This article describes the general processing workflow in Agisoft Metashape for the projects consisting of sub-sets acquired with the drone (nadir and oblique aerial images) and with the common hand-held digital camera. Additional recommendations related to the image acquisition scenarios are given.
Recommendation for shooting
When it is required to build the details model of such objects as buildings, complex structures, etc. it is reasonable to use the combination of terrestrial and aerial photography in order to avoid any blind spots. We suggest that you familiarize yourself with the following recommendations for shooting before planning the image acquisition scenario:
- Don't shoot from a single point. It is important to move with a certain step along the object side. When the stereo base (distance between neighboring camera locations) is small and the images are taken from almost the same point, it is difficult to get information about the depth. We recommend that to stay more or less at the same distance from the object, move parallel to its side and take images at the same height first, then you can use a tripod and move along the object to complete the next route at another height. However, it is important to keep sufficient overlap between images (both between the images from the same route and between the images from the different routes).
- We also recommend to minimize the time of image acquisition in order to avoid big differences between the shadows for outdoor shooting in sunny weather. It is optimal to shoot at noon and/or in cloudy weather.
- If you use markers, try to place them so that they can be seen from as many as possible cameras.
- If you are shootings using different camera models, we recommend to process all the subsets together. For better convenience, you can group the images by the camera model (select cameras in the Workspace pane and choose Move camera > New camera group from the context menu). The calibration groups will be formed automatically based on the camera model, image resolution, and focal length, but we still suggest to use a fixed lens or fix the focal length on a zoom lens, if it is used to take terrestrial images.
In our example, we processed images from the drone, smartphone camera, and digital camera together. The terrestrial images were taken while moving around the building with the handheld camera and smartphone, whereas the drone has captured oblique images of the building in order to have overlap with the terrestrial photos related to the facades, but at the same time cover the roof elements that are not seen from the ground.
- For a detailed drone survey, you can use the Plan Mission functionality of Metashape Professional.
Processing of images in Metashape includes the following main steps:
- Add photos;
- Align photos;
- Build Mesh;
- Build Texture.
The tutorial below describes these workflow processing steps and recommended parameters for the combined aerial and terrestrial image data processing in Agisoft Metashape Professional (actually, in a similar way the data can be processed in Metashape Standard, unless you are using markers or are interested in scaling and georeferencing the project in Metashape directly).
1. To add images select Add Photos... command from the Workflow menu.
2. In the Add Photos dialog browse the source folder and select files to be processed.
3. Operation can be repeated, if the source images are stored in different folders.
1. Select Align Photos... command from the Workflow menu.
2. In the Align Photos dialog box select the desired alignment options.
Since ground-based images most likely do not have measured coordinate information and due to the oblique aerial survey we strongly recommend to disable the Reference preselection option and use only Generic preselection.
3. Click the OK button.
4. The progress dialog box will appear displaying the current processing status. To cancel the processing click the Cancel button.
5. After camera alignment is finished, the estimated camera positions and a sparse point cloud will be displayed in the Model view.
Components A new feature has been implemented in the Metashape version 1.7.0. - Components. Some additional details about components can be found in the following article - Connected components in the camera alignment procedure. If some image subsets of the dataset are not aligned with each other, they will be grouped into individually aligned parts (so-called "Components"), which will be displayed in the chunk's contents of the Workspace pane:
To align components with each other manually use markers. To switch the display in the Model view to the desired component double-click on its label in the Workspace pane.
After all the components are aligned, select them in the Workspace pane and then use Merge Components command from the context menu.
1. Select the Build Mesh command from the Workflow menu. Set the following recommended values for the parameters in the Build Mesh dialog:
Depth maps based mesh generation is the recommended option for the scenes with small and thin elements, that should be preserved in the final model. Another option is to generate the dense point cloud (via Build Dense Cloud command) and then use the dense cloud source option in the Build Mesh dialog.
2. Click OK button to start building geometry.
1. Select the Build Texture command from the Workflow menu. Set the following recommended values for the parameters in the Build Texture dialog:
2. Click the OK button to start building texture.