How to use PIX4Dcatch with viDoc RTK rover

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Using a viDoc RTK rover with PIX4Dcatch enables RTK centimeter grade absolute accuracies when capturing 3D scans and ground control points with a mobile device.

 
Basic requirements:
  • PIX4Dcatch app.
  • viDoc RTK rover.
  • NTRIP service subscription.
  • Internet access.
  • PIX4Dmapper, PIX4Dmatic, or PIX4Dcloud license for processing.

Install PIX4Dcatch

Connect PIX4Dcatch to the viDoc RTK rover

Before starting the image acquisition, charge the viDoc RTK rover for 6 hours.

  1. Mount the viDoc RTK rover to the mobile device.

 
Tip: To mount the viDoc RTK rover on the device.

Tablets:

  • Loosen the screw at the bottom of the rover.
  • Mount the rover onto the iPad/tablet, positioning it at the center.
  • The iPad has inbuilt magnets along its outer edges that ensure that the device is centered.
  • Once positioned, tighten the screw to the point at which the rover.
  • Measure the Camera Offset Value for Android devices.
Phones:
  • Insert the phone into the SP connect case.
  • Mount the rover to the case by following the instructions provided with the SP connect case.
  • Measure the Camera Offset Value for Android devices.
 
Important: When using an Android device, it will be necessary to measure the Camera Offset Values. For more information: How to measure the offset - PIX4Dcatch(Android) with viDoc RTK rover.

  2. Turn on the viDoc RTK rover with a single long press. The green light on the rover indicates it is turned on.

  3. Open the device settings and turn on Bluetooth if not already on.

  4. Start PIX4Dcatch. Pix4Dcatch logo

  5. Select the signal indicator in the top-left corner of the screen and select viDoc RTK via Bluetooth.

PIX4Dcatch viDoc RTK bluetooth dialog

Select viDoc RTK via Bluetooth.

  6. In the RTK Device Settings dialog:

PIX4Dcatch_RTK_device_settings_iOS_Android.jpg

RTK Device Settings dialog for iPhone(iOs) and Android.

  • When using an Android device, measure and enter the Camera Offset Values.

    For more information: How to measure the offset - PIX4Dcatch(Android) with viDoc RTK rover.

  • Select the viDoc RTK rover under Available Bluetooth Devices.
  • Enter the NTRIP details and tap Validate:
    • Hostname / IP
    • Port number
    • Username
    • Password

    For more information: What is NTRIP.

  • When the connection is established, select Choose mountpoint and select the preferred mountpoint.
  • Select the input coordinate system.
 
Important: Select the coordinate reference system used by the NTRIP service to broadcast its corrections as the Input Coordinate System. If uncertain, contact the NTRIP service provider for this information.

We have identified several input coordinate reference systems used for broadcasting NTRIP corrections from various regions. 

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

7. Tap Connect.

A successful connection to the NTRIP service is indicated with a green Pix4Dcatch ViDoc RTK fix icon RTK icon.

 
Note: Turn off the viDoc RTK rover after every use to avoid additional charges from the NTRIP service provider.
 
Important: Please ensure that the device clock is synchronized. To synchronize the clock:

iPhone or iPad:

  • Open the Settings app.
  • Tap General.
  • Tap Date & Time.
  • Verify that Set Automatically is toggled on.

Android:

  • Open the Settings app.
  • Tap General management.
  • Tap Date and time.
  • Verify that the Automatic date and time is toggled on.

Capture a dataset

Once the viDoc RTK rover is successfully connected to PIX4Dcatch, wait for RTK fixed. For an optimal experience, make sure the antenna is not obstructed and that you have a good internet connection.

 
Example: After RTK fixed is established, the Horizontal Accuracy and Vertical Accuracy are in the range of a few centimeters. In ideal conditions, the values are close to 0.01m/0.03ft.

PIX4Dcatch RTK fix information dialog

RTK dialog with optimal values.

Check the Status and the HDOP during the acquisition to ensure optimal conditions.

Status Explanation
No fix The data is not valid, there are not enough satellites visible, or there are internet connection problems.
Autonomous GNSS fix Only Differential GNSS is used for data measurements. DGNSS is an enhancement to GNSS, which determines its location based on a reference station, with no fixing of ambiguities. The accuracy of the determined position can be in the range of 10 m or more.
DGNSS Only The data is not valid, there are not enough satellites visible, or there are internet connection problems.
RTK Float The device does not have enough satellites in common with the base station (i.e., Mount Point), or the reflected signals of satellites are received. The accuracy of the determined position can be in the range of 1 m.
RTK Fixed The GNSS rover and base station (i.e., Mount Point) can see at least five satellites in common, and the rover is receiving corrections from the base station. The accuracy of the determined position can be in the range of a few centimeters.
HDOP

HDOP (Horizontal Dilution of Precision) indicates how good the position and distribution of the satellites are.

Generally, the HDOP value is considered ideal below 1, and to have centimeter-level accuracy, from some testing, it has been observed that for better accuracy, we should take the readings which have a value lower than 0.65.

The accuracy values can vary and depend on multiple factors, for example:

  • Blocked and reflected GNSS signal, close to buildings, trees, or bridges.
  • Rapid movements of the device.
  • Poor cellular reception.

For more information: GNSS and viDoc RTK rover best practices.

For more information: Capturing a dataset - PIX4Dcatch.

Process the dataset

With a captured PIX4Dcatch project, there are several options for processing a 3D model. Directly upload and process to PIX4Dcloud / PIX4Dcloud Advanced for the most immediate results, or export the project and process using PIX4Dmatic or PIX4Dmapper.

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