Set Line Direction (Topographic Production Tools)

Summary

Sets the direction of line segments to match the slope direction of underlying elevation features. The direction of a line is used by some of the generalization and cartography tools.

Usage

• This tool updates the line segments in the features of the Input Line Features parameter value so that each line segment flows in the correct direction according to the Digital Elevation Model parameter value.

• The Line Direction parameter option will determine how the direction of the line segments are set.

  • Downhill—The end points of a line segment will be used to determine the direction. The end with the highest elevation will be set as the start of the feature.

  • Downhill Flow—Nearby features will be taken into account using the flow network composed of the input features, such as hydrology lines, and the line orientations will be set consistent with the network's overall flow.

  • Downhill Split Flow—The tool processes the same as Downhill Flow, except line features may be split into new features to ensure flow direction with regard to vertical tolerance. Splitting may occur if the slope changes direction or the lines are not split at intersections.

• If the Reverse Direction parameter is checked, the direction of the line features will be inverted so that the start vertex represents the lowest elevation.

• If specified, the Vertical Tolerance parameter value will be used to normalize the lines by filling dips and peaks when an input raster is not reliable or the input features don't overlap with the points on the raster. It is also used to handle the flow direction of a flat area.

• If a vertical or projected coordinate system is set as the spatial reference, the Vertical Tolerance parameter value is converted to the units of the raster. Otherwise, the raster units will be meters.

• The tool's results rely on hydrologically correct DEMs.

• The integrity of the results of this tool relies on the topological integrity of the Input Line Features parameter value:

  • Connectivity—Proper connections must exist at intersections to accurately represent the connectivity of the line network. Lines must be split at all true intersections. Use the Feature To Line tool to split lines at all intersections. Alternatively, use the Must Not Self-Intersect and Must Not Intersect Or Touch Interior topology rules to resolve these issues.

  • False dead ends—A false dead end is an unconnected segment that appears connected when symbolized at the final map scale. These may be areas where you expect connectivity based on appearance, but the features are not actually connected. Proper connections must exist at intersections to accurately represent the connectivity of the line network. Use the Extend Line or Snap tools to ensure that the line segments touch.

  • Single–part features—The input features cannot contain multipart features. Use the Multipart To Singlepart tool to convert multipart features to single-part features before running this tool. Alternatively, create a topology with a Must Be Single Part rule that converts the multipart features to single-part features before running this tool.

  • Pseudo nodes—A common endpoint shared by no more than two lines is also known as a pseudo node. If the attributes of the two lines match, the features can be merged without losing information. Use the Merge Lines By Pseudo Node tool to remove unnecessary nodes.

Parameters

• Dialog
• Python

Label	Explanation	Data type
Input Line Features	The line features that will be modified.	Feature Layer
Digital Elevation Model	The input elevation surface that will be used to evaluate the Input Line Features parameter value.	Raster Layer; Mosaic Layer
Line Direction (Optional)	Specifies how the direction of the line segments will be set. Downhill—The line segment direction will be downhill. Downhill flow—The line segment direction will use a flow network created by the input line features and adopt the direction from high values to low values. This is the default. Downhill split flow—The same as Downhill Flow, except that the line features may split at hill tops or junctions to ensure the direction of flow with regard to vertical tolerance. This option may create new features.	String
Reverse Direction (Optional)	Specifies whether the line features will be reversed along the flow direction. Checked—The line direction will be reversed. Unchecked—The line direction will be maintained. This is the default.	Boolean
Vertical Tolerance (Optional)	The minimum difference in elevation between raster values before they are considered equal. The default is 0 meters.	Linear Unit

Derived output

Label	Explanation	Data type
Updated Line Features	The Input Line Features parameter value with updated line segment direction.	Feature Layer

Environments

This tool does not use any geoprocessing environments.

Licensing information

• Basic: No
• Standard: No
• Advanced: Requires Topographic Mapping

Related topics

• An overview of the Generalization toolset
• Find a geoprocessing tool