Use control points
To use control points in an alignment, they must be measured in the images that observe them using the Image Measurements tool on the Alignment tab.
You can import control points, their manual image measurements, and their control point roles from Inpho .prj files if available.
Tip:
Run an alignment before measuring control points. This increases the number of point suggestions in the image measurement tool, making manual measurement clearer and faster.
Learn more about the image measurement tool in this video playlist
Measure control points
To measure control points, complete the following steps:
In the Project Tree pane, select the alignment containing the control points you want to measure, and click the Alignment tab.
On the Alignment tab, click Image Measurements
.The Image Measurements tool appears.
The Map view gives you an overview of the location of the ground control points, check points, and manual tie points in your alignment.
Tip:
For a clear overview, click Filter
to display only the point types you currently need. You have the option to filter for ground control points, check points, and manual tie points and display their point labels. You can also distinguish between displaying measured or unmeasured points. If you processed the alignment beforehand, you can visualize the automatic tie points as well.Select the point you want to measure by completing any of the following two options:
Click the point on the map.
Click the point row in the table to select it.
The images containing the chosen point are listed in the Image table. The first image in the table is shown in the Image viewer.
Tip:
You can change the image viewer layout using the Layout button. You can display one
, four 
, or nine 
images at the same time. The zoom-level of the image viewers is synchronized. By selecting an image row in the Image table, the corresponding image in the Image viewer is highlighted, and vice versa.Note:
If you don't want to use a control point in the alignment, click Enable/Disable
to exclude the control point from the alignment process. A crossed gray ring 
appears indicating the control point is excluded from the alignment. Click Enable/Disable again to include the control point in the alignment.Tip:
The Columns
option allows you to filter which columns of the control point table to see. You can display the 3D point coordinates, reprojection errors, residuals in 3D space, as well as the number of cameras that captured the point.In the Image viewer, click the exact location of the control point in the image, and go to the next image or image set.
Note:
To go to the next image, you can use keyboard shortcuts, use the navigation buttons on the toolbar, or click the image in the Image table.
Repeat this step for all the images in the table. Alternatively, you can set one of the measurements as a template to request image measurement suggestions in the remaining images.
Note:
You must make at least two image measurements for a control point to be used in an alignment or to set an existing measurement as template.
Tip:
To change a measurement, you can click a new location in the image or remove the measurement by clicking the Remove button
on the toolbar.Repeat steps 3 and 4 for each control point you want to include in the alignment.
The control points are measured and ready to be used.
You can process the alignment once all the necessary control points have been measured.
Request image measurement suggestions
Image measurement suggestions are generated using an image template, the image orientations, and the previous image measurements.
To request and use image measurement suggestions, complete the following steps:
After two or more manual measurements are made, select one of the images with a measurement in the Image table and click Find Suggestions
on the toolbar.A template symbol
appears in the Image table, in the Status column. Suggestion symbols 
appear in the Status column where image suggestions are generated.Note:
Suggestions are only generated if the reprojection error of the measurements is small.
Click the row of an image with a suggestion to see it in the Image viewer.
Click Accept
or press the Spacebar to accept the suggestion.Note:
You can click Accept All
on the toolbar to accept all available suggestions.To use a different image measurement as a template to get more suggestions, select the new image in the Image table and click Find Suggestions
on the toolbar.New measurement suggestions are generated based on the new template.
Keyboard shortcuts
You can use keyboard and mouse shortcuts to navigate, browse, and measure points.
Navigation
For help with navigating in the map and image viewer, use the following keyboard shortcuts:
| Keyboard shortcut | Description |
|---|---|
| Middle drag / C + click | Pan |
| Middle roll wheel | Zoom in and out |
Image measurements
Use keyboard shortcuts in the Image viewer of the Image Measurements tool.
| Keyboard shortcut | Description |
|---|---|
| Click | Make an image measurement. |
| Shift+click | Remove an image measurement. |
| Spacebar | Accept suggestion and go to next image. |
Browse tables
Use keyboard shortcuts for help with browsing tables in the Image Measurements tool.
| Keyboard shortcut | Description |
|---|---|
| F | Go to the next image in the Image table. |
| B | Go to the previous image in the Image table. |
| Shift+F | Go to the next point in the points table. |
| Shift+B | Go to the previous point in the points table. |
Role of a control point
A control point can have two roles: It can be used as a ground control point (GCP) and a check point (CP). GCPs are used in the alignment processing. CPs are used to assess the quality of the alignment results.
Note:
The role of a control point is specified per alignment. This allows you to use different roles for the same control points in different alignments.
If control points are imported from an Inpho .prj file, the roles of the control point are imported as well. In all other cases, control points are assigned the GCP role by default.
Change the role of a control point
There are two options to change the point role in the Image Measurement Tool:
Change point role from map.
Click the point on the map.
Right-click anywhere in the map view to display the context-menu.
Click Set Role To Ground Control Point
or Set Role To Check Point 
.
Tip:
You can select multiple points at once in the map by holding Shift while selecting the points or by using the Select
tool to draw a shape around the points.Change point role from table.
Select the point role from the Control Points table.
Click the Set Role
drop-down menu.Click GCP or CP.
Tip:
Hold the Ctrl key and click an individual control point to select or deselect it. Hold the Shift key and click to select and deselect groups of control points.
The role of the selected control point is updated and visible in the Control Points table.
You can process the alignment to update the alignment results.
Image measurement status
A control point must have at least two image measurements to be included in the alignment process. The status of a control point is represented by a symbol that indicates the number of images it has been measured in.
The image measurement status symbols indicate the following:
—A point has fewer than two image candidates and cannot be used in an alignment.
—A point has two or more image candidates but no image measurement.
—A point has two or more image measurements.- —A disabled point that will not be used in alignment.