The parameters used in computing the block adjustment are defined in the Adjust window. The adjustment options available depend on the type of workspace you defined when you set up your ortho mapping project.
Adjustment options for scanned aerial data
The block adjustment parameters for scanned aerial photographs are described below.
Quick adjust at coarse resolution only
If this option is checked, adjustment is performed at a coarse, user-defined resolution. This coarse adjustment is done quickly and allows you to review the data coverage for your project area and the processing parameters for the collection before running the more accurate, refined adjustment at the source imagery resolution. For example, when you collect data in the field, you can use this option for an initial assessment of the adjustment. Then run Adjust again to compute the refined adjustment. If this option is not checked, tie points are computed at the source image resolution, and triangulation is performed using the computed tie points.
Perform Camera Calibration
Automatic camera calibration computes and improves the camera’s geometric parameters, while determining image orientation and image ground coordinates. Select these options to improve the overall quality and accuracy of bundle block adjustment. For more information on calibration options, see Camera table schema.
- Focal Length—Refines the focal length of the camera lens
- Principal Point—Refines the principal point of the autocollimation
- K1,K2,K3—Refines the radial distortion coefficients
- P1,P2—Refines the tangential distortion coefficients
Note:Automatic camera calibration requires that your image collection have an in-strip overlap of 60 percent or more and a cross-strip overlap of 30 percent or more.
Blunder Point Threshold (in pixels)
Tie points with a residual error greater than the threshold value are not used in computing the adjustment. The measurement unit of the residual is pixel.
Note:Higher in-strip and cross-strip aerial image overlap is recommended for better block adjustment and product generation results.
Image Resolution Factor
Use this parameter to define a resolution at which match points will be computed and the initial adjustment performed. The range of values is between full resolution and 8 times the resolution of the source imagery.
The default value of 8 times the source resolution is suitable for most imagery that includes a diverse set of features. A smaller value, such as 4 or 2, can be used for imagery with ubiquitous features, such as sand, water, or agricultural areas, where match points are difficult to compute at coarse resolution.
Image Location Accuracy
Image location accuracy indicates the accuracy level of the airborne GPS data collected concurrently with your imagery. The values consist of four levels that are used in the tie point calculation algorithm to determine the number of images in the neighborhood to use. For example, when the accuracy is set to High, the algorithm uses a smaller neighborhood to identify matching features in the overlapping imagery. However, airborne GPS may not have been collected with historical imagery, so the location accuracy for scanned aerial images is typically low or unknown.
The image location accuracy is 0 to 10 meters.
The image location accuracy is 10 to 20 meters.
The image location accuracy is 20 to 50 meters. This is the default value.
The image location accuracy is more than 50 meters or is unknown.
Scanned historical imagery tutorial
For a guided tutorial on the full scanned imagery workflow, see Create Scanned Aerial Imagery Products in ArcGIS Pro.