LAS dataset Profile View

A common way to visualize, analyze, and edit lidar data is to use a 2D cross-sectional view. A selected set of lidar points from a LAS dataset can be displayed and edited using the LAS dataset Profile View window accessed from the LAS Dataset toolbar in ArcMap. Visualizing cross sections of lidar data allows you to analyze collections of points from a unique perspective. 2D profile perspectives may make it easier to recognize particular features captured from lidar data, such as surface valleys, mountain peaks, buildings, vegetation types, forest canopy, road corridors, river/stream corridors, mines, construction sites, towers, and even power lines. Drawing cross sections of these features allows you to validate your lidar data in GIS and enables you to make informed analytic decisions.

Using the Profile View window, you can do the following:

• Measure distances and heights between points.
• Manually edit and update LAS classification codes.
• Manually edit LAS point-bit field flags.
• Display full-resolution lidar point sets.
• Select the LAS dataset 3D View window to visualize the selected LAS dataset point set in 3D.

A full-resolution point set is displayed in the Profile View window. If a thinned set of points is shown in the ArcMap display window, the selection box used to create the 2D profile will only select a full-resolution point set to be displayed in the profile. The maximum number of points that the selection window will allow is based on the Point budget set. The point budget can be found on the Point Tool Options window, located on the LAS Dataset toolbar in ArcMap.

When lidar data is stored in LAS files, each point is often classified with a specific classification code that defines the type of feature that reflected the laser pulse. By using the Profile View tools, you can manually edit and update the classification codes for a single point or groups of points. Having the correct classification code assigned to each point will provide you with more accurate ways of filtering the points in your display. For more information on lidar classification, see Lidar point classification.

How to launch the LAS dataset Profile View

To open the Profile View window, follow the steps outlined below:

Steps:

1. Click the LAS Dataset Profile View button from the LAS Dataset toolbar.
2. With the crosshairs active, click a location on the point set that represents the starting point of the LAS dataset profile graph.

   A small dialog box appears, interactively showing the current length of the line. Use the SHIFT key to set straight vertical or horizontal lines. Press the ESC key to cancel.

3. Click a location on the point set that represents the ending point of the LAS dataset profile graph.

Once an ending point has been selected, a selection box appears allowing you to move the pointer until the box is at a desired profile width. The actual dimensions and point count for the selection box are displayed in a small dialog box in the ArcMap display window. These values change interactively as you move the pointer over the point set. The units of the displayed width correspond to the coordinates of the data being used for the analysis. When a maximum point count is reached, you cannot make the selection box any larger.

4. Click a third location to represent the width of the profile graph.

All-return lidar displayed as an elevation surface (Data courtesy of Merrick and Company)

Note:

• Points will be displayed even if the selection window is drawn on a surface. The surface view of a LAS dataset is not supported in the Profile View window.

• The Profile Graph tool on the 3D Analyst interactive toolbar is also available to generate profiles. This tool will only be available when the LAS dataset is displayed as a triangulated irregular network (TIN) surface. To learn more about the 3D Analyst profile tools, see Fundamentals of creating profile graphs.
• Launch the LAS dataset 3D View window to visualize the LAS dataset points that are currently shown in the 2D profile view in 3D full resolution.
• Use the +/- keys on the keyboard to increase or decrease the size of the points that are displayed in the Profile View window.

Profile View tools

There are several tools available for the LAS dataset points on the Profile View toolbar:

Navigate tool

The wide variety of functions built into the Navigate tool means it will most likely be the main navigation tool you use in Profile View. Clicking the left and right mouse buttons and dragging up, down, left, or right allows you to rotate the view, zoom in, and zoom out. Other navigation functions, such as setting the target location, are exposed through the use of keyboard shortcuts.

Zoom In tool

Use the Zoom In tool to zoom in to a target by clicking once and dragging a box in the Profile View window.

Zoom Out tool

Use the Zoom Out tool to zoom out from a target by clicking once and dragging a box in the Profile View window.

Pan tool

Use the Pan tool to move throughout the LAS dataset points in the 2D LAS dataset profile view.

Full Extent tool

Click the Full Extent button to zoom to the full extent of Profile View.

Refresh tool

Use the Refresh tool to refresh the data view to match the extent and symbology of the LAS dataset layer in the ArcMap window.

Point Information tool

Select the Point Information tool to display additional information corresponding to a selected lidar point. Once a point has been selected, by default, basic location and attribute information is displayed. Select the Show more LAS attributes check box to display additional LAS attribute information for the selected point. The graphic below depicts the Profile Information window that will be displayed.

Measure

Measure elevation and elevation difference between LAS points using the Measure tool .

Steps:

1. Click the Measure tool from the Profile View toolbar to measure elevation and elevation difference between two selected points.

2. Click a starting point to begin the measurement in the Profile View (Start).
3. Click an ending point in the Profile View to finish the measurement (End).
The elevation of the starting point, the elevation of the ending point, and the elevation difference between the starting point and ending point will be displayed in Profile View window.

Select points

Use the Select Points tool to select LAS dataset points from Profile View. Once the tool is selected, either click on a point to select point by point or drag a selection box in Profile View to select several points. Hold down the SHIFT or CTRL key to add to an existing selection.

Clear selected points

Use the Clear Selection button to clear selected LAS dataset points from Profile View.

Edit LAS dataset points

Use the Edit button to launch the Change Class Codes dialog box. This dialog box allows you to edit the classification codes and bit flags associated with the LAS points of the LAS dataset displayed in Profile View.

Profile View options

The Profile View Options button controls how the LAS dataset Profile View window appears. You can change Background color, Point size factor, and Point budget on the Profile View Options dialog box.