Block adjustment

Available with Advanced license.

When an ortho mapping workspace is created, the next step is to perform block adjustment using the tools in the Adjust and Refine groups. The adjustment tools encapsulate operations of computing match points (tie points) from overlapped images, performing triangulation calculations, and coarse orthorectification. The adjustment tools use an algorithm and processing procedure that are suitable for each ortho mapping workspace type. For instance, the algorithm performs RPC triangulation for satellite images and frame triangulation for aerial images. The parameters used in the adjustment computation can be defined on the Adjust dialog box. The adjustment quality report can be viewed using the Quality Report tool.

Adjust tool

The Adjust tool is used to perform block adjustment of the image collection in the current ortho mapping workspace. The processing can be done at image source resolution—computing tie points from source images, then performing triangulation using the computed tie points, or at a coarse resolution to estimate exterior image orientations and improve GPS location. Drone and scanned aerial images normally come with poor-quality or no exterior orientations and coarse GPS information. In these cases, an initial adjustment will be performed at a coarse resolution—a user-defined pyramids level is used to estimate the image orientations, and then an adjustment will be performed at the source resolution. The tie points generated at the initial adjustment will be used to seed the tie point computation and triangulation calculation at the source resolution in the refined Adjust calculation. Having pyramids built for the image collection ahead of time or during ortho mapping workspace creation will reduce the time of the initial adjustment process.

Adjustment options

The parameters used to compute the block adjustment are defined on the Adjust dialog box . These include tie point density, relative accuracy of source imagery, computed adjustment points, and other parameters as described below. The appropriate set of parameters is presented on the dialog box depending on the type of workspace specified. For example, the parameters presented for a satellite imagery workspace differ from those specific to drone imagery.

Reset tool

The Reset tool returns the workspace to the previous selected state. This allows you to change adjustment parameters, reprocess the image collection, and refine your results. Use the Reset to Initial option to return the workspace to the initial, unadjusted state. Use the Reset to Estimated option to return the workspace to the quick adjusted state, or the Reset to Full Adusted option to reset the workspace to the previous full adjustment. To preserve the current ortho products, save a copy before running reset.

Refine adjustment

To further improve the adjustment accuracy with ground reference, you can add ground control points (GCP) using the Manage GCP tools in the Refine group. The adjustment quality can be viewed from an adjustment report using the Adjustment Report tool. To view adjustment information for individual images, including tie point coverage, tie point count, and the root mean square (RMS), use the Image Inspector in the Review group. This allows you to filter or delete images based on the adjustment statistics or to activate images that were not used in the adjustment. If the adjustment errors are larger than expected, use the Manage Tie Points tools to check your tie points.

Layer rendering

Once you have performed an adjustment, the Solution Data and Control Points layers will be populated in the Contents pane. To adjust layer symbology, right-click the layer, select the layer symbology, and choose a method for displaying the associated points. Layer groups can also be turned on and off.

Manage Tie Points

The Manage Tie Points pane is used to view and edit tie points and point sets for selected images. Run the Analyze Tie Points tool to generate a coverage feature class and an overlap polygon feature class, which are added under the QA/QC Data entity and included in the Image Inspector table. The two feature classes help you understand whether you have enough tie points and where you need to add more tie points. Use the Tie Point Editor to filter, add, and remove tie points or point sets in individual images. To add tie points for specific areas within your image collection, or recompute tie points using different parameters, run the Recompute Tie Points tool .

These tools update the control points in the ortho mapping workspace. Run the Adjust tool again to incorporate changes and update the image collection. For the full workflow using the Tie Point Editor and Image Inspector, see Manage tie points in an ortho mapping workspace.

Icon	Name	Description
	Add Images	Add image.
	Add a point set	Create a point set from the selected tie points.
	Add a tie point	Create a tie point by clicking a location in an image in the Preview pane. Then add the corresponding tie points in the other images.
	Delete all filtered point sets	Delete all listed point sets.
	Delete point set	Delete the selected point set.
	Delete tie point	Delete the selected tie point.
	Dynamic Range Adjustment	Adjust the stretch using only the data contained within the image display window.
	Center to tie point	Center the viewer to the tie point.
	Filter point sets	Filter point sets by selection, current map extent, and attributes.
	Flash tie points in the point set on Map	Highlight the selected point set on the map.
	Select filtered point sets on map	Highlight the filtered point set on the map.
	Show solution point	Show the solution point in viewers.
	Synchronized zoom in	Adjust all image views to the scale of the first image.
	Synchronized zoom out	Zoom out to a fixed scale for all images in the preview.
	Zoom	Zoom to the full image extent.

GCP Manager

The GCP Manager pane is used to add, edit, and manage your control points so they can be used in your ortho mapping project. If your GCP Manager does not have any rows in the table, it means that there are currently no GCPs or tie points associated with your ortho mapping project. If you already have GCPs saved in a file, you can import them using the Import GCPs button . If you do not have a GCP file, you can create GCPs using Compute GCPs , which is under the Manage GCPs drop-down menu. You can also create GCPs and tie points using the Add GCP or Tie Point tool .

The table below lists all the tools you can use within the GCP Manager pane. For the full workflow to add GCPs, see Add GCPs to your ortho mapping workspace.

Icon	Name	Description
	Add GCP or Tie Point	Create a GCP by clicking a location on the map. Then add the corresponding tie points in the GCP Manager viewer.
	Clear Links	Delete all the links between the images, for the selected ground control point.
	Delete GCP	Delete the selected ground control point.
	Delete All	Delete all the ground control points.
	Import GCPs	Import a GCP file from a text file, a CSV file, or a feature class. The feature class must have x,y defined in either the Shape field or in two separate fields.
	Export GCPs	Export the GCPs to a file.
	Filter	Switch the filter toggle button to show all the GCPs, or only the GCPs in the current map display. The default is to show all GCPs. Click the Filter button to filter out GCPs that are outside of the current extent. This can be used when GCPs are outside of the area of the image collection, or used to focus on one GCP within the area of interest.
	Refresh	Refresh the GCPs in the GCP Manager and the map display. This is useful when you make an edit to a GCP, to make sure that the manager and the map display are still in sync.
	Zoom	Zoom to the full extent of the image.
	Show GCP	Display the corresponding GCP location in the image display window.
	Dynamic Range Adjustment	Adjust the stretch using only the data contained within the image display window.

To temporarily disable a GCP, change the XY Accuracy and Z Accuracyfields to <NA>.

To change a GCP into a check point, right-click the GCP row in the table, and choose Change to Check Point.