Generate Ground Control Points
Feature Description
Ground Control Points (GCPs) are control points located at specific positions on imagery with coordinate information in the mapping coordinate system. Containing high-precision spatial coordinate data, they are used in processes like geometric correction of remote sensing imagery, positioning accuracy verification, and spatial registration to achieve high-precision georeferencing and positional tracking of image data.
Supported since SuperMap ImageX Pro 11i(2023) version.
Feature Entry
Imagery Tab->Geometric Correction Group->Generate Ground Control Points.
Parameter Description
- Input Image Type: Select the image type for GCP generation. Default: Panchromatic Image. Options include Multispectral Image, Forward-looking Image, Rear-view Image, or Front View and Rear View Image.
- Plane Accuracy: Determines whether preprocessing is needed during GCP matching.
- Low: Indicates image planar accuracy error exceeds 40 pixels, requiring preprocessing.
- High: Indicates image planar accuracy error below 15 pixels, no preprocessing needed.
- Medium: Auto-estimate accuracy when uncertain.
- Error Threshold: Set error threshold for outlier elimination in image matching. Range: [0,40], Default: 5 (px). Higher thresholds retain more points but increase error risks.
- Point Distribution Mode: Choose between Conventional and Uniform distribution.
- Conventional: Distributes points across overlap areas. Requires settings:
- Density: GCP density with Sparse, Medium, Dense options. Default: Medium.
- Matching Method: Choose from MOTIF, AFHORP, RIFT, SIFT, and DEEPFT. Default: MOTIF. AFHORP and RIFT support multimodal data.
- Block Max: Maximum points retained per block during matching. Range: [25,2048], Default: 256.
- Uniform: Evenly distributes points across overlap areas. Requires settings:
- Seed Point Count: Number of seed points per image. Range: [64,6400], Default: 512. Increase for low-texture images.
- Seed Point Search: Choose Grid Center or Corner Point method. Default: Corner Point.
- Corner Point: Selects distinctive points in region.
- Grid Center: Uses grid centers with randomness.
- Template Size: Interval between seed points. Range: [1,256], Default: 40 px. Larger sizes increase reliability and time.
- Search Radius: Matching search radius for seed points. Range: [0,256], Default: 40 px. Larger radii expand search scope and duration.
- Conventional: Distributes points across overlap areas. Requires settings:
- Semantic Culling of Non-ground Points: Uses AI to automatically remove control points in cloud and building areas.
- Cloud Area: Enabled when semantic culling is active. Default: checked (removes points in cloud areas).
- Building Area: Enabled when semantic culling is active. Default: checked (removes points in building areas).
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Figure: Automatically Generated Ground Control Points |
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