Instructions for Use
Ground Control Point (GCP) refers to control points located at specific positions and on particular targets within an image, possessing coordinate information in the mapping coordinate system. Due to their high-precision spatial coordinate data, GCPs are used in processes such as geometric correction of remote sensing imagery, positioning accuracy verification, and spatial registration to achieve high-precision georeferencing and positional tracking of image data.
SuperMap iDesktopX11i(2023) version starts to support this feature.
Parameter Description
Parameter Name | Parameter Interpretation | Parameter Type |
Dataset |
Displays the dataset containing the imagery used for generating ground control points. This field is not editable. |
DatasetMosaic |
Input Image Type | Select the type of imagery 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 based on specific circumstances. | ComboBoxImageType |
Error Threshold | The error threshold for outlier removal in image matching, with a range of [0,40]. The default is 5, and the unit is px. During image matching, the least squares method is used to fit the result points, removing points that exceed the error threshold. A larger threshold retains more tie points but increases the probability of preserving incorrect points. | Double |
Point Distribution Mode |
Select the ground control point distribution mode. Two options are provided: Conventional and Uniform. The default is Conventional.
|
PointDistributionMethod |
Density |
Available when Conventional is selected in Point Distribution Mode. Divides each overlapping area into N*M sub-regions and sets the intensity for generating ground control points: Sparse corresponds to 3*3 sub-regions; Medium corresponds to 4*4 sub-regions; Dense corresponds to 6*6 sub-regions. The default is Medium. Higher density requires longer computation and processing time. |
ImageMatchPointDensityLevel |
Matching Method |
Available when Conventional is selected in Point Distribution Mode. Five matching methods are provided: MOTIF, AFHORP, RIFT, SIFT, and DEEPFT. The default is MOTIF. Among these, AFHORP and RIFT support multi-modal data matching, while DEEPFT requires configuring an AI model and installing CUDA.
|
ImageMatchMethod |
Maximum Points per Block |
Available when Conventional is selected in Point Distribution Mode. The maximum number of points retained per image block during image matching. The range is [25,2048], and 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 tie point matching on each image. The 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 ensure sufficient matching 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.
|
SearchSeedPointMethod |
Template Size |
Available when Uniform is selected in Point Distribution Mode. Sets the interval size between seed points. The range is [1,256], and the default is 40, with the unit being px. A larger template size results in more reliable search points but requires more time. |
Integer |
Search Radius |
Available when Uniform is selected in Point Distribution Mode. Sets the search radius for seed points during image matching. The range is [0,256], and the default is 40, with the unit being px. A larger search radius increases the matching range but also requires more time. |
Double |
Semantic Culling of Non-Ground Points | Not selected by default. When selected, AI semantic technology is used to automatically remove ground control points in cloud areas and building areas. | Boolean |
Cloud Area |
Available after selecting Semantic Culling of Non-Ground Points. Selected by default. This means ground control points within cloud areas will be automatically removed based on the set dataset. If not selected, ground control points in cloud areas will be retained. |
Boolean |
Dataset |
Displayed after selecting Cloud Area and is not editable. For workflows related to DOM production, use the cloud amount data in Set Image Path. For workflows related to DSM production, use the cloud amount data in Set Image Path (DSM/DEM). |
DatasetVector |
Building Area | Available after selecting Semantic Culling of Non-Ground Points. Selected by default. This means building areas will be automatically identified, and ground control points in these areas will be removed. If not selected, ground control points in building areas will be retained. | Boolean |
Output Result
Generates a GroundControlPoint vector point dataset in the Control Point data source.
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