Creating Breaklines using the LP360 Sketch Tool

The LP360 Sketch Tool is a custom ArcGIS™ sketch tool that adds custom functionality to the out-of-the-box ArcGIS sketch tool. The LP360 sketch tool operates the same as the ArcGIS sketch tool. The LP360 Sketch Tool is only available in LP360 for ArcMap.

The LP360 Sketch Tool can use the ArcEditor snapping options in the same manner as the ArcGIS Sketch tool does:

ArcEditor Snapping Tools

However, using any of the ArcEditor Vertex tools, such as the reshape or edit vertices, will result in the z values of the vertices being incorrect and the conflation task will need to be run again. The best method is the use the z vertex options available within LP360 and explained below.

How to Use the LP360 Sketch Tool

  1. As a prerequisite to using the LP360 Sketch tool, make sure you have started an editing session from the ArcGIS Editor toolbar.
  2. Select Create Features within ArcGIS.
  3. Select the Target dataset to digitize features.
  4. Select your desired active “Conflate Task” from the LP360 Digitize Breaklines toolbar.
  5. Now you may select the LP360 sketch tool and begin digitizing features.
  6. Digitize at least one vertex before using the advanced keyboard or mouse options outlined below.

The following are additional keyboard and mouse options that are only available when using the LP360 Sketch Tool.

Viewer Integration (‘P’ Key)

The LP360 sketch tool can integrate the 2D map view with the profile viewer as a feature is being digitized within the map. This is very useful for digitizing features on top of banks or in stream channels as the profile acts a guide for locating the top of bank or the channel. The following illustration uses the integration with the profile for locating a stream channel.
Integration with the profile
To turn on the integration with the profile, the user must press the “P” key while using the sketch tool. Once the sketch geometry has at least one vertex, the profile will then be placed perpendicular to the direction of the rubber band segment in the sketch geometry. The cursor location is displayed as a vertical white line within the profile viewer. To disable the profile tracking, press the “P’ key again. If the profile viewer is not open when pressing the “P” key, it will automatically open the profile viewer (Note: some adjustment of the profile size may need to be made).

To freeze the location of the profile and slide the cursor into a channel or on top of a bank, press the “S” key to toggle the sliding state of the sketch tool. When activated, sliding will freeze the profile and allow the user to slide the cursor along the profile. Sliding is deactivated upon pressing “S” again or left clicking in the map to commit the vertex to the sketch geometry. The following illustrates the use of the slide function to freeze the profile and to slide the cursor into the channel.

Slide function to freeze the profile
On-the-Fly Refresh While Digitizing (‘F’ Key)
The LIDAR surface can be refreshed as the user digitizes a proposed breakline by pressing the ‘F’ key to toggle the on-the-fly refresh option. The on-the-fly refresh of the surface while digitizing can be useful in order to visualize the surface before committing changes to the LIDAR and feature databases. The following shows an example of using the on-the-fly refresh during the creation of a flat water body polygon.

Using the on-the-fly refresh
In the example above the user selected an on-the-fly refresh property to define the elevation that was used for the polygon during digitizing.

The on-the-fly refresh setting may also be used with conflation methods such as downstream constraints for creating hydrology centerline features. The example below uses a combination of z locks (see discussion the Z Lock Option; ‘L’ key) and the on-the-fly refresh to visualize the surface before committing the centerline to the database.

Downstream constraint algorithm produced an error
In the example illustration above, the downstream constraint algorithm produced an error when conforming the digitized line to the surface taking into account the z lock positions (i.e., assigned elevations in yellow, and black on the screen). The vertex producing the error is highlighted by the red circle. Upon inspection of the z lock values, you will see that the last digitized vertex is higher than the previous z lock position creating an unsolvable situation for the algorithm. Using the ‘D’ key on the current z lock position (i.e., designated in yellow) will lower that elevation of that vertex allowing the algorithm to complete the conforming criteria. Lowering the z lock position will refresh the surface and allow you to see the lowered surface as you decrease the elevation. Raising and lowering z lock positions are discussed in more detail below in the discussion of Locking Z Values.

Locking Z Values (‘L’ Key)

While digitizing breaklines, the user may override the current conflation task’s method for calculating an elevation by assigning an elevation manually over the entire feature (i.e., constant), or for individual vertices. When Z Locks is turned on information about the current state and settings being used is displayed at the position of the cursor. The following options/keys can be used when the Z Lock option is turned on.

As Constant and For Vertex Z Lock Values (‘H’ Key)

  • Constant Values: If you are using the ‘As Constant’ setting the z value that is displayed with the cursor location is the z value that will be used for the entire feature.
  • As Vertex Values: As vertex values allow the user to assign elevations for specific vertices within the digitized feature. Regardless of the conflation method that is used by the active conflation task, the elevations assigned to the vertices will not be modified. Assigned elevations are displayed beside the vertices. If the elevation is displayed in yellow it is the current z lock position and all subsequent operations that work on the current z lock position will modify that elevation (e.g., R, U, D keys). Elevations for all other z lock positions are displayed in black.

