Generating a residual report for points

The residual report helps you determine if the math-model solution is good enough for your project. Residual errors do not necessarily reflect errors in the GCPs or TPs, but rather the overall quality of the math model. In other words, residual errors are not necessarily mistakes that need to be corrected. While they may indicate bad points, generally, they simply indicate how well the computed math model fits the ground control system.

Note: Depending on your selected math model, some features, such as the RPC adjustment order list, may be unavailable or vary in function.

To generate a residual report for points

Under Residual Units, click the measurement unit that you want displayed in the report.
In the table, the Res Z column is displayed only when Ground units is selected. Only values for TPs and GCPs are displayed, and the values are always in meters.With a mono GCP, no value is displayed.
When available, in the RPC adjustment order list, click the order you want to use.
This list displays only for a project using a rational function (RPC). Changing the RPC adjustment order will change the adjustment order for all photos in the project. For more information on RPC adjustment, including each available order, see Understanding RPC adjustment order
When available, in the Polynomial order list, click the order you want to use.
This list displays only for a polynomial project.
Under Show Points, select how you want to display points.
You can select or clear one or more check boxes, as necessary, according to the various point types you want to display.

To display the GCPs that appear on more than one image, click Stereo GCPs only.

For more information about active and inactive points, see Making points active and inactive
Under Show In, do one of the following:
- To display the points of all active images in the project, click All active images.
  For more information about active and inactive images, see Making images active and inactive
- To display the points of a specific image in the project, in the Image ID column of the table, click the image you want, and then under Show in, click Selected image.
Under Sort by, do one of the following:
- To order the residual errors from the highest to the lowest value, click Residual.
- To order the normalized residual errors from highest to lowest probability of error that is not noise, click Data snooping.
  This feature is available only when the math model calculation is up to date.
To select a specific group of points in the table, under Automatic Point Selection, type or select:
- The number of points with the highest RMS error to select in the Points by residual box.
- The maximum percentage of points to select per image in the Maximum percent of points/image box.
- In the Lowest selectable residual box, type or select the lowest value of the RMS for points to select.
Edit the points, as necessary.
Do one or more of the following, as applicable:
- To automatically select points with the highest residual value, under Automatic Point Selection, click Select.
- To view a tabular report of the selected points, click Selection Report.
- To compute the solution for the rigorous math model, click Compute Model.
- To save the report to a text file, click Print to File.
  In the Save Text Report dialog box, type the path and file name of the file (.txt) in the Report File box, or click Select to choose a location. To add the report to an existing file, click Append, or to replace or create a file, click Overwrite.
Note: Any changes made to GCPs or TPs renders the current math model out of date. When a math model is out of date, all information related to that model, such as residual errors, is also out of date. OrthoEngine indicates that a model is out of date by displaying the outdated information in red text and showing a red status message that reads, "Model needs recomputing". To maintain an updated model, in the Residual Errors window, click Compute Model. After the model has been updated, the information is again displayed in black text.