1 Components (optional).
2 Positioning, georeferencing.
1.1 General rules.
1.2 When to use Adjustment constraints.
1.3 When to use Final rigid registration.
1.4 Georeferencing using control points.
1.5 Georeferencing using photo metadata.
1.6 Georeferencing using laser scan point cloud.
1.7 Scaling using user tie-points and positioning constraints.
1.8 Use Targets (QR codes, Apriltags or ChiliTags).
3 AT settings.
3.1 Poses and tie points.
3.2 Optical parameters.
3.3 Other options.
3.4 User presets (advanced usage).
This option is only available if a partially complete AT (for which some photos remain not consolidated) has been completed on the photo block. For a partially complete AT, the 2 following settings are available:
Note: You can have an overview of the non-calibrated photos by doing the following:
Figure 1: option to display only non-calibrated (without component) photos in the 3D view
If control points are utilised in the block these will be set as an adjustment constraint by default, as they normally have a high level of accuracy.
If the images have pose metadata (geotags or imported pose data), ContextCapture set this as a rigid constraint by default, as most drones still have a ‘raw’ GPS.
This setting can only be used for the final Rigid Registration and will only scale the data (no georeferencing)
The following parameters have an incidence on how the photos will be automatically connected together using Automatic tie-points
Four main parameters are available plus the Advanced menu
The tie-points and photo poses are (re-)calculated.
The tie-points are (re)-computed but the image pose will be adjusted from the current one.
You can use this option when:
The engine is using the current main component, or for a first AT, the biggest subset that it manages to consolidate, and is gradually adding disconnected subsets of images to connect it to the main component.
Note: this option was called ‘Complete incremental engine’ in the previous versions
You can use this option:
The engine will keep the image pose and tie-points, and move straight to the final stage of the AT: scaling/georeferencing, this will accelerate the time taken to complete an AT.
The Advanced… button allows you to fine-tune the Poses and tie-points policies, it is recommended to modify these parameters only after you have tested the default AT settings.
The user can manually modify the images Position / Rotation and the tie-point policy.
The user can also manually modify the following parameters:
In this section, the user will define the policy for the photogroups optical parameters: focal length, principal point, distortions…
This is the default mode for all ATs. It will adjust all optical parameters (except ratio and skew) during the photos matching process.
The optical parameters values remain locked during the AT.
The Advanced… button allow you to fine-tune the Optical parameters settings. It is recommended to modify these parameters only once you have tested the default AT settings and requires a strong knowledge of the camera specifications.
This setting allows the AT engine to adjust the optical parameters in a broader range.
Note: this option is automatically enabled for a first AT without pre-defined optical parameters.
If targets have been placed on the scene during the acquisition, the corresponding target setting should be selected in this menu.
This option (enabled by default) is equalizing the images RGB information based on the AT correlation.
To have it applied in the 3D productions texture, you will have to leave the Color equalization mode on Blockwise, when selecting the Reconstruction Processing Settings.
SPLATS are small square elements generated for each tie-point at the last stage of the AT, to give a more intuitive overview of the 3D scene. This option is always enabled by default, but the user can disable this setting if they considers that they will be able to analyze the 3D view with the 3D cloud of tie-points only.
If a user wants to keep their own defined AT settings for later projects, they can save these in a user config file by using the Save button
There are other presets available in the ContextCapture installation folder. Press the button to retrieve one of these presets.
Below are a bit of details on theses presets
This robust engine is useful to get more photos consolidated on challenging datasets that is not possible the legacy AT engine (update 17 and previous), but it is not scalable. The current AT engine has proven to be both scalable and robust and as so this preset has a marginal interest now.
This preset skips the scene consistency check based on GPS tags (i.e for inaccurate GPS on small scene). It can be useful for:
Us this preset to keep two or more subsets in the AT results, that can’t be physically connected together. Important! The poses policy needs to be on KEEP or ADJUST WITHIN TOLERANCE.
This preset uses the former AT engine (update 17 and previous). This is for users who want to test their dataset with the former engine.