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Point thinning and scalability of a LAS dataset

The LAS dataset is scalable, allowing you to work with large point cloud datasets quickly and efficiently. Rendering very large point sets or TIN-based surfaces is generally quite difficult, partially due to limitations of hardware. LAS datasets are beneficial in that you render the areas you need to visualize at an optimized point resolution.

On-the-fly surface construction, display, and analysis are faster for smaller-scale applications because only a thinned subset of the data is required. LAS dataset tools facilitate the use of large point collections, such as lidar that normally pose display problems. Scalability is achieved through random point thinning. The original data is not moved or averaged in any way.

Consider rearranging the LAS points using the Extract LAS geoprocessing tool. Doing so will order the point records into spatial clusters that are optimized for reading the files and will dramatically enhance their display performance throughout the ArcGIS platform.

Typically the LAS points are displayed as a thinned representation of the full resolution point set. You can quickly zoom into full resolution using the Zoom To Full Resolution option from the context menu of the LAS dataset layer. Simply right-click the LAS dataset layer in the Contents pane and select Zoom To Full Resolution. The Zoom To Full Resolution option is only available in a 2D view.

The Appearance tab controls the LAS dataset layer's drawing behavior and point thinning. The Point Thinning group controls the resolution of the LAS dataset. The Point Thinning group is available in a 2D or 3D view.

Access point thinning options

Follow these steps to access the Point Thinning group.

  1. Select an LAS dataset layer in the Contents pane.
  2. On the Appearance tab, in the Point Thinning group, choose the applicable point thinning options for the selected LAS dataset layer.

Full Resolution—When Use scale to control full resolution is checked, a scale threshold can be set in the Full Resolution Scale window. This is a scale threshold used to control when the LAS dataset renders itself without thinning, using 100 percent of the LAS points. It is used when the map scale is equal to or greater than the scale you specify. The point limit is still honored; therefore, if the number of estimated points for the current extent exceeds the limit, the LAS dataset thins itself and will not draw using all the data. When this occurs, an asterisk displays next to the data percentage listed for the layer in the table of contents. When the map display scale is less than the full resolution scale, thinning occurs based on the setting of the Point Density slider bar.

Display Limit—Applying a point limit sets a size limit to the number of points used in the triangulation of the LAS dataset layer surface. The default value is 800,000. If, for a given display extent, use of the settings result in a surface that exceeds the specified point count, the layer switches to be more generalized.

Density—The density of points enforced by the LAS dataset. This is set interactively by using the slider bar. Move the slider to the left for a coarse surface and to the right for a more fine or full surface resolution. As you move the slider bar, the density of the points on-screen changes from Min to Max.

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