Available with Advanced license.
Available for an ArcGIS organization with the ArcGIS Reality license.
The parameters used in computing the block adjustment are defined in the Adjust window. The available adjustment options depend on the type of workspace defined when you set up the Reality mapping project. For example, triangulation is performed using EXIF data collected with drone imagery.
Adjustment options for drone data
Higher in-strip and cross-strip aerial image overlap is recommended for better block adjustment and product generation results. The block adjustment settings specific for drone imagery 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 the project area and the processing parameters for the collection before running the more accurate, refined adjustment at the source image 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.
Fix image location for high accuracy GPS
This option should be used if your data was captured using high accuracy GPS, such as Real Time Kinematic (RTK) or Post Processed Kinematic (PPK).
Perform camera calibration
Automatic camera calibration computes and improves the camera’s geometric parameters, including interior orientation and lens distortion, while determining image orientation and image ground coordinates. If the camera has not been calibrated, as is the case of many cameras for collecting drone imagery, it is recommended that you check all the following options to improve the overall quality and accuracy of bundle block adjustment. All options are checked by default. For more information about calibration parameters, 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
- Fix Image Location for High Accuracy GPS—This option is used only for imagery acquired with high-accuracy, differential GPS, such as real-time kinematic (RTK) or post processing kinematic (PPK). If this option is checked, the process will only adjust the orientation parameters of the imagery and leave GPS measurements fixed. Additionally, ground control points (GCPs) are not required when this option is checked. GCPs will be marked as check points in the adjustment.
Camera calibration is performed during block adjustment to improve the camera parameter accuracy. For camera calibration, the image collection must 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.
Use orientation from metadata
When checked, the exterior orientation information embedded within the image EXIF will be used as initial values in the block adjustment process.
Compute posterior standard deviation for images and solution points
The following options enable users to compute the standard deviation for each image exterior orientation parameters and solution point coordinates.
- Compute Posterior Standard Deviation for Images—The posterior standard deviation of solution points after adjustment will be computed. The computed standard deviation values will be stored in the Solution table.
- Compute Posterior Standard Deviation for Solution Points—The posterior standard deviation of each image location and orientation after adjustment will be computed. The computed standard deviation values will be stored in the Solution Points table.
Reproject tie points
A part of the adjustment process includes computing and displaying each tie point at its correct 2D map location. This is an optional step that only supports the visual analysis of tie points with the 2D map view. Following adjustment, the Reproject Tie Points option in the Manage Tie Points drop-down menu must be used.
Note:
When working with large projects with over a 1000 images, this step can be skipped to reduce adjustment processing duration, without any adverse impact to the adjustment quality.
Tie Point Matching
Tie points are points that represent common objects or locations within the overlap areas between adjacent images. These points are used to improve geometric accuracy in the block adjustment. The Tie Point Matching category in the Adjust tool includes options to support the automatic computation of tie points from overlapping images.
Image Resolution Factor
This parameter is used to define a resolution at which match points are computed and the initial adjustment is 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 image 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 coarser resolution.
Image Location Accuracy
Image location accuracy indicates the accuracy level of the GPS data collected concurrently with the imagery and listed in the corresponding EXIF data file. The values consist of four airborne GPS accuracy levels that are used in tie point calculation to determine the number of necessary overlapping images. For example, when the accuracy is set to High, the algorithm uses a smaller neighborhood to identify matching features in the overlapping images.
| Setting | Description |
|---|---|
High | The GPS accuracy is 0 to 10 meters. A maximum of 4 x 3 images are used for tie point matching. This is the default setting. |
Medium | The GPS accuracy is 10 to 20 meters. A maximum of 4 x 6 images are used for tie point matching. |
Low | The GPS accuracy is 20 to 50 meters. A maximum of 4 x 12 images are used for tie point matching. |
Very Low | The GPS accuracy is more than 50 meters. A maximum of 4 x 20 images are used for tie point matching. |
Drone imagery tutorial
For a tutorial on the complete drone imagery workflow, see Tutorial: Create drone imagery products in ArcGIS Reality for ArcGIS Pro.