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.
  • 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).
Figure: Automatically Generated Ground Control Points

Related Topics

Generate Tie Points

Manage Tie Points

Manage Ground Control Points

Block Adjustment