Interpolation Method (‘I’ key)

When capturing elevations using either the constant or vertex setting, an interpolation method is used to determine the z value assigned to a feature or vertex. The ‘I’ key is used to change the current interpolation method. Each of the following methods use the display filter and breakline enforcements of the active LAS layer if applicable:

  • Surface Z: obtains the z value from the LIDAR surface.
  • Lowest Z: obtains the lowest z value of the points within the current snapping tolerance.
  • Highest Z: obtains the highest z value of the points within the current snapping tolerance
  • Average Z: obtains the average z value of the points within the current snapping tolerance.
  • Closest Z: obtains the z value from the closest point.

Ready and Idle State (‘W’ key)

The state of the z lock option is either in an idle or a ready state. Pressing the ‘W’ key will toggle the state from ‘Idle’ to ‘Ready’ and vice versa. An ‘Idle’ state means that no elevation is being captured with the next left mouse click for assignment to the feature or a vertex. An idle state however does not mean a previously assigned elevation to a feature or vertex will not be used when digitizing is completed. The ‘R’ key must be used to remove the current z lock or the z lock option must be turned off in order to reset all z lock positions.

The ‘Ready’ state means that an elevation will be captured and assigned on the next left mouse click to a feature or a vertex. If using the ‘As Constant’ option the ‘Ready’ state does not change the value of the assigned elevation once an elevation has been captured for the feature. If the user wishes to recapture or reset the elevation used for the feature, press the ‘E’ key and the z lock state will be ‘Ready’ to capture an elevation on the next mouse click.

Resetting a Z Lock (‘E’ key): For ‘As Constant’ use only

While using the constant option, the user may decide to reset or recapture the elevation assigned to a feature. Use the ‘E’ key to reset the elevation used for a feature. After using this key the z lock will be placed in a ‘Ready’ state. The ‘E’ key has no defined use when using the vertex option.

Removing a Z Lock (‘R’ key)

After capturing the elevation value to be used for the feature or vertex, the user may remove a z lock position by pressing the ‘R’ key. When using the constant option, the z value assigned to the feature is removed and the state of the z lock option is idle. When using the vertex option the current z lock position (i.e., displayed in yellow) is removed and the state of the z lock option is placed in idle. To place the z locks back into a ‘Ready’ state to recapture the elevation, press the ‘W’ key.

Nudging Z Lock Positions Vertically (‘U’ and ‘D’ key)

The assigned elevation value for a feature or a vertex can be pushed up or down along the z axis by using the ‘U’ and ‘D’ keys respectively. When used in combination with the on-the-fly refresh option, the surface will be updated as the z lock value is pushed up or down.

About the Z Increment Amount
When nudging sketch geometry up or down using the LP360 Sketch tool, the sketch geometry is adjusted along the z axis by an increment amount. You may change this increment amount to best fit your project.

How to Modify the Z Increment

  1. From the Options button on the LP360 Digitize Toolbar, left-click the Z Increment Value Command.
  2. Input a new Z Increment Value into the dialog. The units are in the vertical units of the point cloud data.
  3. Press Enter to commit the new value or the ‘X’ icon in the upper right hand side of the dialog to cancel.

Making Z Lock Positions the Current Position or Creating Z Lock Positions for Existing Vertices

Generally z lock positions are assigned on a left mouse click when placing vertices in the digitized feature. Sometimes it may be useful for a user to assign a z lock position to a vertex after it has been placed in the sketch geometry, or make an existing z lock position the current position. Right clicking on the vertex for which you want to assign or make the current z lock position will display the context menu for a vertex. Select the ‘Set Vertex to Current Z Lock’ command to create or make that vertex the current z lock position. If the vertex is not already a z lock position, the current interpolation method will be used to get a default elevation for the vertex before making it the current z lock position. Selecting the ‘Set Z Lock Height’ command will perform the same functionality except allowing the user to input an elevation manually using a simple input dialog.

The Set Vertex to Current Z Lock command allows the user to create a lock position for an existing vertex in the sketch geometry. This command can also be used to make an existing z lock position the current z lock position. When invoked on a vertex where an existing z lock position does not exist, the current interpolation method is used to create a default value. This command is located on the context menu for a vertex when using the LP360 Sketch Tool and will only be enabled when using the Z Lock and the ‘For Vertex’ option.

Setting specific elevations manually for a feature or vertex

The user may assign an elevation to the feature or a vertex by right clicking on a vertex and selecting the ‘Set Z Lock Height’ command. The user will be presented with a dialog box where an elevation can be input manually. If the vertex or feature is not already assigned an elevation, the current interpolation method will be used to get a default elevation. Press Enter to accept the elevation or click the ‘X’ button to cancel the dialog.

Tips

  • Make sure you have access to an LP360 Standard license or higher
  • The sketch will not complete if:
    • Files are not open for read/write and the conflate task is set to reclassify
    • Conflicting user z locks with conflate task
  • The sketch will not have z values if the the ArcGIS sketch tool is used instead of the LP360 sketch tool
  • Make all modifications (right-click menu options) to elevation values before sketch is finished
  • Once a sketch is completed it cannot be edited with the creation tools

Check the following FAQ if the LP360 Sketch Tool is showing as disabled when attempting to digitize.

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