Waterbody enhancement using shape files
Strong reflections and changing appearance due its moving surface prohibit the accurate reconstruction of waterbodies from images employing stereo vision methods.
In order to acquire highest quality True Orthos and Meshes, SURE software provides the possibility to crop & replace sparse and noisy data generated on water bodies with smooth data interpolated from 3D polygons. These 3D polygons can be specified in terms of shape files (e.g. along coastlines, lakes, rivers, etc.), where each polygon vertex also has an attached height value (z coordinate). During the DSM's interpolation stage and/or Cloud Filter processes the specified polygons will be applied to either the raw DSM's or the raw Dense Clouds on-the-fly, leading to enhanced 2.5D and 3D surface models. Note that the raw DSM's and dense clouds themselves will remain unaltered by this process.
Follow these easy steps to enhance your surface models by applying water body polygons:
Step 1 - digitize waterbody polygons
In case shape files containing 3D polygons in the required format are already existing you can skip this step and directly move on to step 2. Otherwise, in order to digitize the 3D polygons, use any available data source, e.g.
- digital terrain models (DTM)
- LiDAR data
- DSM or True Ortho data from previous projects
and capture the polygons along coastlines, lakes, and river shores using your preferred GIS.
If no data is available in order to digitize the polygons, proceed as following
- Setup your project with SURE as usual, disregarding the waterbody polygons. See also this article for further information.
- Process your project up until the DSM stage is finished.
- Use the produced DSMs (32 Bit TIFFs, representing height) or optional Orthos (colorized TIFFs) in order to digitize the required waterbody polygons. Additional QA layers which can optionally be produced by SURE can be beneficial for the digitizing process, for example the binary mask.
- Continue with step 2 and use either the 2.5D Tool or the command line Modules to generate the enhanced surface models and True Orthos
Shape file coordinate system
Single shape file
You can only specify one shape file (.shp) that contains all relevant polygons for your entire project. This shape file, however, can contain multiple polygons within a single layer.
Digitizing waterbody polygons with QGIS (3D Polygons supported since QGIS v3)
Step 2 - apply waterbody polygons
Either you already processed the dense clouds in the previous step 1 or you're setting up the project from scratch, you can use both the graphical user interface (GUI) or the command line interface (CLI) to apply the waterbody polygons defined in a shape file.
During the 2.5D workflow (DSM, True Ortho, DSM Mesh), the waterbody polygons will be applied to the raw DSM's on-the-fly, so the raw DSM's themselves will remain unaltered by this process. These outputs within the DSM subfolder will not be affected:
When processing 3D workflows, the waterbody polygons will be applied to the raw dense clouds on-the-fly. The raw dense clouds themselves will not be affected: