The Q-Points tool is a unique algorithm that intelligently converts your drone elevation data into discrete points that best model your topography. This allows you to quickly create very detailed surveys over bare-earth environments with minimal work.
Q-Points are a function of the Point Grid tools within the HOME tab of Virtual Surveyor. Q-Points are used to generate topography points that can be used in your surveys and Surface (TIN / Contour) creation. When using the Q-Points tool the resulting output will be a Multi-point item that contains all of the generated Q-Points that model your Elevation Terrain.
Q-Points work differently than your typical grid points (Rectangular / Triangular). Most Point Grid tools place points at set distances in a set pattern (such as a Rectangular pattern with 25ft or 8m between points). Q-Points on the other hand are points modelling your terrain and it's elevation shifts by placing points only at locations of elevation change.
Rather than inputting a Grid Size, Q-Points require an Elasticity value. The Elasticity value represents the vertical shift required for a point to be generated. When computing where to place points, the Q-Points tool will model a generalized surface on your Elevation Terrain and then checks for inconsistencies where the modeled terrain and Elevation Terrain differ. If the inconsistency is greater than your input Elasticity value, in either a positive or negative Z shift, a point will be placed at that location.
Quick Usage Guide
- Create a Boundary around the area you wish to run Q-Points and select it.
- Within the HOME tab, Navigate to the Point Grid section and choose Q-Points in Type.
- Set an Elasticity parameter.
- Click on the Point Grid button to start generating Q-Points.
- A progress bar in the bottom left of the software is displayed and points are created in the Viewport.
- Q-Points are created as a Multi-point item in the Project View.
How Q-Points Work
- Select the boundary you wish to run Q-Points in. Your boundary(s) should cover the desired area for the survey, and can be simple, complex, or broken into multiple areas to only run Q-Points where appropriate. When selecting more than one boundary, Q-Points are run in each boundary consecutively.
- Select the Q-Points type in the Point Grid tools area and set the Elasticity. The Elasticity drives the precision of your Q-Points survey by setting a threshold at which a point is placed when an elevation shift larger than your Elasticity is detected. The image above compares points created at an Elasticity of 1ft and 2ft. Notice the flat areas have little to no points as they did not exceed the Elasticity, while areas of rapid elevation change—the walls and slopes—have many points.
- The lower the Elasticity value, the more points you end up creating; the Q-Points tool is looking for smaller differences of change between the computed model and the drone data. However, it is not always best to set low Elasticity values as you might create more points than necessary to accurately survey your site. Creating more points than necessary will slow your process down, as you need to generate, clean, and then export your points. You might also create too many points to export into your CAD program. Compare the 2ft contours generated from the 1ft and 2ft Elasticity values from before. Even with different values the contours turn out similar with half the data to export.
- The Q-Points tool is best used on bare earth, or areas with limited surface items. The tool does not recognize the difference between ground and surface features, such as the image above where you can see points grouped on top of the construction equipment. You need to clean or remove these points from the surface features when using Q-Points.
- As shown in the images above, Q-Points is generally not the best Point Grid tool to use in complex environments that include a lot of surface features; complex environments include urban or highly vegetated areas. You can generally use a combination of other Point Grid tools such as Low-pass or Rectangular with much less effort than the Q-Points tool for complex environments.
Most Common Uses for Q-Points
- Q-Points are best used for surveying and topographical (TIN / Contour) modeling over bare earth environments (mines, construction sites, etc.).
Tips and Tricks
- Q-Points work best in open landscapes, or sites with mostly bare earth. Avoid using Q-Points in highly vegetated areas, urban areas, or other environments with complex surface features.
- Remember, you can always use any Point Grid tool over small subsets of your whole project. If you have areas where Q-Points would work best, use them there, and other Point Grid types in the other areas where it may not be suitable.
- Use the Area Select tool after running Q-Points to remove groups of unwanted Q-Points instead of deleting them individually.