Drone data usually comes with noisy water surfaces. Photogrammetric processes do not work well over liquid surfaces and cannot deliver relevant Digital Surface Models (DSMs) in those areas. To get a surveying grade result, the noisy part of the Elevation Terrain needs to be flattened. 


Here is a quick guide to get rid of this noise in a few steps and enhance your map quality with Virtual Surveyor.


Overview


Draw the Water Body Boundary

The first step is defining the water surface extent. To easily draw a line around it you can use the Extract Level tool available in the HOME tab. 

  1. Click on the Extract Level button to activate the tool.
  2. Click a point on the bank that intersects the water level and the terrain. 


If it's difficult to determine the intersection point between the water level and the terrain, you can use the Water tool available in the TOOLS tab for Boundary. 

  1. Draw a rough boundary around the pond, select it and click on Water. 
  2. Select the water item and adjust it to the actual water level. 
  3. Click on Intersect Terrain to generate the water body boundary. 
  4. Erase all the polylines except the outer boundary.


Clean the Water Boundary

Sometimes it's necessary to locally adjust the water extent limit. Due to the noisy surface or objects on that surface, it is possible that the boundary doesn't follow the bank in certain place.


  1. Use the Edit Vertex tool available in the TOOLS for Boundarytab to adjust the vertices position.
    1. You also need to select XY in the Edit Vertex Mode box.
  2. You can also delete large section of the boundary thanks to the range selection (press Shift + click first and last vertex of the range). 


You may also split the boundary and create a new section manually with the Polyline tool. 

  1. Make sure that all the new vertices are on the same elevation as the main boundary. 
  2. After creating the new section, click on Edit Vertex in the TOOLS for Boundary tab to adjust their elevation.
    1. Click Select All Vertices (Ctrl+A) to edit all vertices simultaneously.
    2. Select Z in the Edit Vertex Mode box.

  3. Pay close attention to the fist and/or last point(s) of the new section, it has to be located at the exact same position as the splitting point of the water boundary. 
  4. Select both polylines and merge them.


Triangulate the Water Boundary (Create the Surface) 

  1. Select the water extent boundary and Triangulate Within to create the plane water surface.


Modify the Terrain to Remove Noise  

  1. Select the water surface item and, in the TOOLS tab, click on Modify Terrain to remove the noise and make a flat area within the pond boundary.