Working with Point Clouds - Reproject your Point Cloud

Reprojection in Emesent Aura is an automated workflow that allows for RTK scans to be processed with the correct coordinates by simply selecting the target coordinate reference system (horizontal) and converting from ellipsoidal height to orthometric height using a GEOID model (vertical). This can be done via Processing Settings when processing raw data or Export reprojection from the Project menu if exporting a georeferenced point cloud.

The following video shows how to use Emesent Aura to easily reproject your raw RTK scan during processing and reproject your older scan during export.

Processing and Reprojecting Raw Point Cloud Data

1. Open Emesent Aura and in the Process tab, click Process Scan.

2. In the Configure New Scan Job panel, select the Process workflow.

3. Click Add Dataset then browse for the folder that contains the raw RTK data to be processed. Select that folder.

4. You will be prompted once RTK data is detected in your dataset. Toggle on Use RTK data.
   

   

5. In the Location field, enter the preferred name for the output folder. A subfolder is created, which stores all the processed results and data.

6. Click Processing Settings. Under Georeferencing in the General tab, select the RTK device and GNSS receiver used to capture the RTK data.
   
   
   NOTE: For optimal results, ensure that the Georeferencing mode and GNSS receiver type match the hardware used during data collection. While the resulting point cloud remains usable, the accuracy may be affected.

7. Under Base coordinate reference system, set the Coordinate Reference System in which the data was originally collected. This information is essential for accurate transformations and reprojections to the target CRS.
   
   
   Alternatively, toggle on Custom base coordinate reference system to enter a project string that describes the desired geodetic coordinate reference system.
   
   
   

8. Toggle on Reprojection then select the appropriate Horizontal and Vertical coordinate reference systems.
   Horizontal: Reproject to a different map projection or coordinate system.
   Vertical: Convert from ellipsoidal height to orthometric height using a GEOID model.
   
   
   Alternatively, toggle on Custom target coordinate reference system to enter a project string that describes the desired target coordinate reference system.
   
   
   

9. Click Save.

Reprojecting a Processed Point Cloud

1. Open Emesent Aura and go to the Visualize tab.

2. Load the processed point cloud or trajectory you want to reproject.
   
   

3. Click the Project menu icon then select Export projection.
   
   

4. In the Export Reprojection dialog box, click Edit Source CRS. This step is optional as Emesent Aura automatically detects the CRS of the input data. However, editing may be necessary if the CRS is incorrect or you are working with data from multiple sources that require a specific CRS.
   
   
   Refer to the Context Panel on the right of the screen to see the projection information of the current point cloud.
   
   

5. Select the target Horizontal and Vertical coordinate reference systems or toggle on Custom target coordinate reference system to enter a project string that describes the target CRS.

6. Enable Reproject trajectory to apply reprojection to the trajectory data associated with the point cloud, ensuring that any movement or path data is aligned with the target CRS.

7. Enable Replaced loaded point cloud with exported reprojection to replace the currently loaded point cloud with the newly reprojected version.
   
   

8. Click Save. The results are saved in the same output folder as the original point cloud.

Frequently Asked Questions

Why are there two trajectories in the Output folder when reprojecting as part of the processing workflow?

Two trajectories are provided in the output for different purposes:

• The SLAM projection trajectory is necessary for accurate colorization. It will be automatically selected when colorizing a reprojected dataset. The colorized output will maintain the target CRS that was applied to the selected SLAM output folder for colorization.

• The user's Target projection trajectory (with “_projected” suffix) is needed for the following purposes:

  • Viewing the trajectory alongside the reprojected point cloud in the same CRS.

  • Extracting 360 images, which are also reprojected to a target CRS.

How can I colorize a reprojected point cloud?

Ensure the RTK dataset is processed with reprojection before colorizing it as usual. The colorization process will use the default SLAM projection trajectory to ensure accurate results. The point cloud output after colorization will be in the user's Target projection.

How do I extract 360 images from a reprojected point cloud?

To use 360 Image Extract, the trajectory in the Output folder should have the default naming convention (e.g, scan_folder_name_traj.xyz).

To use a reprojected trajectory, rename the reprojected TRAJ and PRJ files in the Output folder to the default naming convention. For example:

Also, rename the original TRAJ and PRJ files. For example:

Once the filenames have been renamed, run 360 Image Extract as normal.

My point cloud was reprojected into a target horizontal CRS using a previous version of Emesent Aura (1.7 or earlier). Is it possible to only reproject it into a target vertical CRS to apply a GEOID to my data?

Yes, load the point cloud or trajectory in Emesent Aura then perform the following:

1. Select Export reprojection from the Projects menu.

2. Keep the source horizontal CRS as is and leave the vertical CRS blank.

3. Use the source horizontal CRS as the target CRS and specify a vertical CRS to apply the GEOID.