Sometimes users may have a problem with surface stress iTwin Capture Modeler. This can be caused by incorrect alignment of images. The altitude values in the metadata are not at all good and this prevents the AT from finding a good orientation: the scene will be folded, so the constraint will be moved accordingly.

The alignment of images can be analyzed when adding images to CC. To do this, add images, then click on the 3D view. From there you can see that, in this case, some images are at a bad altitude.

To solve the problem, you can place GCP by hand to recover a good georeference.

The procedure is as follows:

• Create Block> Load Images
• Submit AT by selecting Vertical as a positioning mode> you will get a good orientation but the scene is not georeferenced.
• Open Google Earth and make sure the following settings of Tools> options are enabled: Decimal degrees for « Show lat / long » and Metres for « Units of measurement ».

• Now choose 4 relevant points, then note their coordinates.

• Go back to CC and click on theSurvey tab , set the SRS to WGS84 + EMG 96 as a geoid, then create the 4 GCP corresponding to these points (indicate each GCP in at least 4 images).

• Now submit the AT again and choose the positioning mode « Use checkpoints for rigid recording ».

• You should have a georeferenced scene. You can now apply a surface constraint.

• From Google Earth, trace a simple polygon around the corresponding area.

• Once created, open the properties of the polygon, click the tab Altitude and Set the value of the right altitude on Absolute. You can see this value in the bottom right corner of Google Earth. Here, the water altitude is 75m.

• In iTwin Capture Modeler, create a new reconstruction and import constraint.