Orthomosaic generation (planar projection) : Helpdesk Portal

This solution describes the process of terrestrial image data processing and orthomosaic generation in planar projection. Planar projection-type may be useful for projects concerning facades or other similar vertical surfaces. The main stages of processing are the same as when building a 3D model.

Tutorial includes the following steps:

Create masks
Align Photos
Build Point Cloud
Build Model
Build Orthomosaic (planar projection)
- Method 1: Current View
- Method 2: Markers

Add Photos

1. To add photos select Add Photos... command from the Workflow menu (Workflow > Add Photos...).

2. In the Add Photos dialog browse the source folder and select files to be processed.

Create masks

Recommended masking all irrelevant elements on the source photos. Masks in Metashape are represented by contours bounding certain image regions. Modification of the current mask is performed in Photo View through adding or subtracting selections.

Find more information in the tutorials:
Working with masks 
Automatic masking from the model
Automatic background masking using custom script

Align Photos

1. Select Align Photos... command from the Workflow menu (Workflow > Align Photos...).

2. Set the following recommended values for the parameters in the Align Photos dialog:

3. Click OK button to start photo alignment.

Build Point Cloud

If you don't need a point cloud as a result, then you can skip this step and use the grid option.

1. Select Build Point Cloud... command from the Workflow menu (Workflow > Build Point Cloud...). Set the following recommended values for the parameters in the Build Point Cloud dialog:

2. Click OK button.

Points from the point cloud can be removed with the help of selection tools and Delete/Crop instruments located on the Toolbar.

Also you can find useful information in our article: Advanced Selection tools for Point Cloud and Mesh

Build Model

1. Select Build Model... command from the Workflow menu (Workflow > Build Model...). Set the following recommended values for the parameters in the Build Model dialog:

if at the previous stage - Depth maps was built and save in project, we recommend using the parameter - Reuse depth maps.

2. Click OK button to start building geometry.

Build Orthomosaic (planar projection)

Metashape Pro allows to project of the orthomosaic onto a plane set by the user, providing that Model is selected as the Surface type. The projection plane can be determined by a set of markers (if there are no 3 markers in the desired projection plane it can be specified with 2 vectors, i. e. 4 markers).

We suggest the reconstruction of orthomosaic in a planar projection mode using the two following methods: Current view and using Markers.

Build Orthomosaic procedure can be performed only for projects saved in PSX format for chunks with the existing model or DEM.

More then one instance of Orthomosaic can be stored in one chunk. In case you want to save current Orthomosaic instance and build new one in current chunk, right-click on Orthomosaic on the Workspace pane and uncheck Set as default option. In case you want to save current Orthomosaic instance and edit its copy, right-click on Orthomosaic and choose Duplicate option.

Method 1: Current View

1. Select the Build Orthomosaic... command from the Workflow menu (Workflow > Build Orthomosaic...).

2. In the Build Orthomosaic dialog box select parameters for building orthomosaic. We selected - Current View for building Orthomosaic.

3. Click OK button when done.

4. The progress dialog box will appear displaying the current processing status. To cancel processing click Cancel button.

Method 2: Markers

To set axes using markers, you should add markers to the project. You can place markers on the surface of the model and outside it.

Markers that will be located outside the model surface, the model should be georeferenced or have a scale bar (how to create scale bar instance: Coded targets and Scale bars). Then after creating a marker, you can enter the coordinates of the marker on the Reference pane.

We set markers on the wall of the building without inputting their reference coordinates.

Open Model or Point cloud on the Model view and place markers on the object that will define our axes (select Add marker command from the context menu). We used 3 markers to define the projection plane.

For more accurate marker placement we recommend to adjust markers' projections on the images in the Photo view mode.

In case it is required to get an orthomosaic of a part of a building (for example, the left part of the building facade), you can either change the Bounding box or set the area of interest in the Build Orthomosaic dialog window (enable checkbox - Setup boundaries and choose a region). The latter option is applicable for georeferenced projects only.