Camera offset - PIX4Dcatch RTK

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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). This offset allows PIX4Dcatch to accurately compute the locations recorded by the Pix4D-adapted viDoc RTK rover for the content captured (scans or GCPs) and obtain precise measurements. Currently, the camera offset can be measured automatically by Pix4Dcatch (SPC and SPC+) or manually by the user.

Which Version of Pix4D-adapted viDoc RTK Rover do I have?

Currently, the Pix4D-adapted viDoc RTK rover has different versions that require different offset values: viDoc compatible with SPC+ connector (Pix4D-adapted viDoc RTK rover P01) and viDoc compatible with SPC connector. This section describes how to identify the Pix4D-adapted viDoc RTK rover version, in order to set the correct camera offset values and achieve the best available accuracy of the reconstruction.

 
Important: The list of compatible iOS mobile devices with SPC/SPC+ connectors and Pix4D-adapted viDoc models is available here.

Smartphone type with SPC+ connector

Since SP Connect released a new version of their adapter called SPC+, Pix4D released Pix4D-adapted viDoc RTK rover P01, a new version of the Pix4D-adapted viDoc RTK rover that is now compatible with the new SPC+ cases. This device version is indicated by the additional Pix4D logo and the rounded shape of the new SPC+ mount type. Manual offset measurement is only needed in the following situations:

  • PIX4Dcatch does not recognise the device
  • A custom case is used
 
Important: The list of compatible iOS mobile devices with SPC/SPC+ connectors and Pix4D-adapted viDoc models is available here.


To get the list of known devices, please refer to the section Devices with known offset.

P01 label extension

P01_upgrade_by_pix4d.png

Connector on Pix4D-adapted viDoc RTK rover

Connector on the SPC+ case

Smartphone type with SPC connector

This Pix4D-adapted viDoc RTK rover version is compatible with the old SPC cases and can be recognized easily by the rectangular mount type and the black label without the Pix4D logo. Manual offset measurement is only needed in the following situations:

  • PIX4Dcatch does not recognise the device
  • SPC universal case is used
  • A custom case is used
 
Important: The list of compatible iOS mobile devices with SPC/SPC+ connectors and Pix4D-adapted viDoc models is available here.


To get the list of known devices, please refer to the section Devices with known offset.

Connector on Pix4D-adapted viDoc RTK rover
Connector on the SPC case

Tablet type

This type of Pix4D-adapted viDoc RTK rover is not available anymore and it was used with iPads. All device combinations are with a known offset, so no manual offset measurement is needed.
viDoc_old.png

Devices with a Known Camera Offset

This list contains the combinations of mobile devices (phones and tablets) with the Pix4D-adapted viDoc RTK rovers where the camera offsets are already measured. PIX4Dcatch will automatically fill in the X, Y, Z fields with the correct camera offset values.

Smartphone model  Compatibility with the case type
[iPhone] SPC SPC+
iPhone 15 Pro Max
iPhone 15 Pro
iPhone 14 Pro Max ✅*
iPhone 14 Pro ✅*
iPhone 13 Pro Max
iPhone 13 Pro
iPhone 12 Pro Max
iPhone 12 Pro
iPhone 11 Pro Max
iPhone 11 Pro
iPhone XR
 
* Warning: This configuration is not recommended due to partial camera sensor occlusion.
Tablet model Compatibility with the case type
[iPad] SPC SPC+
iPad Pro 12.9-inch (4th, 5th and 6th generation)
iPad Pro 11-inch (2nd, 3rd and 4th generation)
 
Important: If the Pix4D-adapted viDoc RTK rover is not mounted with an SP-connect case, then offset values need to be measured manually, as described below. In PIX4Dcatch, there is an option to overwrite the autodetected values with the manually measured ones.

