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 are unique to Virtual Surveyor and 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 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 then select it
- Within the Home tab Navigate to the Point Grid section and choose Q-Points in Type
- Set a Elasticity parameter
- Click on the Point Grid button to start generating Q-Points
- A progress bar in the bottom left of the software will display, and points will be created in the Viewport
- Points will created in a Multi-point item
How it works
- 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 will be 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 will be placed when an elevation shift larger than your Elasticity is detected. The image above compares points created at Elasticity of 1ft and 2ft. Notice flat areas have little to no points (they did not exceed the Elasticity), while areas of rapid elevation change (walls and slopes) have many points
- The lower the Elasticity value the more points you will end up creating (as the tool will be looking for smaller differences of change between the computed model and the drone data). However, it is not always best to set very low Elasticity values as you can create more points than needed to accurately survey your site. Creating more points will slow your process down as you need to generate, clean, and then export them. You also may create such a large amount your model won't 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 on the whole.
- Q-Points 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 will need to clean or remove these points or features if using Q-Points.
- Q-Points is generally not the best Point Grid tool to be used in complex environments that include a lot of surface features. These environments include urban, or high vegetated areas such as above. You can generally use a combination of other Point Grid tools such as Low-pass or Rectangular with less effort than the Q-Points tool for these environments.
Most common uses
- Surveying and topographical (TIN / Contour) modelling 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 high vegetation areas, urban areas, or other environments with many surface features.
- If there are surface items such as vehicles, construction equipment, or other temporary features you can remove them before running the Q-Points tool using the Clean Terrain tool so Q-Points are not generated on them.
- 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.