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Build a Project with Drone Data

Ayelet Rabinowitz
  • Updated

This tutorial outlines the complete workflow for creating professional grade 3D output in PhotoMesh using drone data, from loading your photos into PhotoMesh to generating 3DML output:

Data Included in Training Folder (Airwise_Sample_Drone_Data)

This project’s photos and and everything else you need to create your mesh is included in the Airwise_Sample_Drone_Data folder:

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  • Nadir_Oblique_Images folder that has two subfolders:
    • 45 folder, containing 141 jpg files. These are the oblique images.
    • 90 folder, containing 144 jpg files. These are the nadir images.
  • Tie_Point_Demo folder that contains:
    • Drone_Training_cp.gcp (text format) file with ground control point data.

Download project data

Step 1: Starting a New PhotoMesh Project

Do the following:

  1. Click Start > Skyline PhotoMesh > PhotoMesh.
  2. Click the PhotoMesh button , and then click New (CTRL+N). The New Project dialog box is displayed.
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  3. Enter a name and path location for your project.

Step 2: Loading the Project Photos and Setting AT/Reconstruction Areas

Photos can be loaded into a project using several different methods. In this tutorial, we will be loading a folder of photos. More about: Loading Photos into a Project >

  1. On the PhotoMesh Home tab, from the Photos dropdown menu, select Load Folder. Then browse to .\Airwise_Sample_Drone_Data\Nadir_Oblique_Images, and click Select Folder. This folder includes two subfolders: ‘45’ and ‘90’. A dialog box is displayed asking whether you want to create a separate collection for each folder. Click Yes.
  2. Modify the photos' coordinate system: In the Project Tree, select the two photo collections, and then in their properties sheet, click the three dots next to the current coordinate system. The Coordinate System dialog box is displayed.
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  3. Search for "4326", and then select WGS 84 as the new coordinate system, and click OK.drone3.png
  4. Set the reconstruction area to the same as the AT area: On the Home tab, in the Area group, from the Reconstruction Area drop-down menu, select Same as AT Area.
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Step 3: Using Tie Points to Improve AT Results

PhotoMesh provides three types of control points for improving your AT results: ground control points, check points, and tie points. In this training exercise, we will be working with tie points. Tie points establish a correspondence between project photos and improve aerotriangulation through identification of the same physical point in three or more photos. Generally, it is recommended to run an initial aerotriangulation to identify photos that either weren’t calculated in AT or that have high median errors, as well as areas of insufficient matches between groups of photos.

Control points can be created in PhotoMesh or imported in a GCP (text format) file with control point information. More about: Control points >

In this tutorial, you will be importing a GCP file which includes the locations on the terrain in which control points were created and the pixel coordinates of the marked control point in each sampled photo.

To import tie point data:

  • On the Home tab, click the arrow under Control Points and select Import. Then in the Import Control Point File dialog, browse to .\Airwise_Sample_Drone_Data\Tie_Point_Demo\Drone_Training_cp.gcp in your training packet, and click Open.

Step 4: Performing an AT Only Build

For optimal AT results, it is recommended to initially perform only the aerotriangulation step (“AT Only”), and then review the results, to ensure a precise AT which includes all project’s photos that intersect with the AT area, before proceeding with the rest of the build. If the results of the AT Only were in fact satisfactory, you can continue with the rest of the build process.

If the results of the initial AT Only build were unsatisfactory, AT parameters or collection properties should be modified and/or control points added/edited based on the aerotriangulation result. More about: Evaluating and Improving Your AT > Then the aerotriangulation should be repeated by selecting AT Only, and your results reviewed. When repeating the aerotriangulation, PhotoMesh determines precisely which tiles and which specific AT sub-processes were affected by the modification of properties or control points, enabling a much lighter and faster AT process. This iterative process should be repeated until satisfactory AT results are achieved.

To perform an AT only build:

  1. On the Home tab, in the Build group, click Build. The Build Parameters dialog box is displayed.
    drone5.png
  2. On the Steps tab, select AT Only. Then click Select and Manage Presets. The Preset Manager is displayed.drone6.png
  3. On the Select Presets tab, clear the Selected Presets list on the right side of the Preset Manager by selecting each preset and clicking Remove . On the left side of the Preset Manager is a list of available presets. Select the AT: Unreliable orientation preset from the Available Presets list, and click Add to move it to the Selected Presets Then click OK. This preset provides a more robust calculation of positioning and orientation information and camera parameters, which is critical for drone data collected using only standard GPS.  
  4. In the Build Parameters dialog, on the AT tab, note the settings that are defined by default for performing aerotriangulation. Click Build to start the build. The New build description dialog box is displayed.
  5. Enter a build name and click Ok. The PhotoMesh Build Manager is displayed.
  6. Select the required fusers (see Step 5), and click Build.
  7.  

Step 5: Starting and Managing Fusers

PhotoMesh fusers are the worker components of PhotoMesh, which allow you to share the demanding processing requirements of the different build steps (photo preparation, AT, point cloud, mesh model, texture, 3DML/other outputs) between several computers on the same network. When beginning the build process, the PhotoMesh Build Manager application determines what build steps are required and assigns them to the different fusers. PhotoMesh Build Manager and PhotoMesh fusers use the working folder to communicate: to deposit and collect pending tasks, and share information about fuser availability, status and progress. Before beginning the build process, you should start the fusers that will be participating in the build, and set their working folder. More about: Working with Fusers >

Step 6: Performing a Complete Build

After satisfactory AT results are achieved in an AT Only build, you are ready to perform the full build process and generate your required outputs.

To build your project:

  1. On the Home tab, in the Build group, click Build. The Build Parameters dialog box is displayed.
  2. On the Steps tab, click Complete Project. This sets the project to resume building from the current step until completing the generation of the selected outputs.
  3. Click the Reconstruction tab to configure the reconstruction parameters. Most of the required reconstruction parameters were already defined based on the preset selected in Step 4. The only parameter that requires modification is Point Cloud Quality. Set the Point Cloud Quality option to Low 1/4 resolution. This should provide a good balance between performance and quality. If you only have one or two fusers, running the project in 1/4 resolution can take 50-60% less time than with 1/2 resolution since fewer tiles will be generated. More about: Setting Build Parameters >
    drone7.png
  4. On the Output tab of the Build Parameters dialog, select the check boxes of the required outputs. For the purposes of this tutorial, select the 3DML.
    drone8.png
  5. Click Build. See Step 5 for information on starting and managing fusers.
  6. When the build is complete, it will be listed in the Project Tree. Check its box to display the final output.
    Note:  To open the project in TerraExplorer, right-click the build folder in the Project Tree and select Open with TerraExplorer.

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