If you prefer a stable wired connection instead of Bluetooth, you can connect your GNSS receiver to SurPad using USB (Serial Port mode). This method is especially useful for minimizing connection drops and ensuring consistent data flow.
What You’ll Need
Before you start, make sure you have the right hardware:
- An Android phone or tablet with USB OTG (USB Host) support
- A USB OTG cable (not just a charging cable)
- Your GNSS receiver
- A receiver with USB output (CDC/Serial) or a USB-to-UART / USB-to-RS232 adapter
- Optional: external power source or a powered OTG hub (if your phone can’t supply enough power)
Step 1: Connect the Receiver
Connect your GNSS receiver to your Android device using the USB OTG cable.
If your receiver requires more power than your phone can provide, use an external power source or a powered USB hub.
Once connected, make sure:
- The receiver is powered on
- The antenna is placed in an open-sky environment for optimal satellite visibility
Step 2: Configure SurPad
Open SurPad and navigate to:
Device → Communication
Set up the connection with the following parameters:
- Device Manufacturer: Other (or your specific receiver, if available)
- Device Type: RTK (NMEA0183)
- Communication Mode: Serial Port
From the list of available ports, select the USB serial port detected by your device.
Then set the correct baud rate (this depends on your receiver configuration).
Tap Connect to establish the connection.
Step 3: Check Data Flow
After connecting, verify that SurPad is receiving GNSS data:
- Open the satellite or position screen to confirm location updates
- Use the Debug menu to check incoming NMEA messages
For proper operation, your receiver should output at least:
- GGA
- RMC
For full data visibility and better diagnostics, it’s recommended to enable:
- GGA, RMC, VTG, GLL, GSA, GSV, GST
These messages provide detailed information about position, satellites, accuracy (DOP), and RMS values.
Step 4: Set Up NTRIP Corrections (Optional but Recommended)
To achieve centimeter-level accuracy, configure NTRIP corrections:
Go to:
Device → Rover
Then set:
- Data Link: Phone Internet
- Connect Mode: NTRIP
Enter your NTRIP credentials:
- IP / Host
- Port
- Mount point
- Username & Password
Apply the settings and return to the main screen.
Step 5: Confirm RTK Status
Open the Position Information screen and check the fix type:
- FLOAT – partial correction
- FIXED – full RTK accuracy
For best results:
- HDOP should be below 1
- HRMS / VRMS should indicate low error values
When everything is working correctly, you’ll get reliable centimeter-level positioning.
Final Notes
Using USB instead of Bluetooth gives you:
- More stable connection
- Lower latency
- Less risk of signal drop
However, make sure your hardware setup is properly powered — this is the most common issue with USB connections in the field.
