can add additional profiles for different services or mountpoints and switch between them from the NTRIP Client screen.