How to use coordinate reference systems in PIX4Dcatch

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A coordinate reference system provides information and parameters that ensure coordinates are correctly displayed on a map. Depending on your configuration, you will need to select the appropriate input and output coordinate reference systems and the geoid when applicable. 

 
Tip: When discussing coordinate reference systems, it is highly recommended to use EPSG codes. The coordinate reference system can easily and unambiguously identify with an EPSG code. Using only the names can be confusing, and they can often be misinterpreted. Check the http://epsg.org/ website to search for the desired coordinate reference system.

Refer to Coordinate reference systems and 2D projections for more information.

Input coordinate reference system

When using an RTK-enabled device, the input coordinate reference system is determined by what is selected when connecting to the NTRIP service.

 
Note: For non-RTK captures, PIX4Dcatch automatically sets the horizontal coordinate reference system to WGS84 (EPSG:4326) and the vertical coordinate reference system to EGM96 height (EPSG:5773).

Select the input coordinate reference system using the viDoc RTK rover

  • Tap the signal indicatorarrow down iconthen select ViDoc RTK via Bluetooth.

    PIX4Dcatch viDoc RTK bluetooth dialog

    Select ViDoc RTK via Bluetooth.

  • In the RTK Device Settings dialog:

    PIX4Dcatch RTK device settings dialog

    RTK Device Settings dialog window.

  • Select the viDoc RTK rover under Available Bluetooth Devices.
  • Enter the NTRIP details, then tap Connect:
    • Hostname / IP
    • Port Number
    • Username
    • Password
  • When the connection is established, under Choose mountpoint, select the preferred mountpoint.
  • Tap coordinate reference system icon to 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)
  • Tap Save.

Output coordinate reference system

The output coordinate reference system is used to reference the reconstruction after processing. It does not need to be the same as the input coordinate reference system or the GCPs coordinate reference system.

 
Note: When uploading a project to PIX4Dcloud/PIX4Dcloud Advanced with RTK image geolocation, it is possible to manually select the horizontal and vertical coordinate reference systems and the geoid (when available). It is also possible to select the output coordinate system when an exported project is imported into PIX4Dmatic, PIX4Dmapper, or another third-party software.
Refer to How to Use Coordinate Systems to select the CRSs in PIX4Dmatic
Refer to Select Output Coordinate System to select the output CRS in PIX4Dmapper

Select the output coordinate reference system when uploading to PIX4Dcloud / PIX4Dcloud Advanced (RTK enabled device)

1. Tap Upload upload button

PIX4Dcatch trench captured project view

Captured project ready for upload.

2. Tap coordinate reference system icon Output coordinate system.

PIX4Dcatch select output coordinate reference system dialog RTK

The Upload Project dialog. Auto Detected is the default setting.

3. Tap Manual to select the horizontal and vertical coordinate reference system.

 
Note: Auto Detected sets the horizontal coordinate reference system in the UTM zone corresponding to the location of the project. e.g. the horizontal coordinate reference system to WGS84 / UTM zone 32N (EPSG:32632) and the vertical coordinate reference system to EGM96 height (EPSG:5773), for Lausanne, Switzerland.

PIX4Dcatch select output coordinate reference system on Upload

The Manual selection dialog. Choose the output coordinate reference system when uploading the project.

To manually select the output coordinate reference system:

  • Tap projected coordinate reference system icon to select the horizontal coordinate reference system:
    • In the Horizontal coordinate reference system dialog, search or copy-paste:
      • The name
        or
      • The EPSG code of the coordinate system.
  • Tap altitude icon to select the vertical coordinate reference system:
    • In the Vertical coordinate reference system dialog, search or copy-paste:
      • The name
        or
      • The EPSG code of the coordinate system.
  • (Optional) Tap globe icon to select a geoid: If the selected vertical coordinate system supports geoids and the geoid model is available in the PIX4D database, select the geoid model in the drop-down list.
  • Tap Done.
     
    Important: Ensure the correct vertical coordinate system and/or geoid is selected.
  • Tap Upload.

Refer to How to use vertical coordinate systems and geoids - PIX4Dmatic for more detailed information, plus a current list of available geoids is available in the FAQ.

 
Note: For non-RTK captures, PIX4Dcatch automatically sets the output coordinate reference system in the autodetected UTM zone corresponding to the location of the project, e.g. the horizontal coordinate reference system to WGS84 / UTM zone 32N (EPSG:32632) and the vertical coordinate reference system to EGM96 height (EPSG:5773), for Lausanne, Switzerland.

GCPs coordinate reference system information

When collecting GCPs it is possible to select the coordinate reference system to export the GCPs in.

PIX4Dcatch new GCP coordinate reference system collection RTK

New GCP collection dialog.

Note: When creating a new GCP collection PIX4Dcatch will prefill the horizontal and vertical fields depending on the current region and configuration information.
  • With viDoc RTK rover:
    • Horizontal: Depends on the NTRIP CRS entered. e.g. ETRS89 (EPSG:4258), NAD83(2011) (EPSG:6318), JGD2011 (EPSG:6668), etc.
    • Vertical: Ellipsoidal height
  • With GPS:
    • Horizontal: WGS 84 (EPSG:4326)
    • Vertical: EGM 96
 
Important: The same coordinate reference system used to collect GCPs must be selected when importing the GCP files into PIX4Dmatic, PIX4Dmapper, or any other third-party software.

Refer to How to import GCPs to PIX4Dmatic, or How to add / import GCPs in the GCP/MTP Manager (PIX4Dmapper) for more information.

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