Merge Models in iTwin Capture Modeler

How to merge models in iTwin Capture Modeler

This article explains how to merge a high resolution (ground) model with a model «10 cm» (air) in iTwin Capture Modeler.

The user must merge photos taken from different sources, i.e. the data set was acquired from images taken using a digital SLR camera and a drone.

Treat Aerotriangulation «Standard» on the high-resolution (ground) data set.
On this aerotriangulated block, open the anchor point editor.
Identify points of interest that can also be viewed in the model «10 cm» (air) and click on it in at least two photos to get their estimated coordinates. Save these values to a GCP import file.
Open the 10 cm aerotriangulated block.
Open ControlPoints editor.
Add the newly identified points and their coordinates to the GCP tab.
Direct them into images of « 10 cm » and record them.
Run an AT on the block « 10 cm » using these GCPs for adjustment.
Your two blocks (high resolution and « 10 cm » ) are now properly georeferenced and ready for the fusion stage.

Select your two blocks in the project column> Right click> Merge.

Create two reconstructions.
The most important thing here is tile. Since you have different resolutions, you will probably have to produce tiles of different sizes.
In the first (Reconstruction 1), you will only produce tiles based on aerial images, so set a tile size based on this data set.
Produce only tiles surrounding the area of interest (covered by ground imaging).
In the second reconstruction (Reconstruction 2).
Define exactly the same tile SRS as for Reconstruction 1.
Define exactly the same source of paving as for Reconstruction 1.
Define a tile size that is a multiple value of Reconstruction 1 tiles (e.g. if Reconstruction 1 has 160m tiles, set it to 160m or 80m, 40m, 20m,...for your data and computer resources).
Produce tiles that cover the area of interest and surrounding areas to extend production to a Reconstruction tile 1.

On the above image:
– Blue: area covered by aerial imaging
– Black: reconstruction tile 1
– Red: zone of interest of the high resolution model
– Yellow : Enclosing box of your Production 2 area
– White: smaller tiles than you have to produce
In addition to this, you must also take care to produce Production 1 and Production 2 exactly in the same SRS (same SRS and same origin in the production parameters).
Once your two productions are complete, use the S3C-Scene-Compose to merge them.