When you need to add/edit ground control points to improve accuracy, you can use the Manage Ground Control Points function.
For ease of management, the program uses two independent datasets to manage control points from different sources:
- Acquisition Control Point Dataset: Used to manage field-collected control points.
- Automatically Generated Control Points Dataset: Primarily used to store control points automatically generated through the Generate Ground Control Points function.
When opening the Manage Ground Control Points function, the Acquisition Control Point Dataset is managed by default. You can switch the dataset to be managed at any time via the Control Point Dataset drop-down menu in the management window.
For operations related to adding, modifying, and deleting points, please refer to Point Editing. The toolbar of the Manage Ground Control Points attribute table integrates multiple functions, including filtering, searching, sorting (ascending/descending), import field acquisition control point, export, delete, mass delete, and residual calculation. This article will focus on the filtering, import field acquisition control point, mass delete, and residual calculation functions.
This function is only available when the original image exists in the workflow.
SuperMap iDesktopX11i(2023) version starts to support.
Function Entry
Satellite Image Processing Tab->Geometric Correction Group->Generate Ground Control Points Drop-down Menu->Manage Ground Control Points.
Filter
Used to filter control points that meet the conditions in the attribute table, with the following three methods provided:
- Overview Map Range: The attribute table only displays tie point records shown in the overview map. When the overview map is closed, performing the filter operation will default display all tie points.
- Match Image: Check one or more images, and the attribute table will display control points associated with the specified images.
- SQL Expressions: Filter control points that meet the conditions based on the input expression.
Import Field Acquisition Control Point
In the remote sensing imagery production process, if the accuracy of the reference image is low and cannot meet project requirements, you can improve the accuracy of the result data by importing high-precision control points collected in the field. This method can effectively compensate for the shortcomings of the reference image, ensuring that the final results meet the required accuracy standards.
Main operational steps are as follows:
- In the Manage Ground Control Points window, click the Import Field Acquisition Control Point button on the toolbar, which will pop up the Collect Control Points dialog box.
- Set the following parameters in the dialog box:
- Control Point File: Select a *.txt, *.xls, or *.xlsx file stored locally that contains control point information. The first four columns of the control point file must be in the order of "Serial Number", "Longitude", "Latitude", and "Elevation"; otherwise, the import results may not match the actual information.
Figure: Control Point File - Source Coordinate System Settings: Set the coordinate system used when collecting control points to ensure that the longitude and latitude information of the control points remains highly accurate after coordinate system transformation to the default coordinate system of the acquisition control point dataset.
- X/Y Accuracy: The accuracy value of collect control points in the X/Y (longitude/latitude) direction, with a default value of 1 and unit of m. A smaller value means the control point has greater weight in adjustment.
- Z Precision: The accuracy value of collect control points in the Z (elevation) direction, with a default value of 1 and unit of m. A smaller value means the control point has greater weight in adjustment.
- List: After adding the control point file, the control point information in the file will be automatically read. You can use the checkboxes on the left side of the list to control whether to import the detected control points into the acquisition control point dataset. By default, all are checked, meaning all detected control points are imported.
- Control Point File: Select a *.txt, *.xls, or *.xlsx file stored locally that contains control point information. The first four columns of the control point file must be in the order of "Serial Number", "Longitude", "Latitude", and "Elevation"; otherwise, the import results may not match the actual information.
- Click the OK button to complete the control point import, and the Edit dialog box will automatically pop up.
- Select the first record in the Manage Ground Control Points window, and simultaneously choose the Edit button in the Edit dialog box to move the point's position to confirm the image coordinate of the control point in the original image.
- Repeat the operation in the fourth step to add image coordinates for all imported control points.
Mass Delete
Mass delete is used to delete all control points that meet the filter criteria. After clicking the mass delete button, the mass delete dialog box pops up, and the following content can be deleted:
- Delete Automatically Generated Control Points: When checked, all automatically generated control points will be deleted.
- Deletes The Points For The Specified Range Of Residuals: When checked, all control points with residuals greater than or equal to the value in the input box on the right will be deleted.
- Delete The Checkpoint: When checked, all checkpoints in the attribute table will be deleted.
Residual Calculation
Provides real-time residual and manual residual calculation, and the calculate result will be updated in real-time to the attribute table.
- Correction Model Type: Provides Linear RPC Correction Model, Quadratic Polynomial RPC Correction Model, and Cubic Polynomial RPC Correction Model, with Linear RPC Correction Model selected by default.
- Linear RPC Correction Model: Suitable for situations with small internal distortion in the image. This model requires at least 4 ground control points.
- Quadratic Polynomial RPC Correction Model: Suitable for situations with moderate internal distortion in the image. This model requires at least 9 ground control points.
- Cubic Polynomial RPC Correction Model: Suitable for situations with significant internal distortion in the image. This model requires at least 16 ground control points.
- Real-Time Residuals:
- Selected: Will real-time compute the residual information of each control point based on the correction model type. If the number of control points is less than required by the correction model, automatic real-time residual calculation will not be performed.
- Unselected (default option): Real-time residual calculation is not performed.
- Manual Residuals: Available when real-time residuals are not selected. Clicking this button will real-time compute the residual information of each control point based on the correction model type. If the number of control points is less than required by the correction model, residual calculation will not be performed.
Related Topics
Generate Ground Control Points