Mobile Mapping Tips and Tricks

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1 Mobile Mapping Tips and Tricks Using Ladybug Panoramas in TerraPhoto, April 2016 Introduction Traditionally, TerraPhoto has used individual camera images for point colouring for mobile mapping. For cameras such as the Ladybug, this approach has required that six individual cameras be setup and calibrated, which is both time consuming and potentially inaccurate (due to a difficult lens calibration). The use of a panoramic issue has the following benefits: Lens calibration no longer required resulting in higher accuracy Quicker to setup TerraPhoto s mission file and image list Better point colouring since there is no colour difference or vignetting between neighbouring cameras Pre-Requisites Software This guide has been developed and tested with the following software versions: Bentley Map v8i Select Series 3 TerraScan v TerraPhoto v MMProcess v Older versions may or may not work. 64 bit version of TerraPhoto do not support panoramic images at this current time (April 2016). User Experience The guide assumes the user has a basic knowledge of TerraPhoto for mobile mapping applications. Page 1 of 10

Note: it is not necessary to select a PGR file, since all events for all PGR streams will be processed. An image timing list called panoramic.001 will be created in the same folder as the PGR streams.

2 Step 1: Output panoramas and image timing file in MMProcess 1.1 Output Events Ensure the number of events matches the number of images in the PGR stream (Figure 1), and then click Add to Process Events. Note: it is not necessary to select a PGR file, since all events for all PGR streams will be processed. An image timing list called panoramic.001 will be created in the same folder as the PGR streams. 1.2 Output Panoramas Figure 1: Process Image Events Select the required PGR(s), and on the image options select the required colour processing method (High Quality Linear is recommended), and ensure Create Panoramic Images is selected. Click Add To Process Images. The panoramas will be created in a panoramas subfolder where the PGR streams are located. Figure 2: Process Panoramic Images Page 2 of 10

Roll and pitch will be approximately 0. Enter the lever arms for the centre of the camera. For the Ladybug3, use -860 for the approximate principal point Z.

3 Step 2: Setup TerraPhoto 2.1 Create a New Camera Calibration Create a new Ladybug3 camera calibration as shown in Figure 3. Figure 3: Camera Calibration Settings Enter the approximate heading of Camera 0. In this example, Camera 0 is pointing forwards and to the right by 72 degrees. Roll and pitch will be approximately 0. Enter the lever arms for the centre of the camera. For the Ladybug3, use -860 for the approximate principal point Z. Save the calibration file. 2.2 Setup a new TerraPhoto mission In TerraPhoto, click on Manage Camera Trajectories (Figure 4) and browse to the folder where the unthinned trajectory files are located. Figure 4: Manage Camera Trajectories Page 3 of 10

format is jpg and the image directory should point to the panoramas folder (Figure

4 Create a new TerraPhoto mission (Figure 5) and a new camera by clicking on Add. Figure 5: TerraPhoto Mission Numbering can be set to Last number in file name, format is jpg and the image directory should point to the panoramas folder (Figure 6). Figure 6: Mission Camera Save the TerraPhoto mission and close the camera dialog. Page 4 of 10

5 2.3 Create a New Image List Compute a new image list using the panoramic.001 image timing list (Figure 7). Save the image list. Figure 7: Compute Image List Please note: the create camera view tool will not work with panoramas. Page 5 of 10

and camera calibration dialog (Figure 8). 3.2 Add Known XYZ Points Figure 8: Tiepoints Windows Setup Turn on the mouse point adjustment tool, and set it up as shown in Figure 9.

6 Step 3: Define Tie Points 3.1 Setup the Tiepoints Windows Setup the tiepoints windows so that you can see the Active full, Active detail, Secondary detail, pointcloud top view, pointcloud cross-section view, tiepoints dialog and camera calibration dialog (Figure 8). 3.2 Add Known XYZ Points Figure 8: Tiepoints Windows Setup Turn on the mouse point adjustment tool, and set it up as shown in Figure 9. Figure 9: Mouse Point Adjustment From the tiepoints dialog, click on add known xyz and click on a ground feature such as a paint marking from the pointcloud top view. Click on the corresponding pixel from the active detail view, and then subsequently in the secondary detail view. Repeat for about 4-5 ground features, trying to cover the entire width of the panorama field of view. Turn the mouse point adjustment off, and draw a thin cross-section through a high vegetation feature such as a lamppost. Click on add known xyz and click on the feature. Click on the corresponding pixel from the active detail view, and then subsequently in the secondary detail view. Repeat for about 4-5 high vegetation features, trying to cover the entire width of the panorama field of view. 3.3 Solve Corrections Use Output Report from the Tie Points dialog to solve for heading, roll and pitch (Figure 10). From the resulting tie point report (Figure 11), click on the Apply misalignment button. Page 6 of 10

4 Add Air Tiepoints Compute depth maps for the panoramas and then add some air tiepoints.

7 . Figure 10: Optimal misalignment angles Figure 11: Tie point report From the Camera calibration dialog, click on solve parameters and solve for principal points xy and z. Click Apply and also save the calibration. 3.4 Add Air Tiepoints Compute depth maps for the panoramas and then add some air tiepoints. When you have full coverage solve for misalignment angles and principal points again. To check coverage click on Draw pixel distribution from the tiepoints dialog. Add more tiepoints if necessary. Close the tiepoints dialog when finished. Page 7 of 10

Click on Display, Fit Selected and click in a top view window. Note: if you have false eastings or northings you may need to temporarily reset these to 0 for this step. 4.

8 Step 4: Add Image Masks 4.1 Add Panorama Reference Open the Manage Raster References dialog. Attach one of the panorama jpg images (Figure 12). Figure 12: Manage Raster References Click on Edit, Modify Attachment. Click OK in the modify attachment dialog. This resets the position of the image. Click on Display, Fit Selected and click in a top view window. Note: if you have false eastings or northings you may need to temporarily reset these to 0 for this step. 4.2 Draw Masking Polygons Using the Smart Line tool, draw a polygon(s) around features to be excluded from the point colouring process, such as the GNSS antenna and the vehicle and sensor mount. Ensure that the black borders around the top and bottom of the panorama are also included inside the polygons (Figure 13). Select the polygons and from the camera calibration dialog click on Tools, Assign Bad Polygons. Figure 13: Bad Polygons Save the camera calibration, delete the polygons and detach the panorama reference. Restore any false eastings or northings if necessary. Page 8 of 10

9 Step 5: Colouring the Pointcloud 5.1 Extract Colour From Images From the TerraScan project dialog click on Extract Color From Images (Figure 14). Choose from one of the three Mobile colouring options. Ensure Use depth maps is ticked if you want to colour obscured objects accurately (such as buildings that are behind sign posts). Figure 14: Extract color from images Page 9 of 10

10 About the Author Dr. Christopher Cox has over 11 years' experience in the LiDAR industry. He was awarded a PhD in 2003 by the University of Nottingham for his thesis entitled ``The Use of Computer Graphics for Visual Impact Assessment``. Chris joined 3D Laser Mapping in 2005 and specialises in mobile mapping and airborne LiDAR research and development, as well as software support and training. Since joining the company, Chris has tested numerous MMS components, both hardware and software, from various suppliers from all over the world. Page 10 of 10

New Features in TerraScan. Version 013.xxx

New Features in TerraScan. Version 013.xxx New Features in TerraScan Terrasolid Workshop ILMF 2013 Denver, CO 14 February 2013 Darrick Wagg GeoCue Corporation 9668 Madison Blvd., Suite 202 Madison, AL 35758 +1 (256) 461-8289 support@geocue.com