Usage
Used during the aerotriangulation of a block, user tie points can improve aerotriangulation accuracy and help the aerotriangulation in case of large baseline and ambiguous pattern. In most cases, user tie points are not required, because ContextCapture can cope with using only automatically generated tie points. User tie points should be used only to solve aerotriangulation issues. In all cases, before acquiring user tie points, we recommend to run a first aerotriangulation.
Improve photo position
Some repetitive elements in photos can cause a photo to not be properly positioned.
By defining points that represent the same position in different photos, you can guide the aerotriangulation process towards to correct photo positioning.
Group aerotriangulation components
Sometimes the aerotriangulation cannot connect all the photos due to a too large baseline or scale difference between some images.
With user tie points defined across the picture set, the multi-pass aerotriangulation mode is able to stitch the pictures together. To enable aerotriangulation multi-pass mode, from aerotriangulation settings, set "Component construction mode" to "Multi-pass".
At least 3 user tie points must be defined in 4 images (2 measures in each component that you want to fuse).
Adding user tie points increases components connection chances, but the connection is never guaranteed.
Add positioning constraints
Positioning constraints are priors based on user tie points to provide scene origin/scale/orientation. Positioning constraints are used to perform a rigid registration of the block during aerotriangulation.
See also constraints.