Add a control point

In the registration process, adding control points is a very important step. Because Registration Layer and Reference Layer reflect the features of the same or partial spatial locations, it is necessary to add registration control points at the feature points of Registration Layer. At the same time, the homonym of the point is found in the corresponding feature position of the Reference Layer.

The essence of this process is to identify a series of control points (X, y coordinates) to link the location of the registered Dataset with the location of the Reference Data. A control point is a location that can be accurately identified in the registered Dataset and actual coordinates.

The accuracy of data registration is largely determined by the accuracy and number of selected control points and the distribution of these points. The following points should be noted when selecting control points:

Generally, the control points shall be the prominent map feature points with clear and fixed signs and easy to identify on the Registration Layer and Reference Layer, such as the intersection of roads, the trunk of rivers, the corner of fields, etc.;
Control points must be evenly distributed on the layer, otherwise the accuracy of registration is better in dense areas than in sparse areas. And can reflect the trend of the whole image through the control point;
The number of control points should be appropriate, not the more the better, and should be selected according to the actual situation. But also the number of corresponding registration algorithms.

Support the addition of control points through manual prick points and Import Control Points. The detailed description is as follows:

Prick point

In the Control Point Settings group of the Registration tab, click the Prick Point button, and the mouse status changes to the crosshairs;

Hint :

After the
Create New Registration is finished, the mouse status defaults to the prick point status. You can prick points directly in the Registration Window. You can skip the above steps.
Locate the control point in the Registration Layer, and click the left mouse button to complete a puncturing operation of the Registration Layer. It can be seen that the mouse click position is marked with a blue cross wire (by default, the current control point is selected). At the same time, the registration control point information is automatically added in the control point list, and its coordinate value is displayed in the control point list, that is, the contents in the source point X and source point Y columns.
Click the left mouse button at the same name point of Reference Layer to complete a pricking operation of Reference Layer. It can be seen that the mouse click position is marked with a blue cross wire (by default, the current control point is selected). At the same time, the reference control point information is automatically added in the control point list, and its coordinate value is displayed in the control point list, that is, the contents in the target point X and target point Y columns.

Caution :

If the coordinate information of several points in the Reference Layer is known, you can select Input Target Point Coordinates in the Context Menu to directly input the target point information after the second pricking.
Repeat the operation process of 2-3 steps to complete the pricking operation of multiple control points. According to the registration algorithm used in this example, at least 4 control points need to be selected, as shown in the following figure:

Import Control Points

Import Control Points refers to importing Point Datasets in the Current Workspace as registration points and reference points.

Function entrance

Registration tab-> Control Point Settings group-> Import button;
Registration Map window right mouse button-> Import Control Points option;
Registration Control Points List Window Right mouse button-> Import Control Points option;

Operating instructions