Generate Ground Control Points

Feature Description

A ground control point (GCP) is a control point located at a specific position and on a specific target in an image, with coordinate information in the mapping coordinate system. Due to its high-precision spatial coordinate data, it can be used in processes such as remote sensing imagery geometric correction, positioning accuracy verification, and spatial registration to achieve high-precision geographic referencing and positional tracking of image data.

SuperMap iDesktopX11i(2023) starts to support this feature.

Parameter Description

Parameter Name Parameter Interpretation Parameter Type
Dataset

Displays the dataset containing the image used for generating ground control points. It is not editable.

DatasetMosaic
Input Image Type Selects the type of image used for generating ground control points. The default is Panchromatic Image. It can also be switched to Multispectral Image, Forward-looking Image, Rear-view Image, or Front View and Rear View Image according to specific circumstances. ComboBoxImageType
Error Threshold The error threshold for gross error elimination in image matching. The value range is [0,40]. The default is 5, and the unit is px. During the image matching process, the least squares method is used to fit the result points, and points exceeding the error threshold are removed. A larger threshold preserves more tie points but increases the probability of retaining incorrect points. Double
Point Distribution Mode

Selects the ground control point distribution mode. Two methods are provided: Conventional and Uniform. The default is Conventional.

  • Conventional: Divides each scene into N*M sub-regions, and then selects n image blocks of size 512*512 from each sub-region for control point generation. The generated ground control points will try to cover the entire image as much as possible.
  • Uniform: The generated ground control points will be evenly distributed across each scene image. The number of points is fewer than that of regular distribution, but the distribution is more uniform, which is suitable for situations where the internal distortion of the image is significant.
PointDistributionMethod
Number of Blocks in Column Direction

Available after selecting Conventional in Point Distribution Mode.

The number of blocks into which each scene image is divided in the column direction. The default value is 4.

Integer
Number of Blocks in Row Direction

Available after selecting Conventional in Point Distribution Mode.

The number of blocks into which each scene image is divided in the row direction. The default value is 4.

Integer
Matching Method

Available after selecting Conventional in Point Distribution Mode.

Provides the following six matching methods to choose from based on data characteristics and requirements. Among them, the AFHORP and RIFT methods support multi-modal data matching; CASP and DEEPFT are based on deep learning and require additional AI model configuration and CUDA environment installation. Generally, MOTIF, CASP, or DEEPFT are recommended.

  • MOTIF (Default): A template matching algorithm for multimodal imagery, characterized by its lightweight feature descriptors. MOTIF can overcome nonlinear radiometric distortions caused by differences between SAR and optical images.
  • CASP: A novel cascade matching pipeline that benefits from integrating high-level features, helping to reduce the computational cost of low-level feature extraction. This pipeline decomposes the matching stage into two progressive phases. It first establishes one-to-many correspondences at a coarser scale as cascade priors. Then, leveraging these priors for guidance, it determines one-to-one matches at the target scale.[1]
  • DEEPFT: A deep learning-based image matching method.
  • SIFT: A method for extracting distinctive invariant features from images, which can be used for reliable matching between objects or scenes under different viewpoints.
  • RIFT: A feature matching algorithm robust to large-scale nonlinear radiometric distortions. It enhances the stability of feature detection and overcomes the limitations of feature description based on gradient information.
  • AFHORP: A feature matching algorithm for multimodal imagery. AFHORP exhibits strong resistance to radiometric distortions and contrast differences in multimodal images, performing excellently in addressing issues of direction reversal and abrupt phase extremum changes.
ImageMatchMethod
Maximum Points per Block

Available after selecting Conventional in Point Distribution Mode.

The maximum number of points retained within each image block during image matching. The value range is [1,2048], and the default is 256.

Integer
Number of Seed Points

Available after selecting Uniform in Point Distribution Mode.

Sets the number of seed points for conjugate point matching on each scene image. The value range is [64,6400], and the default is 512. When the image texture is poor, it is recommended to increase the number of ground control points to match enough points and improve subsequent imagery quality.

Integer
Seed Point Search Method

Available after selecting Uniform in Point Distribution Mode.

Sets the method for searching seed points. The default is Raster Center Point.

  • Corner Point: Uses points with distinct features within the selected region as seed points.
  • Raster Center Point: Uses the center point of the raster as the seed point. This search method is random.
SearchSeedPointMethod
Template Size

Available after selecting Uniform in Point Distribution Mode.

Sets the interval size between seed points. The value range is [1,256], the default is 40, and the unit is px. A larger template leads to more reliable searched points but longer processing time.

Integer
Search Radius

Available after selecting Uniform in Point Distribution Mode.

Sets the search radius for seed points in image matching. The value range is [0,256], the default is 40, and the unit is px. A larger search radius increases the matching range but also increases the processing time.

Double
Semantic Culling of Non-Ground Points Not checked by default. When checked, ground control points within cloud areas and building areas can be automatically culled based on AI semantic technology. Boolean
Cloud Area

Available after Semantic Culling of Non-Ground Points is checked.

Checked by default, meaning ground control points within cloud areas will be automatically culled based on the set dataset. If unchecked, ground control points in cloud areas will be retained. The dataset must contain an ImageName field, and the name must correspond to the image currently to be processed.

Boolean
Dataset

Displayed after "Cloud Area" is checked. Not editable.

For workflows related to DOM production, use the cloud amount data from Set the Image Path.

For workflows related to DSM production, use the cloud amount data from Set Image Path (dsm/dem).

DatasetVector
Building Area Available after Semantic Culling of Non-Ground Points is checked. Checked by default, meaning building areas will be automatically identified and ground control points within these areas will be culled. If unchecked, ground control points in building areas will be retained. Boolean

Output Result

Generates a GroundControlPoint vector point dataset in the Control Point datasource.

Related Topics

Set the Image Path

Set Image Path (dsm/dem)

Generate Connection Points

Block Network Adjustment

References

[1] Chen, P., Yu, L., Wan, Y., Pei, Y., Liu, X., Yao, Y., ... & Zhang, Y. (2025). CasP: Improving Semi-Dense Feature Matching Pipeline Leveraging Cascaded Correspondence Priors for Guidance. In Proceedings of the IEEE/CVF International Conference on Computer Vision (pp. 28063-28072).