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uniDEM Centerlines

uniDEM supports the delineation of vector centerlines. These are helpful during editing features like rivers, roads, streams and adding breaklines or constructing features. Centerline delineation can be performed manually (Draw Nodes) or in a semi-automated manner (Trace in Class).

Geometries are collected and can be applied to different classifications as selected in the Class dropdown. When Draw Nodes or Trace in Class are active the views are drawn partially transparent. This allows nodes (vertices) to be drawn above and below the terrain as needed to better model the underlying terrain.

This figure illustrates the collection an application of monotonic river steps to an unedited drainage. See more examples below.

Town Line Brook Canal, Massachusetts, US

Draw Nodes

Selects the Geometry tool for drawing centerlines and creates a new layer of the selected class type if one does not yet exist.
When activated the views will be rendered with transparency so nodes and lines added beneath the terrain can be viewed.

Geometry vectors are collected by holding Shift+Left-Click where each node (vertex) is to be placed. Added nodes exist in three dimensions and are used to delineate the center of a classified feature or to quickly flatten linear features of a fixed width.

Nodes can be one of three types based on the selected Node Z Mode.

The horizontal location of a node can be modified by:

  1. Holding Shift+Left-Click to select the node for movement
  2. Dragging the node to the new location while continuing to hold Shift+Left-Click

The elevation of a node can be modified by:

  1. Holding Shift+Left-Click to select the node for movement
  2. Holding Shift+Right-Click and selecting Set Elevation
  3. OR Holding Shift+Left and Right-Click and moving the mouse to raise (forward) or lower (backward) the elevation

Geometries are not just single line vectors but can be used to draw a network topology of intersecting vectors. To connect one vector to another hold Shift+Right-Click over the target node and select Connect.

Default shortcut: none

Trace In Class

Geometry delineation of complex classifications can be automated using the Trace in Class feature. This tool uses a cost function to place a centerline between two points that are connected with a single classification.

To create a centerline for a river:

  1. Press Shift+Left-Click to add a node at the start of the river
  2. Press Shift+Left-Click to add a node at the end of the river
  3. uniDEM will add nodes between the two points that minimizes the distance while placing the connecting vector wholly within the classified river

Default shortcut: none

Class

The Class dropdown defines which classification will be used by Trace in Class and Apply.

Default shortcut: none

Node Z Mode

When drawing a Geometry points between the start and end of a vector can be set to one of the following options:

  1. Fixed: Nodes will sample the height at the xy position of the node when they are added
  2. Floating: Added nodes will continuously sample the height at the xy position of the node if the terrain height changes
  3. Interpolated: All nodes added will linearly interpolate the height from the closest defined heights of nodes along the same vector

At any time, the Node Z Mode can be modified by:

  1. Activating Draw Nodes
  2. Pressing Shift+Right-Click on the node
  3. Pressing Set Elevation
  4. Select the desired Node Z Mode

Default shortcut: none

Node Spacing

Defines the maximum spacing that can occur between two nodes when using the Trace In Class tool. Added nodes will be minimized by spacing them apart when creating the centerline, but will not be simplified below this threshold.

Default shortcut: none

Apply Centerline

Flattens a selected area using a defined centerline using either a prescribed width or a classification. For best results Apply Centerline should be used with a classification.

Default shortcut: none

Set Node Z in Area

All nodes in a selected area can be set to a defined elevation.

Default shortcut: none

Delete Nodes in Area

All nodes intersecting with a selection area are deleted.

Default shortcut: none

Examples

River Edit
These figures illustrate the collection and application of monotonic river steps to an unedited drainage.

Edit drainage across bridges

Drainage monotonically edited

Road Edit
These figures illustrate the collection and application of road flattening and the addition of removed bridge decks to a DTM.

Roadway classified

Roadways flattened and bridge decks added