Connect PIX4Dcatch to the Pix4D-adapted viDoc RTK rover


The Pix4D-adapted viDoc RTK rover is a GNSS receiver which allows PIX4Dcatch to geolocate the images captured by your mobile device with centimeter accuracy. It is important to connect the device to the Pix4D-adapted viDoc RTK rover correctly to ensure accurate results.

This article explains how to connect the mobile device (phone or tablet) with the Pix4D-adapted viDoc RTK rover. The overall workflow consists of the following steps: Initialize Connection, Select Minimum Elevation, Select Constellations, Set Camera Offset Values, Enter NTRIP Credentials, Select Mountpoint and Select NTRIP CRS.

Initialize Connection

  1. Before you initialize the connection to the Pix4D-adapted viDoc RTK rover, please make sure that Bluetooth is activated from the mobile device settings.
  2. Turn on the Pix4D-adapted viDoc RTK rover with a single long press and wait until the green light appears.
  3. Start PIX4Dcatch. Pix4Dcatch_logo.jpg
  4. On the top-left corner of the screen, click on the GPS signal indicator and select Pix4D-adapted viDoc RTK via Bluetooth.


    Select Pix4D-adapted viDoc RTK via Bluetooth

  5. The RTK Device Settings dialog opens. Click on the device search bar and select your RTK device identifier.


    RTK Device Settings dialog for iPhone 13 Pro

Select Minimum Elevation

  1. Below the field where your RTK rover identifier is shown, click on the satellite bar (GPS, SBAS, GALILEO...). A new window will open and display the minimum elevation.
  2. The default minimum elevation value is 10°.
  3. The minimum elevation value ranges from 0° to 40° and increments by 5°.
  4. Tap on the right field (where the default value is displayed) and choose a different value from the dropdown list.



Select Minimum Elevation

Note: The more this value increases, the less satellites will be seen. In an empty area, it is recommended to keep the default value of 10°. 0° is not recommended due to greater atmospheric distortion from the horizontal satellites. 45° could end up with really few satellites visible.

Select Constellations

  1. In the Constellations section, the satellite navigation systems used for the geopositioning can be included or excluded.
  2. To include or exclude a satellite navigation system, toggle on/off the right button.
  3. The following constellations are available: GPS (cannot be deactivated due to hardware limitations), SBAS, GALILEO, QZSS, GLONASS, BEIDOU.


Select Constellations

Set Camera Offset Values

  1. When using the Pix4D-adapted viDoc RTK rover with a mobile device, the first step is to set the offset between the antenna and the mobile device camera (camera offset). 
  2. There are multiple combinations of mobile devices (phones and tablets) with the Pix4D-adapted viDoc RTK rovers where the camera offsets have been measured. These offsets are automatically recognized inside the app.
  3. If the mobile device has an unknown offset, it needs to be measured and filled out in the Camera Offset Values (X, Y, Z). If the X, Y, Z fields contain zero values, the app is unable to recognize the offset, and it has to be configured.
  4. The screenshot below shows all the possible camera offset options: SPC+, SPC and Custom.


Select Camera Offset Values

For more information: Camera offset - PIX4Dcatch RTK

NTRIP Credentials

  1. Enter the NTRIP details:
    • Hostname / IP (if IP is available, please use that as it is more reliable)
    • Port number
    • Username
    • Password
  2. Click on Validate NTRIP.


NTRIP Credentials

For more information: What is NTRIP?
Important: Please ensure that the device clock is synchronized. To synchronize the clock:
  • iPhone or iPad: go to Settings > General > Date & Time > toggle on Set Automatically
  • Android: go to Settings > General management > Date & Time > toggle on Automatic date and time
Tip: Download the viDoc Quickstart Checklist for on-site reference. The checklist includes the steps to connect to the Pix4D-adapted viDoc RTK and provides space to enter unique log-in details as well as general capture guidance for new users.

Other Languages: Pix4D-adapted viDocスタートガイド

Select Mountpoint

  1. After the NTRIP credentials have been validated, go to the Mountpoint section and select the preferred GNSS correction option.
  2. Depending on the CORS network, you can select a single base station or a triangulated network of the nearest base stations available.
Tip: Depending on the NTRIP service provider, there can be numerous mountpoint options to choose from. For more information about the available options, contact the NTRIP provider.


Select Mountpoints

Mountpoint Options

Mountpoint Options


Nearest | Net | VRS
  • Nearest: Single Base RTK corrections for the nearest reference station.
  • Net: Averages the position from the closest 3 base stations.
  • VRS: Averages the position from the closest 3 base stations and creates a virtual base somewhere on the site.
MSM Multiple Signal Messages - More messages sent with the RTCM 3.2 correction format.
RTCM Radio Technical Commission for Maritime Services - Open source correction format to send accurate position information.
  • RTCM 2.3: GPS Only
  • RTCM 3.2: GPS (including L5) + GLONASS + Galileo + BDS
CMR Compact Measurement Record - A Trimble-specific correction format. CMR and CMR+ are open to public use.
  • CMR: GPS Only
  • CMRx: compressed, GPS (including L5) + GLONASS + Galileo + BDS
iMAX Individualized Master Auxillary Correction - A Leica network that uses a real reference station as the source for the network corrections, so there is consistency and traceability for the corrections received by the rover.


  1. Go to the NTRIP Coordinate Reference System section.
  2. Select the coordinate reference system used by the NTRIP service to broadcast its correction.
  3. For more information about the CRS used, contact the NTRIP provider.
  4. The Connect button gets activated in blue after all the above-mentioned fields are shown with a green check box.
  5. Click on Connect.
  6. A successful connection to the NTRIP service is indicated with a green Pix4Dcatch_ViDoc_RTK_fix_green.jpg RTK icon.


Select CRS of the NTRIP Provider


The Pix4D-adapted viDoc is Ready to Connect


We compiled a list of coordinate reference systems commonly used for broadcasting NTRIP corrections from various regions. For more information, please check the table below.

Country or region Coordinate reference system
Europe ETRS 89 (EPSG: 4258)
United States NAD83(2011) (EPSG: 6318)
Japan JGD2011 (EPSG:6668)
Singapore SVY21 (EPSG:4757)

Next Steps

With the device properly connected to the Pix4D-adapted viDoc RTK rover, you are now ready to capture a project and measure points.To proceed, please go to Capture a project with PIX4Dcatch and Pix4D-adapted viDoc RTK rover.

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