In Metashape Professional edition both structured terrestrial laser scans and unstructured aerial laser scans can be imported using Import Point Cloud (select File > Import > Import Point Cloud) command. All point attributes including structured information are now preserved while importing.
In this article the following topics are discussed:
- How to import laser scans data into project?
- Processing only terrestrial laser scans
- Processing terrestrial laser scans and images
How to import laser scans data into project?
To import laser scans data into Metashape 2.0 project its is required to import the point cloud via File > Import > Import Point Cloud and then specify that this point cloud to be used as laser scans data.
You can add several point clouds at the same time. Select all point clouds from the folder with laser scans data that you want to import.
In the Import Point Cloud dialog window specify parameters for import:
In case several point clouds were selected, the parameters will be applied to all point clouds that you want to import.
In the Import Points dialog window specify Direction (Generic, Origin, Trajectory file) and a value for Local surface neighbors for the following formats: ASTM E57 (*.e57), ASCII PTS (*.pts, *.pts.gz ), PTX (*.ptx).
If the point cloud was recorded in a structured form, then the Direction - Origin parameter should be used.
If the point cloud was obtained in an unstructured form, then use Direction - Generic.
In order to determine the normal of a point in a point cloud, Metashape approximates the local surface of the model with a plane.
The direction of the plane is determined by the nearby neighbors of a given point. The number of nearby points to consider is determined by Local surface neighbors parameter. If the cloud is very noisy, 28 default neighbors may not be enough to confidently determine the normals. For such point clouds, it is worth increasing the Local surface neighbors value to 100. Increasing the number of neighbors will slow down the calculation, smooth out the normals at the corners, but will help to avoid noise. In some cases, increasing the number of neighbors can help avoiding large inverted plots.
The imported laser scans data is displayed as point clouds in the Workspace pane and in the Model view:
In the Model view there are 2 Regions visible around the point cloud. The red color indicates the Point cloud Bounding box. The green color indicates general bounding box for this chunk. To disable bounding box for chunk: Select Model > Show/Hide Items > Show Region. To disable bounding box for point cloud: Left-click on the Workspace pane (for example, click on the name of the chunk) and the red bounding box will not be visible in the Model view. If you double-click on point cloud, it will appear again:
In Metashape available to change the color for bounding boxes. Select Tools > Preferences > Appearance tab:
To display the position of the scanner during shooting, you need to enable Show Cameras button on the Toolbar:
Select all laser scans on the Workspace pane and choose Use as Laser Scan from the Point Clouds context menu:
The point cloud and spherical panoramas with depth maps information (captured by the laser scanner) are also accessible on the Workspace pane:
For display only one point clod in the Model view select Set Active command from the laser scan context menu:
If a point cloud is assigned to be used as Laser scans, then it can be displayed in Model view by using Show Laser Scans data Toolbar button. Depending on the information recorded in the laser scan data, the cloud can be displayed as various modes: Solid View, Colors View, Classes View, Intensity View, Elevation View, Return View, Scan Angle View, Source ID View, Confidence View.
Processing only terrestrial laser scans
If laser scans were not aligned in third-party software before importing, then alignment can be performed in Metashape.
Before alignment, you need to disable the Lock Transform option in the context menu for all laser scans:
Select Workflow > Align Laser Scans command. In the Align Laser Scans dialog window specify the preferable parameters:
- Accuracy - at High accuracy setting the software works with the original distance between points, Medium setting causes downscaling by factor of 4, at Low accuracy source files are downscaled by factor of 16, and Lowest value means further downscaling by 4 times more. Highest accuracy setting upscales the distance between points by factor of 4.
- Reset current alignment - if this option is checked, all the key, and matching points will be discarded and the alignment procedure will be started from the very beginning. Uncheck this option to subalign some extra laser scans added to the chunk with already aligned set of laser scans.
- Key point limit - the number indicates upper limit of feature points on every laser scans to be taken into account during current processing stage. Using zero value allows Metashape to find as many key points as possible, but it may result in a big number of less reliable points.
- Vertical axis - set the vertical axis (X, Y or Z) of rotation of the laser scan.
WARNING! If the laser scans were imported into a project with aligned images, then when using Reset current alignment option in the Align Laser Scans dialog box alignment will also be reset for images.
Processing terrestrial laser scans and images
If you have aligned the laser scans in a third-party product before importing laser scans into Metashape, then you need to merge laser scans in one group and fix the group to preserve the alignment during the bundle adjustment step.
Select all laser scans on the Workspace pane and choose Move Laser Scans > New Laser Scan group. Then in the Group context menu select Set Group Type > Fixed:
Then add photos into project (select Workflow > Add Photos or Add Folder command).
You need to disable Lock Transform option for all laser scans and for group:
Select Workflow > Align Photos to align images with laser scans:
The result of the combined alignment of the laser scans and images will be displayed in the Model view:
Now the algorithm is implemented in such a way that you need to disable Lock transform to align with the images, and therefore laser scans can change the external orientation.
If you want that the laser scans not to change their position, then we can offer try to use markers as a workaround. In this case, you georeference images and laser scans to the same coordinate system. That this is not the alignment of laser scans and images together, you georeference the data using markers.
You need to create markers (3-5 markers) that will be used for georeferencing your data. You need to create this markers on the laser scans data (use Place Markers command from the context menu):
Specify markers on your images:
After you have placed all the markers on the point cloud click Update button on the Reference pane.
Also please note that markers are shown as white flags in Model view. If the position of a marker for each laser scan is specified, the flag becomes green. In all other cases (i.e. if the positions of the markers is only specified on the images) the flag remains white: