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      Aligning SLAM Data to Ground Control Points in ROCK Desktop

      When processing SLAM data in ROCK Desktop you can align your data to Ground Control Points (GCPs) you have measured at the survey area.

      Tips for Successful Alignment

      • Understanding GCP Features: Before uploading control points, take time to explore your dataset in ROCK Desktop using the Intensity view to locate features used for GCPs accurately.
      • Projection Knowledge: Be sure of the UTM Zone and projection specifics for your ground control points to avoid alignment issues.
      • Iterative Process: Aligning to GCPs is often an iterative process. You may need to revisit and adjust control points multiple times.
      • Thorough Review: Don’t rush these steps. A careful review can save you from potential inaccuracies later on.
      • Keep Learning: For more on the importance of GCPs and how to maximize their effectiveness, check out GCP best Practices.

      Step-by-Step Guide to Align SLAM Data

       

      Aligning your SLAM Data to World

      1. Preparation:

        • Ensure your SLAM dataset has been fully processed up to step three in Rock Desktop.
        • Switch to Intensity View and adjust the range to identify the features that were used as GCPs.

      2. Uploading Control Points:

        • Click on the Align SLAM icon.
        • Select Insert Control Points and load your GCPs file. Ensure you choose the correct projection (e.g., WGS 84 UTM Zone XXN/S), and that your CSV is formatted correctly with columns for Title, XYZ, and Description.
        • Review the GCP information you have uploaded.

      3. Adding Alignment Points:

        • Use the Add Alignment Points option.
        • For each control point:
          • Identify the feature in the dataset corresponding to your GCP.
          • Select the correct control point number (e.g., control point 1, control point 2, etc.) from the drop down.
          • Click on the corresponding point for your GCP location.
          • Fine-tune the placement using the drag-and-drop feature if necessary.
      4. Aligning to World Coordinates:
        • After setting a minimum of three control points, click Align to World.
        • The alignment process will vary in duration based on dataset size and complexity.
        • Once completed, the data will be aligned to the specified GCPs.

      Aligning your SLAM Data to Control

      1. Adjusting the Intensity View:
        • Re-enter Intensity View and adjust the range as needed to clearly visualize the GCP features in your dataset.
      2. Adding and Fine-Tuning Alignment Points:
        • After aligning your SLAM data to World, you can align other control points in your dataset.  
        • Using Intensity view you can inspect the placement of the other GCPs relative to the corresponding features at the site.  
        • If the initial alignment isn't perfect, adjust the alignment by selecting and repositioning the control points. This step ensures your data aligns perfectly with the easting, northing, and Z values of your GCPs.
        • Use the Add Alignment Points option.
        • Identify the feature in the dataset corresponding to your GCP.
        • Select the correct control point number (e.g., control point 1, control point 2, etc.).
        • Fine-tune the placement using the drag-and-drop feature as necessary.
      3. Inspect and Adjust:
        • Review all control points (e.g., Point 37, Point 38, etc.) and make any necessary adjustments by adding or moving points to match the precise locations in your dataset.
        • Continue this process for all points, such as Points 36, 35, 34, etc. ensuring each is correctly aligned.
      4. Final Alignment:
        • After setting at least five control points, click Start Alignment.
        • ROCK Desktop will process the alignment based on the selected control points, refining the overall alignment of your dataset.
        • The alignment process will vary in duration based on dataset size and complexity.


      Validating Your SLAM Data Alignment

      1. Reviewing the Alignment:

        • Make sure you are using Intensity view to get a clear look at your data. Adjust the range as necessary to bring out the features you want to focus on.
        • Carefully inspect each control point that you aligned earlier.
        • Verify that each point (e.g., Point 1, Point 2, etc.) is correctly placed in the XYZ coordinates.

      2. Adjust and Redo if Necessary:

        • Depending on the number of GCPs used, it’s possible that not everything will align perfectly on the first try. If you notice discrepancies, take the time to adjust the control points accordingly.

      3. Finalize the Alignment:

        • Once you’re satisfied with the alignment, click Next to proceed with the remaining processing steps.
        • This will confirm that your points are accurately positioned in the real-world XYZ space, based on the GCPs you imported.

      If you have any other questions or comments about this workflow please contact ROCK Support (support@rockrobotic.com).