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Calibrate
Access:
- Click Process
. - On the Menu bar, click Process > Calibrate.
It allows users to change the following processing options:
- Image scale: Defines the image size used to extract keypoints.
- Keypoints: Sets up the number of extracted keypoints.
- Reoptimize cameras: Fast reprocess the project after applying changes to Ground Control Points (GCPs).
Image scale
Defines the image size at which keypoints are extracted in comparison to the initial size of images. It is possible to select:
- 1 (Original image size): This is the recommended Image scale.
- 1/2 (Half image size): A scale of 1/2 (half image size) can be used to speed up processing and for cameras with very high resolution.
- 1/4 (Quarter image size): To get a fast overview and to assess the completeness of the project, a scale of 1/4 (quarter image size) can be used to speed up processing.
- 1/8 (Eighth image size): To get a fast overview and to assess the completeness of the project, a scale of 1/8 (eighth image size) can be used to speed up processing.
Tip: Reducing the Image scale will, usually, result in a slightly reduced accuracy because fewer features will be extracted. On the other hand, it can help to calibrate datasets with blurry images or datasets containing homogenous areas. We recommend reducing the Image scale:
- To speed up processing.
- To get a fast overview and to assess the completeness of the project.
- For datasets containing blurry images.
- When processing datasets of flat and homogenous or repetitive and complex areas (trees, forest, fields) as it can result in a higher number of calibrated images.
Information: The keypoints are computed on multiple image scales, starting from the selected value and going to the 1/8 scale. For example, if 1/2 (half image size) is selected, the keypoints are computed on images with half, quarter, and eighth image size.
Keypoints
Allows to set up the number of extracted keypoints.
- Auto (Default): Automatic way to select which keypoints are extracted.
- Custom: Directs Pix4Dmatic to identify a specific number of keypoints, image content permitting.
- Number of Keypoints: Maximum number of keypoints to be extracted per image.
Information: When extracting keypoints per image, an internal scoring is assigned to them. Based on this scoring the best keypoints are selected.
Reoptimize cameras
This process is used to reoptimize already computed internal and external camera parameters. It can be used when changes to GCPs are applied after the Calibrate step is completed.
Tip: Using the Reoptimize cameras option reduces the processing time after applying changes to GCPs.
Such changes can be:
- Adding GCPs marks.
- Changing the position of existing GCPs marks.
- Removing GCPs with marks.
Important: The project is reoptimized only when all other Calibrate options remain unchanged. For example, when changing the Image scale or Keypoints, the whole Calibrate step is re-run.
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