Editing DSM True Ortho and DSM Meshes using 3D shapefiles (Beta)

General Concept

SURE contains the 3D shapefile functionality, nominally designed for interpolating the waterbody surfaces. This function can be used to improve the quality of the DSM, the True Ortho and the DSM Mesh in areas that suffer from defects.

Shapefiles used for this workflow must contain 3D Polygons (in a single layer). These polygons are applied during the DSM step and the interior of the polygons will be interpolated according to the Z values of the polygons' vertices.

Applications

The DSM and subsequently the True Ortho or DSM Mesh may suffer from imperfections due to shortcomings in the input data, or in the settings, or algorithm employed (e.g. : insufficient coverage leading to stereo occlusions determining data gaps, noise around building edges / thin structures, noise in road traffic areas, etc.)

The shapefile-based editing workflow opens the possibility of correcting artifacts in the native DSM product:

  • Interpolating arbitrarily large NO DATA areas

  • Straightening and sharpening building edges

  • Flattening ground / roof areas that suffer from high frequency noise (e.g. over-exposed or reflective surfaces)

Example of DSM/True Ortho before / after editing:

Workflow

SURE Editor

SURE Editor is the specialized tool for implementing the shapefile-based editing workflow. It provides an interactive environment for digitizing 3D polygons and enables the reprocessing of the edited tiles with the appropriate settings.

The digitization process takes place on the untextured DSM Mesh.

Step-by-step guide

  1. Start the SUREEditor.exe (in the SURE installation folder)

  2. Load the SURE Project subject to editing: Drag-and-drop the Project.spr file into the SURE Editor interface. This will load the camera stations in the viewer.

  3. Load the untextured DSM Mesh results from Project_folder/Results/DSM_Mesh_Untextured/osgb: Drag-and-drop the DSM_Mesh_Untextured.osgb into the SURE Editor interface. (Press ‘T' and ‘L’ keys to toggle the mesh to ‘shaded' viewing mode)

  4. Enable the Edit mode

  5. Digitize the 3D polygons to repair artifacts in the DSM, True Ortho and/or DSM Mesh. See Editing Tools below, for more details.

  6. Reprocessing with the 2.5D Tool: after finishing the editing process, press “Ctrl+B” to launch the 2.5D tool. When you have valid correction polygons, the corresponding settings will automatically be filled in. The 2.5D tool will only reprocess the tiles that are affected by the edits.

Editing Tools

Shape Digitization tool

  • Press "1" to activate.

  • Ctrl+Left Click for adding new vertices.

  • Ctrl+Right click to accept the polygon.

  • Esc to cancel the creation of the current polygon.

  • Ctrl+S or Editor menu → Save polygons to shapefile to export the polygon to a shapefile.

  • Ctrl+Q or Editor menu → Clear all polygons: clears all polygons in the current Editor session (does not delete previously saved polygons into shapefiles on disk).

  • Shapefiles containing 3D polygons can be imported by drag-and-dropping the file into the viewer, while being in the Edit mode.

Saving a shapefile will create a new subfolder in your base project with a timecode (e.g. CorrectionShape-19-09-27-14-10-53). This includes a "DigitizedPolygons.shp" file that contains the polygons and an "EditedAreaShape.shp" file that can be used as an area shape when reprocessing DSMs/TrueOrthos. The latter contains all tiles that are affected by the polygons and should be used as area shape file for reprocessing the DSM in conjunction with the original min/max values of the bounding box.

Guiding Plane tool

This tool allows drawing a polygon with a height that differs from the current mesh. This is especially useful if a building's rooftop does not extend enough in the True Ortho and appears to be eaten out. The plane is manually defined by specifying 3 points on the DSM Mesh.

  • Press “2” to activate

  • Ctrl+Left Click for adding a plane defining point. Setting the third point will generate a plane.

  • Ctrl+Scroll Wheel for scaling the extent of the plane.

  • Esc for clearing the plane.

  • Ctrl+A toggles the state of the plane: active / inactive.

Initially, the plane will be transparent, which means that it is inactive. After Ctrl+A, the plane will be visible while the mesh turns transparent, which means that the plane is active.

If the mesh is active, the Shape Digitization tool will sample the vertices of the polygons on the mesh, i.e. using the meshes height as z-value. If the Guiding Plane is active, the Shape Digitization tool will sample points on the plane, i.e. using the plane's height as z-value. You can freely toggle the plane's state while digitizing, resulting in some points being sampled on the mesh and others on the plane.

New viewer features

Input image overlay

  • Pressing "C" will open the image that is closest to the point in the center of the screen. It is overlaid to the mesh so that you can spot differences and digitize roof edges.

  • Pressing "L" toggles the shading mode and can help to concentrate on the image. The perspective can not be changed by rotation as we are bound by the projection of the input image. You can however pan around using a right-click and moving the mouse. Clicking right and left arrow allows showing more images observing the same scene. The image overlay is turned off by pressing "C" again.

True Ortho Overlay

  • Pressing "O" will open the True Ortho photo covering the point in the center of the screen. The behaviour is the same as with the input image overlay. This view can be closed by "O" or "C". It is currently required that the True Ortho tiles are situated in the Results/True_Ortho/ folder relative to the Project Directory.

Field of view

  • Shift + Scroll Wheel (down): Change the viewer's field of view up to a pseudo-orthographic projection. Ortho view is especially helpful when clicking the "Fix vertical camera axis" checkbox and rotating the camera to a vertical view (such that the camera axis is pointing into Nadir direction).

Height color texture mode

  • Press "T" to cycle different texture modes (real texture if available, height and uniform color). Can be combined with shading (press "L" to cycle shading modes). This also works with the image overlay being active. The color range can be adapted using the slider in the upper right corner. Similar for the Brightness.

Align Mesh to North

  • Pressing "N" aligns the mesh to north for easier comparison of the current view with GIS software.