Grid of points - PIX4Dsurvey

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Pix4Dsurvey distant outlier filter icon

Outlier Filter

Pix4Dsurvey terrain filter feature icon

Terrain filter

Pix4Dsurvey grid of points feature icon

Grid of points

Pix4Dsurvey TIN feature icon

TIN

PIX4Dsurvey contour lines icon

Contour lines

The Grid of points tool helps to automate the creation of spot elevations and allows for drastic simplification of the number of point cloud points. No new points are created, only existing points from the input data are used. 

Three types are available

  • The Regular grid is generated based on the selected sampling distance between points.
  • The Low-pass grid is generated based on a filter working on the Z-range.
  • The Smart grid creates points only where changes in terrain elevation occur.
 
Example: Comparison of the results of the Regular and Smart grid of points process. Notice how the Smart option generates points only where changes in terrain occur. Despite using the same Sample distance, significantly fewer points are generated while accurately describing the terrain, which makes the output files smaller and easier to import into CAD or GIS software.

Pix4Dsurvey grid of points regular points

Regular grid (293.290 points)
Sample distance: 1 m

Pix4Dsurvey grid of points regular points TIN

Regular grid and TIN

 

Pix4Dsurvey grid of points regular TIN

TIN

 

Pix4Dsurvey grid of points smart points

Smart grid (15000 points)
Minimum grid spacing: 1 m
Maximum number of grid points: 15000
Maximum elevation variation: 1 m

Pix4Dsurvey grid of points smart points TIN

Smart grid and TIN



Pix4Dsurvey grid of points smart TIN

TIN



 
Access:
  • Click Process Pix4Dsurvey process icon or,
  • On the Menu bar, click Process > Grid of points or,
  • On the Content panel, click TIN > Grid of points > Pix4Dsurvey processes button.

Processing options

Input point cloud

Defines the point clouds used for the Grid of points process:

  • All: All point clouds in the Content > Point clouds are used for processing. 
  • Only visible - default. Only visible point clouds in the Content > Point clouds and Terrain classes are used for processing.
  • Terrain - default if Terrain points are available: All points in the Terrain class are used for processing. Only available after the Terrain filter is processed.
  • Non-terrain: All points in the Non-terrain class are used for processing. Only available after the Terrain filter is processed.
 
Example: When the Terrain option is selected, only points classified as terrain class are used for processing.

GridOfPointsTerrainSetting.jpg

Only the Terrain class is used for processing.

Regular grid of points

A Regular grid is a simple rectangular grid that is decimated based on the selected Sample distance between points.

  • Grid spacing [units]: Determines the grid size:
    • 0.1 m - 30 m, 2.5 m - default.
    • 0.3 ft - 100 ft, 8 ft - default.

Low-pass grid of points

The low pass grid is generated based on the point cloud points within each cell based on the Grid spacing (sampling distance). Within the cell, the low pass looks at the vertical distribution and selects a point in the correct vertical slice.

  • Grid spacing [units]: Determines the grid size:
    • 0.1 m - 30 m, 2.5 m - default.
    • 0.3 ft - 100 ft, 8 ft - default.
  • Z-Range [arbitrary units]: Determines the altitude of the filter along the Z-axis.
    • 0 - 10, 1 - default.
 
Example: The Low-pass grid can be useful in the case of a highly vegetated area. In such conditions, with a Z-range value on the lower end, the points of the grid will be on the ground. On the other side, with a Z-range value on the higher end, the points of the grid will be on the canopy.
In the following example, a Z-range of 0 was used.

PIX4Dsurvey Low Pass Grid Animation

A vegetated area where the Low-pass grid type was applied. The point cloud is removed to make the resulting TIN based on the grid of points more visible.

 

 
Video: The following video shows the effect of the Low-pass grid on a LiDAR dataset. Even in forests or undergrowth, you can still include ground points.

Smart grid of points

A Smart grid attempts to generate just the most important points that define the terrain.

Based on the grid spacing, the number of grid points, and elevation variations the algorithm avoids creating redundant points on planar areas and focuses on generating points only where changes in terrain occur.

The following parameters can be adjusted: 

  • Minimum grid spacing [units]: The initial grid spacing that is used as a starting point for finding the most important points.
    • 0.1 m - 30 m, 2.5 m - default.
    • 0.3 ft - 100 ft, 8 ft - default.
  • Z-Range [arbitrary units]: Determines the altitude of the filter along the Z.
    • 0 - 10, 1 - default.
  • Maximum number of grid points: The maximum possible number of grid points in the final result.
    • 3 - 500000, 1000 -  default
  • Maximum elevation variation [units]: The maximum elevation variation from neighboring points.
    • 0.01 m - 5 m, 0.05 m - default
    • 0.03 ft - 16 ft, 0.15 ft - default

Results

 
Access: Results of the Grid of points process are available in the Content > TIN > Pix4Dsurvey grid of points icon Grid of points panel.

GridOfPointsTerrain.jpg

A regular grid of points (yellow points) generated only using the terrain points with a sample distance of 2.5 m.

 
Tip: Significantly fewer points are included in the results of the Grid of points process than in the input point clouds. We recommend right-clicking on the Grid of Points in the Content panel and increase the size of points for better visibility.

Export

The result of the Grid of Points process can be exported in .dxf, .shp, and geojson format. More in the Export article.

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