Processing steps

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This section describes the three steps for processing with Pix4Dag.

1. Initial processing

In this step the images and additional inputs such as GCPs described in section Inputs and Outputs will be used to do the following tasks:

  • Keypoints extraction: Identify specific features as keypoints in the images.
  • Keypoints matching: Find which images have the same keypoints and match them.
  • Camera model optimization: Calibrate the internal (focal length,...) and external parameters (orientation,...) of the camera.
  • Geolocation GPS/GCP: Locate the model if geolocation information is provided.

Automatic Tie Points are created during this step. These are the basis for the next steps of processing.

For more information about outputs, see section Inputs and Outputs.

2. Point cloud and mesh

This step will build on the Automatic Tie Points with:

  • Point Densification: Additional Tie Points are created based on the Automatic Tie Points that results in a Densified Point Cloud.
  • 3D Textured Mesh: Based on the Densified Point Cloud a 3D Textured Mesh can be created.

3. DSM, orthomosaic and index

This step enables the creation of:

  • Digital Surface Model (DSM): The creation of the DSM will enable the computation of Volumes, Orthomosaics and Reflectance Maps.
  • Orthomosaic: The creation of the Orthomosaic is based on orthorectification. This method removes the perspective distortions from the images.
  • Reflectance Map: The goal is to produce a map where the value of each pixel faithfully indicates the reflectance of the object.
  • Index Map: Generate an Index Map where the color of each pixel is computed using a formula that combines different bands of the Reflectance Map(s).

 

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