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.
- PIX4Dcatch app.
- viDoc RTK rover.
- NTRIP service subscription.
- Internet access.
- PIX4Dmapper, PIX4Dmatic, or PIX4Dcloud license for processing.
IN THIS ARTICLE
Install PIX4Dcatch
Connect PIX4Dcatch to the viDoc RTK rover
Capture a dataset
Process the dataset
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.
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.
- 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.
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. 
5. Select the signal indicator in the top-left corner of the screen and select viDoc RTK via Bluetooth.
Select viDoc RTK via Bluetooth.
6. In the RTK Device Settings dialog:
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.
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 
RTK icon.
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.
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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