Camera Offset Measurements

When initiating the connection to the Pix4D-adapted viDoc RTK rover, the dialog RTK Device Settings opens. The section Camera Offset allows the user to set the X, Y, Z offset values properly. The available options depend on the combination of the Pix4D-adapted viDoc RTK device version, the mobile device and the device case. The following options are available: SPC, SPC+ (in tablet and older mobile app versions: Automatic) and Custom.

The options SPC and SPC+ are only available if the combinations of the Pix4D-adapted viDoc RTK device version, the mobile device and the device case are known. The option Custom is always available and intended to be used by universal or specific cases. This option requires measuring the camera offsets manually and setting them in PIX4Dcatch. The camera offset value selection is saved for the next measurements and modifications are only needed if the setup changes.

Camera_Offset_Options.png

Camera offset options (iPhone 13 Pro example): SPC+, SPC and Custom.

How to Manually Measure the Camera Offset

PIX4Dcatch_RTK__measure_z_offset_IPHONE_.jpgPIX4Dcatch_RTK__measure_z_offset_IPAD_.jpg

Mounted device illustrating the orientation of axes to measure.

Mount the device to the Pix4D-adapted viDoc RTK rover using the appropriate SP-connect case. Phone cases can be purchased separately from the SP-connect website. The SP-connect universal phone mount can be used if the specific model is unavailable. SP-connect cases are also available in most bicycle and motorcycle shops.

Place the device in landscape mode and the display to the front. Notate the orientation of the X, Y, and Z axes and how they relate to the point of origin on the antenna to measure from. The point of origin resides in the middle of the screw mount at the base of the antenna. It will also be necessary to determine which lens to measure from for devices with multiple camera lenses.

For more information: Mounting a device to the Pix4D-adapted viDoc RTK rover.

 
Important: If you use iPad, make sure the device is in landscape mode and the antenna is pointing upwards, like in the image above. The X and Y offset values will need to be entered as negative values.
 
Tip: If you don't know which camera lens to measure from, start PIX4Dcatch and then place something in front of each camera lens. The lens blocked is the appropriate lens to measure from.
 
Important: When using the universal mount, the lens and device must be below the antenna when mounting the device to the Pix4D-adapted viDoc.

 PIX4Dcatch_Android_RTK_x_Not_Above_origin.jpg      PIX4Dcatch_Android_RTK_check_Not_Above_origin.jpg

Measure the X axis (Y axis for iPad)

Measure the value from the antenna base to the center of the lens along the axis for the X axis offset.

PIX4Dcatch Android RTK measure x offset diagram

How to measure the X axis.

Measure the Y axis (X axis for iPad)

Measure the value from the center of the antenna to the center of the lens along the axis for the Y axis offset.

PIX4Dcatch Android RTK measure y offset diagram

How to measure the Y axis.

Measure the Z axis

Measure the depth from the center of the antenna to the center of the lens for the Z axis offset.

PIX4Dcatch Android RTK measure z offset diagram

How to measure the Z axis.

 
Important: Most cases and adaptors are adding extra offset on top of the screen. Make sure that Z axis offset is measured to the lens and not the case/adaptor.

Enter the camera offset values

With the camera offsets properly measured and recorded, they can be included in the appropriate Camera Offset Values field of the RTK Device Settings dialog. Depending on the device's geographical region, centimeters or inches will be the displayed measurement unit.

PIX4Dcatch_RTK_offset_type_custom.png

PIX4Dcatch_RTK_offset_type_custom_enter.png

RTK Device Settings dialog for iOS.

 
Important: Ensure that camera offset values are defined in the correct measurement units. For Android phones, setting the unit is not directly available and it is tightened to the language settings. It can be adjusted in the Android global settings under Languages (or App languages). For iOS, setting the unit is available under the General settings -> Language & Region -> Measurement system.

The camera offset is now properly set in the Camera Offset Values X, Y, Z fields. Continue with the RTK Device Settings dialog to complete the Pix4D-adapted viDoc RTK connection to the device.

For more information: How to use Pix4Dcatch with Pix4D-adapted viDoc RTK rover.

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