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, along with the geoid when applicable. 

 
Tip: When discussing coordinate reference systems, it is highly recommended to use EPSG codes. The coordinate reference system can be easily and unambiguously identified 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 setting up the NTRIP service. 

For non-RTK captures, PIX4Dcatch automatically sets the horizontal and vertical input coordinate reference system to WGS84 (EGM 96). 

Select the input coordinate reference system using the viDoc RTK rover

  • Tap the signal indicatorarrow_down.svgthen select ViDoc RTK via Bluetooth.

    viDoc RTK via Bluetooth

    Select ViDoc RTK via Bluetooth.

  • In the RTK Device Settings dialog:

    RTK_device_settings_NTRIP.png

    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 system icon to select the input coordinate system.
 
Note: The input coordinate system is determined by the NTRIP service provider and is usually in the system that's local to the country. For example, we have identified that for most European countries, it is ETRS 89 (EPSG 4258) and across the US it is NAD83 (EPSG 4269).
  • Tap Save.

Output coordinate reference system

The output coordinate reference system is used to reference the reconstruction after processing and 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, along with 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 the cloud (RTK enabled device)

  • Tap Upload upload.png

    PIX4Dcatch main project screen

    Captured project ready for upload.

  • Tap PIX4Dcatch coordinate system icon Output coordinate system.

    Upload_dialog_RTK.png

    Upload Project dialog.

  • Use the Auto Detected, or tap Manual to select the horizontal and vertical coordinate reference system.
     
    Note: Auto Detected sets the output coordinate reference system in the autodetected UTM zone corresponding to the location of the project, e.g. WGS 84 / UTM zone 32N (EGM 96 Geoid) for Lausanne, Switzerland.

    Choose the output coordinate system dialog window

    Manual selection dialog to choose the output coordinate reference system when uploading the project.

To manually select the output coordinate reference system:

  • Tap PIX4Dcatch projected Coordinate 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 PIX4Dcatch 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 Geoid 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.

 
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. WGS 84 / UTM zone 32N (EGM 96 Geoid) for Lausanne, Switzerland.

GCPs coordinate reference system information

When collecting GCPs using PIX4Dcatch the GCP coordinate reference system is EPSG: 4326 WGS84 by default. When using the viDoc RTK rover the GCP coordinate reference system is determined by the NTRIP service.

 
Note: The GCPs coordinate reference system is referenced in the Project_name_complete.csv file.

GCP Complete.csv file

Complete.csv file including the Input Coordinate System.

Refer to How to export GCPs to see how to export this file.
 
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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