How to create an outside boundary around a selected set of lines

I had this question come up today - a user asked if they had a set if closed polygon areas that partially overlapped and they wanted to find an outside boundary around all of them - how to do that without manually drawing a boundary

Two methods you can use to do this

Method 1
Draw a rectangle outside the area covered by the combined selection of polygons

Use the Track Region command, select the rectangle and the lines that you want to find the boundary of and check the track interior regions check box. Then select a point somewhere between the outer rectangle and the outer limits of the lines that you are trying to find the boundary of - this will create a line that tracks the outer rectangle and the inner area.

Now break the line to separate the inner area from the outer area and close out the inner area using the properties command and you should be good to go

Method 2
Give all the lines an elevation eg 100

Make a surface out of all the lines. Set the surface properties to eliminate triangles in areas that you don’t need or use trim surface edge to clean the outside areas of unwanted triangles

Use the create surface edge breakline to put an edge around the surface

You are good to go

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