# Edit Control Points If the product generated by only inputting the photo positioning data does not meet the absolute accuracy requirement, control points should be added after the relative orientation to achieve absolute orientation and improve the absolute accuracy of the product. ## Working Interface Click **Edit GCP** to open the control point editing interface, as shown in the figure below:

The interface is divided into four parts: Control Point Information, Marking Point Information, View Panel and Photos Preview Panel The control point information bar displays the point information of the imported control point, and the marking point information bar displays the marking point information of each control point. The table header information is shown in the table, as shown below.

The view panel includes the Block View, 3D View, and Control Points Record. Block View displays a 2D view of the photos and control points within the block. It is primarily used for selecting, locking, and unlocking control points.

3D View displays the spatial positions of control points, point clouds, and photos.

Control Points Record shows the point records collected in the field, which are used to determine the actual location corresponding to the marked points. Users can refer to the point record to perform marking operations.

Photos preview panel shows photos to be marked and marking tools.

## Workflow ### **Import Control Points** Click **Import**, select the spatial reference corresponding to the control point file, select the separator, set the name, X, Y, Z, and click **OK** to import the control points.

### **Mark GCPs** Get3D Mapper supports manual marking points and intelligent marking points. **Manual Marking:** 1\) Select Control Points: In the Control Point Information Panel or Block View, select the control point to mark. Photos containing the selected control point will appear in the Photo Preview Panel. By default, photos with the point centered are displayed first, filling the panel in a tiled layout. 2\) Adjust Photo Display: The number of photos displayed per page can be adjusted. For example, if 4 photos are set per page, they will be displayed in an appropriate size. 3\) Mark Control Points: Photo names are highlighted with a yellow border. Selected photos are marked with a blue border. Hold the **Shift** key and **left-click** to mark the point. The marking position is confirmed based on field data collection. After marking, the photo name changes to a green border, and marking details appear in the Marking Information Panel. Once two photos are marked, a red prediction box will appear in subsequent photos, guiding the marking process. Press **D** to switch to the next page. {% hint style="warning" %} For optimal accuracy, it is recommended to mark approximately **30** photos per control point. {% endhint %}

**Intelligent Marking:** 1\) Initial Marking: Mark two photos manually for the control point. 2\) Intelligent Recognition: Click **Intelligent Recognition**, and the software predicts the corresponding positions in other photos. Photos with successful predictions are marked with a green border. Those without predictions remain with a yellow border and require manual marking.

3\) Check and Confirm: Verify the results on the current page. Adjust positions as needed. Click **Confirm Position** to save the markings to the Marking Information Panel. After confirming positions, the predicted points will change to red.

4\) Repeat for Remaining Photos: Navigate to the next page and repeat the steps until the required number of photos is marked with satisfactory precision. Some of the common shortcuts for Mark GCPs is shown:

### **Save Marking Results** After completing the marking, close the marking panel and save the edits to the block file. ### Submit AT After editing control points, click **Submit AT** and submit the absolute orientation. After AT processing( absolute orientation), continue submitting 3D reconstruction according to the workflow.

## AT Constraint **Usage:**\ For AT results generated from non-georeferenced data (relative orientation), a new *Constraints* tool is available under the Edit Control Points module.\ This allows you to add geometric or spatial constraints by linking control points to improve accuracy, correct deviations, or ensure geometric consistency.\ Create tie points by manually marking the same feature on multiple photos. **Steps:** 1. Mark at least 2 tie points. 2. Click *Add Constraints* to open the Constraints interface.

3. Select the constraint type.

Supported types: * **Scale Constraint:** Define the distance between two tie points to correct the model scale (e.g., building width, paint mark spacing).

* **Planar Constraint:** Force three tie points to lie on the same plane and align with a chosen coordinate axis plane (e.g., level ground or vertical wall).

* **Orientation Constraint:** Align the direction between two connection points parallel to a specified axis.

4. Set parameters, and click *Apply* to preview. Click *Reset* to revert to the original AT result. When closing, you will be prompted *“Save AT?”* Click *Yes* to apply the constraint to the block, or *No* to discard changes.