Virtual surveyor includes tools to properly map curbs and gutters from drone data. In general, photogrammetry results have limitations when looking at the top edges of curbs. Image processing solutions can not generate very sharp edges. This step by step guide will allow you to get an accurate model of curbs and gutters and export it as a regular CAD file. Those items can also be used to modify the elevation terrain and go further in your project analysis.
- Survey the back of the curb from the drone data.
- Create offset polylines.
- Triangulate the polylines to create the curb and gutter model.
- Export the model as a CAD file.
Survey the back of the curb
The 2D mode is the preferred view mode to survey the back of the curb. Use the Polyline tool available in the HOME tab. If the curb is curved, switch the line drawing mode to Arc to carry on with the survey. You can use the Edit Vertex tool to add vertex or adjust existing ones when the curb is irregular.
Densify the polyline to make sure that it captures enough topographic detail from the elevation terrain. Use the regular densify method. Switch back to the 3D view mode to check the polyline.
Offset the back of the curb
The other curb and gutter lines are parallel to the back of the curb. Select the back of the curb polyline and use the Offset Line tool available in the TOOLS Tab. Here you need a field observation to determine the height of the curb.
Offset the line with ΔZ = 0 to draw the width of the curve.
Offset the line with ΔZ = - height of the curb to draw the flowline. In general, you can easily locate this line as it correspond to the darkest part of the item.
Offset the line on terrain to draw the width of the gutter.
Create the curb and gutter model
Select the curb and gutter polylines and Triangulate.
Export CAD file
When the whole project has been model, export it as a CAD file. You can then use the data in a engineering or CAD design software.
Tips and tricks
- Cars or other obstacles can obscure the curb in places. To properly model the curb, Edit Vertex with Interpolate Z settings. It will smooth the polyline under those obstacles. Remember to do that for each line.
- Integrate the curb and gutter model into your drone data. Select the curb and gutter surface item and click Modify Terrain. The TIN surface now contains sharp edges and water flow can be correctly modeled.
- Some TIN segments may need to be removed. Use the Remove Triangles tool available in the TOOLS tab to clean the curb and gutter model.