Working with Point Clouds - Merge Workflow

Contents

• Introduction
• Step 1: Configure your merge job
• Step 2: Review and manually align your datasets
• Step 3: Start processing
• Step 4: View your final output
• Step 5: Combine your datasets
• Step 6: Colorize your Merged Point Cloud (Optional)

Introduction

The primary purpose of the Merge workflow is to align multiple point cloud datasets together so that they share a common coordinate system, which is useful for change detection or correcting the edges of your datasets (where Hovermap’s accuracy naturally drops off). This function ensures that the points from different datasets are correctly positioned relative to each other.

You need to include a reasonable amount of overlap between scans to provide sufficient information for alignment. The exact amount of overlap varies, depending on the environment and individual dataset trajectories. However, a rough guide is to have one-third of each dataset overlap with the next.

Step 1: Configure your merge job

1. Open Emesent Aura. Make sure you have an active SLAM license.

2. In the Process tab, click Process Scan.

3. In the Configure New Scan Job panel, select the Merge workflow.

4. Click Add Datasets.

5. In the dialog box that displays, click Add then select the point clouds you want to merge. Make sure all the point clouds have been pre-processed in Aura.
   Note: There is no strict limit to the number of files you can merge. You can work out your limit based on the size of your point cloud files and your RAM. Avoid merging point cloud files that add up to more than the sum of your RAM. You should also account for the amount of RAM your system requires to run.

6. In the Alignment Preview File column, select the scan file to use for alignment.
   Tip: Merging is done on the full point cloud regardless of the selected Alignment Preview File. To make the alignment process more practical, it is recommended to use only the subsampled files to lower the computational resources needed, especially for large datasets. In addition, the reduced set of points on a subsampled file allows you to focus on key features or points of interest, which can facilitate more accurate alignment, leading to higher-quality merged point clouds.

7. Select the reference scan file. The reference scan file provides a fixed frame of reference for aligning the other point clouds. Selecting a reference scan establishes a coordinate system that other scans can be transformed into, ensuring proper alignment between them. A target icon beside the point cloud file in the Visualize tab indicates a referenced scan file.

8. Once you have added all the point clouds to merge, click Save.

9. In the Location field, enter the preferred name for the output folder. Also, select the location where this folder will be created.

10. Choose your merge profile. Go to the Processing Profile section in the Emesent Aura user manual for more information on the available profiles.

Step 2: Review and manually align your datasets

To manually align your point clouds:

1. Click Load Scans to start your review. All scans will load at the same time.
   Note: To add or remove a dataset from the current merging job, click Edit Point Clouds Selected.

2. Set a unique color for each point cloud so you can easily differentiate and identify individual point clouds in the merged dataset. To do this, select your point cloud in the Visualize tab then go to the Context panel. Under Color Scale, select Solid from the dropdown list. In the Fill color section that appears, select a color from the color palette or choose a custom color by specifying the RGB or Hex values.

3. Once you have set the colors for all point clouds, go back to the Visualize tab then select your point clouds. Press Shift to select more than one point cloud.

   1. In the Main Toolbar, set the view to Top then go back to the Visualize tab and select only your second point cloud.

   2. In the Main Toolbar, use the Translate tool to drag the second point cloud and align it with your reference point cloud on a common point.

   3. In the Main Toolbar, use the Rotate tool to further improve the alignment. Repeat as necessary to achieve a reasonable alignment when viewed from above.

   4. Select all your point clouds again then go to the Main Toolbar and set the view to Front.

   5. In the Main Toolbar, use the Translate tool to drag your second point cloud up or down to align it with your reference point cloud.

Click Start to begin processing. The Configure New Scan Job panel is replaced with the Processing Scan panel and shows a progress bar showing how far along you are in your processing job. In addition to the progress bar, the elapsed time of the processing job is shown to the right.
The directory file path below the progress bar provides a way to identify the dataset source. This is useful if simultaneously processing multiple jobs with the same output folder name. Copying the file path and pasting it on your computer’s file explorer allows you to access the completed files without having to wait for the processing job to be completed.

Step 4: View your final output

1. Once processing has been successfully completed, you will get a Merge complete notification. Click Open folder to view the output folder or View to display your merged point cloud in the Viewport. 

2. Once loaded into the Viewport, you can then interact with your merged point cloud.

3. Click Close to remove the scan information from the processing space.

Step 5: Combine your datasets

1. Click View for each dataset you want to combine to load them in the Point Clouds section of the Visualize tab.

2. Hold down the Shift key then select the datasets you wish to combine.

3. Once selected, click the Project Menu icon then select Save As.

From Emesent Aura version 1.5 or later, it is possible to colorize a merged point cloud.