HOW TO

Determine the routes that fall within the densest area generated by the Line Density tool

Last Published: April 25, 2020

Summary

The Line Density tool is used to calculate the density of linear or polyline features that highlight high and low density areas on a map. Sometimes, polyline features that fall within the radius of the output raster cells are used to study how they influence the density of the surrounding area. The image below shows a route (polyline feature) in an area used as an example in this article.

Road polyline feature layer

Procedure

The following instructions describe how to determine routes that fall within the densest area generated by the Line Density tool.

  1. In ArcMap, run the Line Density tool from the Spatial Analyst toolbox on the polyline feature (in this article, the polyline feature is named 'road') to calculate the density of the polyline surrounding the output raster cells. Refer to ArcMap: Line Density for more information.
    1. Open a new blank project in ArcMap, and add the desired polyline feature to the data frame.
    2. In ArcToolbox, navigate to Spatial Analyst Tools > Density > Line Density.
    3. In the Line Density dialog box, click the Input polyline features drop-down, and select the polyline feature. Set a name for the Output raster, and click OK.
Labelling Properties

The image below shows the output raster from the Line Density tool.

Output Raster
  1. Use the Int tool from the Spatial Analyst toolbox to convert the output raster cells to integers.
Note:
The Int tool is used because the raster cell values in the Line Density tool are in decimals. The output raster cell values must be in integers when used in the next step. Refer to ArcMap: Int for more information.
  1. In ArcToolbox, navigate to Spatial Analyst ToolsMath > Int.
  2. In the Int dialog box, click the Input raster or constant value drop-down, and select the output raster created using the Line Density tool in step 1. Set a name for the Output raster, and click OK.
Int dialog box

The image below shows the output raster created using the Int tool.

Output raster from Int tool
  1. Use the Raster to Polygon tool on the output raster created in step 2 to convert the raster layer to a polygon layer. Refer to ArcMap: Raster to Polygon to do this.
    1. In ArcToolbox, navigate to Conversion Tools > From Raster > Raster to Polygon.
    2. In the Raster to Polygon dialog box, click the Input raster drop-down, and select the output raster created using the Int tool in step 2. Set a name for the Output polygon features, and click OK.
Raster to Polygon dialog box

The image below shows the output polygon feature layer generated using the Raster to Polygon tool.

Raster to Polygon tool output
  1. Use the Spatial Join tool to join the polyline feature and the polygon feature created in step 3 to determine the routes intersecting the polygon features. Refer to ArcMap: Spatial Join for more information.
Note:
This step is carried out to identify the routes related to the polygon feature, which are determined by the names and number of intersecting routes.
  1. In ArcToolbox, navigate to Analysis Tools, > Spatial Join.
  2. In the Spatial Join dialog box, click the Target Features drop-down, and select the polygon layer from step 3. Click the Join Features drop-down and select the polyline feature layer. Set a name for the Output Feature Class.
Note:
Ensure Join Operation (optional) is set to the JOIN_ONE_TO_ONE option. 
Spatial join dialog box
  1. In the Field Map of Join Features (optional) section, right-click Name(Text) > Properties.
Field Map of Join Features (optional) section
  1. In the Output Field Properties dialog box, change the text to a desired length. Click Merge Rule > Join. Press the comma keypad for the Delimiter option. Click OK.
Output Field Properties dialog box
  1. Back in the Spatial Join dialog box, scroll to the Match Option (optional) drop-down, and ensure it is set to INTERSECT. Click OK.
Spatial Join dialog box
The image below shows the output polygon feature layer generated from the Spatial Join tool. 
Spatial Join layer output
  1. In Table of Contents, uncheck the raster layer check box created in step 2, and the polygon layer check box created in step 3.
Table of Contents
  1. Click the symbol icon of the spatial join layer created in step 4.
    1. In the Symbol Selector dialog box, change the colour of the spatial join layer to Hollow.
    2. Set the Outline Width to 1.
    3. Click OK to close the Symbol Selector dialog box.
Spatial join layer
 
 
Symbol Selector dialog box
  1. Click the Identify tool, and, zoom in to the polygon layer with the densest region. Click the layer to view the routes that fall within the densest area generated by the Line Density tool.
Densest route with the names

Article ID: 000021998

Software:
  • ArcMap

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