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How to import and mark Ground Control Points (GCPs) in PIX4Dcatch

Ground control points (GCPs) are reference points with known coordinates that ensure photogrammetry projects are accurately georeferenced and properly aligned. PIX4Dcatch supports capturing, importing, and marking GCPs.

IN THIS ARTICLE

Point Collection
Measure GCPs
Import GCPs to PIX4Dcatch
Mark GCPs in a PIX4Dcatch project
Processing projects with GCPs

Point Collection

A ground control point (GCP) is a point whose coordinates are known. Their coordinates have been measured with traditional surveying methods or have been obtained by other sources (LiDAR, older maps of the area, Web Map Service). GCPs are used to georeference a project. For more information about Point Collections, click here.

 

Measure GCPs

GCPs can be measured directly by PIX4Dcatch when paired with a supported RTK device or GPS.

Tip: Reference images and descriptive notes should be captured when measuring GCPs. This information makes it significantly easier to identify and mark the correct points in images during processing.Take reference images and add descriptions when measuring your GCPs. This detail will make it much easier to mark the correct points in the images later.

Import GCPs to PIX4Dcatch

PIX4Dcatch allows the import of existing GCPs and the creation or updating of a Point Collection.

Important: If importing to an existing collection, it must use the same coordinate reference system

 To import GCPs to an existing collection, follow the next steps:

  1. Go to the Survey tab.

    box survey

  2. Select the desired Point Collection.
    collection
  3. Tap Import Points.
    monument point 
  4. Select the file to import.
    gcp park

To import GCPs as a Point Collection, follow the next steps:

  1. Go to the Survey tab

    box survey

  2. Tap new Point Collection.
    collectionp
  3. Fill the name in Create the Point Collection and select Import Coordinate System.
    importar

  4. Tap Import file and select the file.
  5. Tap Create.
    createeee

Mark GCPs in a PIX4Dcatch project

To use GCPs in a project, the Point Collection must first be assigned to the project, after which the GCPs must be manually marked on the corresponding images. For more information, see: How to use automatic Tag Detection and manual GCP marking - PIX4Dcatch RTK

Processing project with GCPs

Once GCPs are marked on the images, the project can be processed to improve accuracy. For further details: Processing projects - PIX4Dcatch