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Problem: Unable to draw parallel lines in a geographic coordinate system in ArcGIS Pro

Description

In ArcGIS Pro, when drawing a parallel line using the Parallel function on a dataset in a geographic coordinate system (GCS), the line drawn is not parallel to the original line. Instead, the line is drawn at a certain angle as shown in the image below.

Non- parallel lines

Cause

This is expected behaviour. The parallel function does not work with a Geographic Coordinate System. This is because the parallel lines are drawn onto a 3D surface in a GCS which follows the curvature of the earth.

Solution or Workaround

To resolve this issue, use a projected coordinate system (PCS) for both the dataset and the map view where the map is projected onto a flat surface. To do so, use the Project tool. Refer to ArcGIS Pro: Project for more information.

The image below shows the parallel line created when using a projected coordinate system.
 
Parallel lines
 
Note:
If the lines are drawn in 3D scene, which by default is in a GCS, the line becomes curved as it respects the curvature of the earth.

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