Generate Connection Points

Feature Description

Connection points are homologous image points that can construct 3D models or establish connection relationships between adjacent models (images). Generating connection points helps improve accuracy during geometric correction, ensuring the spatial consistency of the imagery.

SuperMap iDesktopX supports this feature starting from version 11i(2023).

Parameter Description

Parameter Name Parameter Interpretation Parameter Type
Dataset

Displays the dataset containing the imagery used for generating connection points. It is not editable.

DatasetMosaic
Input Image Type Select the type of imagery used for generating connection 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 based on the specific situation. ComboBoxImageType
Refer to the Adjustment File

Based on existing adjustment file information, make the newly generated connection points approximate the accuracy of the existing ones. Use the Add and Delete buttons in the toolbar to conveniently manage multiple reference adjustment files.

The reference adjustment file is obtained from the Block Network Adjustment function.

ReferenceFileData
Error Threshold

The error threshold for gross error elimination during 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, removing points greater than the error threshold. A larger threshold retains more connection points but increases the probability of retaining erroneous points.

Double
Point Distribution Mode

Select the connection point distribution mode. Two methods are provided: Conventional and Uniform. The default is Conventional.

  • Conventional: Divides each overlapping area into N*M sub-regions, then selects n 512*512 image blocks from each sub-region for homologous point matching, ensuring the stability and reliability of the homologous points. The generated connection points will cover the entire overlapping area as much as possible.
  • Uniform: The generated connection points will be evenly distributed within the overlapping area. The number of points is less than in the conventional distribution, but the distribution is more uniform. This is suitable for situations where the internal distortion of the imagery is significant.
PointDistributionMethod
Number of Blocks in Column Direction

Available when Conventional is selected in Point Distribution Mode.

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

Integer
Number of Blocks in Row Direction

Available when Conventional is selected in Point Distribution Mode.

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

Integer
Matching Method

Available when Conventional is selected in Point Distribution Mode.

Six matching methods are provided, and one can be selected based on data characteristics and requirements. Among them, the AFHORP and RIFT methods support multimodal data matching; CASP and DEEPFT are based on deep learning and require additional configuration of AI models and installation of the CUDA environment. In general, it is recommended to use MOTIF, CASP, or DEEPFT.

  • MOTIF (default): A template matching algorithm for multimodal imagery, characterized by the use of lightweight feature descriptors. MOTIF can overcome nonlinear radiometric distortion caused by differences between SAR and optical images.
  • CASP: A novel cascaded matching pipeline that benefits from integrating high-level features, helping to reduce the computational cost of low-level feature extraction. The pipeline decomposes the matching phase into two progressive stages, first establishing one-to-many correspondences at a coarser scale as cascaded priors. Then, using these priors for guidance, one-to-one matches are determined at the target scale.[1]
  • DEEPFT: An image matching method based on deep learning.
  • SIFT: A method for extracting distinctive invariant features from images, which can be used for reliable matching between objects or scenes under different viewing angles.
  • RIFT: A feature matching algorithm robust to large-scale nonlinear radiometric distortion. It can improve the stability of feature detection and overcome the limitations of feature description based on gradient information.
  • AFHORP: A feature matching algorithm for multimodal imagery. AFHORP has strong resistance to radiometric distortion and contrast differences in multimodal imagery and performs excellently in solving problems of orientation reversal and phase extremum mutation.
ImageMatchMethod
Maximum Per Block

Available when Conventional is selected in Point Distribution Mode.

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

Integer
Number of Seed Points

Available when Uniform is selected in Point Distribution Mode.

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

Integer
Seed Point Search

Available when Uniform is selected in Point Distribution Mode.

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

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

Available when Uniform is selected 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 makes the searched points more reliable but takes longer.

Integer
Search Radius

Available when Uniform is selected in Point Distribution Mode.

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

Double
Semantic Culling of Non-ground Points Not selected by default. When selected, connection points within cloud areas and building areas can be automatically culled based on AI semantic technology. Boolean
Cloud Area Available after selecting Semantic Culling of Non-ground Points. Selected by default, meaning connection points within cloud areas will be automatically culled based on the set dataset. If not selected, connection points within cloud areas will be retainedThe 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 selected. It is 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 selecting Semantic Culling of Non-ground Points.

Selected by default, meaning building areas will be automatically identified and connection points within those areas will be culled. If not selected, connection points within building areas will be retained.

Boolean

Output Result

A TiePoint vector point dataset is generated in the Control Point datasource.

Related Topics

Set the Image Path

Set Image Path (dsm/dem)

Generate Ground Control 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).