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Commands and options to switch or reverse geometry direction

by Technical Evangelist on ‎12-19-2016 09:22 AM (559 Views)

Question

What commands and options can be used to switch or reverse the direction of a polyline geometry?

Answer

The following 2 reverse options are available for editing of existing geometry stored in a read-write warehouse connection (Access, MS SQL, MS SQL Spatial, Oracle or PostGIS):


GeoMedia Reverse Direction command can be used to interactively reverse the direction of a selected linear geometry. Geometry Information command supports right-click actions, one of which is Reverse. To use the Geometry Information command, select a geometry then right-click in the map window for the Geometry Information option.

 

The Functional Expression system is used in commands such as Functional Attributes, Aggregation, Analytical Merge and Update Attributes. The Update Attributes command requires a read-write connection, the other commands support both read-only and read-write warehouse connections. The Functional Expression system has a REVERSE geometry function.


The following expression would reverse all of the geometry of the input record set:


REVERSE(Input.Geometry_Field_Name_Here)


The following expression uses an IF statement to reverse only the geometry of records where the attribute field called ONE_WAY = “Yes”.


IF(Input.ONE_WAY = “Yes”, REVERSE(Input.Geometry), Input.Geometry)


This can be logically read as: If the one-way is “Yes”, then reverse the geometry but if one-way is not yes, then keep the original geometry.

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