Deriving TerraMatch correction values from images
Images of the road surface can be used to define tie points from which TerraMatch corrections values can be derived. The tie points can be created from control points drawn into the design file (absolute control) or by placing them in images of different drive paths (relative control). The tie points are of Tie point types “Known depth” or “Depth”. These tie points at regular distances along the road allow the derivation of fluctuating correction values for TerraMatch.
The workflow involves TerraMatch functionality which is not described here. For more information refer to the TerraMatch Users Guide available at the Terrasolid webpage.
1. Create TerraPhoto a camera calibration file for the camera that sees the ground best (downward-looking camera) using the commands in the TerraPhoto camera dialog.
For the present workflow, only images that see the road surface as vertical as possible are needed. However, it is also possible to create the camera calibration files and image list for all cameras of the system and then reduce the image list to images captured by a downward-looking camera.
2. Define a mission with New mission command.
3. Import trajectories using Manage Camera Trajectories tool.
4. Create an image list with Compute list command.
3. Define an exterior orientation file format in Exterior orientation formats of TerraPhoto Settings.
4. Create an image list by importing exterior orientation files with Load list command.
If you use data from a Lynx system, the camera calibration files, the mission file, and the image list can be created automatically by importing the Lynx survey file. See Import Lynx Survey command.
5. Create thumbnail versions of raw images with Create thumbnails command.
6. Define tie points for adjusting the images to the laser data and for deriving TerraMatch correction values. This part of the workflow is described in detail in Section Ground control points for mobile ground-based projects.