Overview

Our Align to Control tool aligns Looq data products to field measurements, referred to as “Ground Control Points”. The wizard is a guided process supporting file import, manual point selection, residual (fitness) preview, and finally a rigid-body transformation (shift, rotate, scale) of the point cloud, ortho, and panoramic image locations.

How to use Align to Control

The Align to Control tool can be found under the qSurvey menu in the 3D view. Clicking on the icon will bring up the point manager. Align to Control results for each capture can be saved and reviewed at any time using the point manager. The first step in the process is to import field measurements from a file, or add them manually by typing in the individual coordinates for each point.

The following is an example of a .CSV file that could be imported:

Select File: Select your file from a local folder or drag and drop it in. Map the columns from your file to the corresponding coordinate fields in the webapp. If your file does not have headers in each of the columns with values, make sure the "Include Headers" option is unchecked.

Import: Click "Preview" to review the imported data. If you want to make changes or if you need to start over, click “Cancel” and click "Reset Columns" to clear all entries. After verifying the data, click "Confirm" to complete the import. Your imported points will now appear in the Point Manager. The imported points are tied to the capture that was open at the time of import. They will be visible whenever working with that specific capture, but not by other captures in the site. This process must be done separately for every capture in a site. If the control points share the same coordinate system as your point cloud, they will appear correctly on the map; if not, they may not align perfectly, but you can still proceed.

Marker Selection: To use a field measurement for alignment, you must manually select its associated location within the point cloud using the “ATC Wizard”. Begin this process by clicking the Point Selector button and then navigate to its associated location in the point cloud. Click on the corresponding point in the point cloud to make the association between the field measurements (ground control) and Looq data. If you're not satisfied with your selection, click "Reset" to choose again. Once you're satisfied, click "Continue" to proceed to the next point. Repeat this process for the rest of the points that you want to include in the alignment. If you cannot find a corresponding point or wish to skip it, click "Skip," and this point will be excluded from the alignment process. You need at least 3 points to proceed.

Control Point vs Check Point: You now have the ability to select a point as either a Control point or a Check Point. They are both points that have been surveyed or have been imported as a known point, but they are used different in the ATC workflow. 

• Control Point - the point is used as a constraint in the adjustment
• Check Point - the point is not used as a constraint, but used to independently validate the quality of the adjustment

Both point types show residuals from the adjustment and in the accuracy report. 

Complete Alignment: After completing the manual selection process, click "Finish," and when prompted, click "Align to Control". Click “Yes” when asked if you wish to save the points to the Point Manager. The Align to control tool will show both the offset between the control points and the selected points and the estimated post-alignment residual errors. If you are not satisfied with the estimated residual values, you can cancel the process before running to add or remove specific locations. To apply the transformation, click “Yes”. After confirming, the tool will now start processing and it should finish within 1-2 hours. The control points are saved and tied to that capture, and will be accessible when opening it in the future.

Resetting the ATC workflow

To undo any of the align to control changes, click revert to original in the Points Manager. This will restore all of the data products associated with the capture to their original state. The “revert” progress can be monitored in the notification pane.

Exporting the ATC Accuracy Report

In the ATC side panel, you now have the option to download a pdf report that outlines the accuracy reporting for the ATC workflow. The report includes the information about the capture, along with the points that were used as control or check points in the adjustment.