# Finding the furthest perpendicular point between two lines

Is there an easy way to wind the maximum perpendicular point between two lines?

I'm trying to find the maximum perpendicular distance between two lines and the measure tools don't seem to have a function for this. I'm currently copying parallel to find the point but it's a bit slow and imprecise, is there a better way of doing this?

The attached image should show what I'm trying to do.

Parents
• Offset the yellow line a significant distance beyond the red, and construct a minimum distance line between the 2

• Lorys

Currently Using V8iss10 (8.11.09.919)

and dabbling in CE  update 16 (10.16.00.80)

and  now

Pwise Administrator ( yeah I passed the training course!)

MicroStation user since 1990 Melbourne Australia.
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•  I  would  use  place circle  by edge and use  tangent and  perp snaps and Mstm will find the solution as the diam of the circle

That won't work either for the simple reason, how do you know that your chosen start point of the circle is precisely at one of the 2 possible furthest points? You're eye-balling it and that is not an accurate solution to the problem.

The idea of circle theory may not even be applicable; the op stated in the title and original post that its the maximum distance between 2 lines (not Circle/Arc). That what appears to be Circle/Arc in the image, may/may not be relevant. Regardless, the option proposed by both myself and MaryB is the only one which I can think of right now which will give the OP a way to accurately attain the maximum distance between 2 lines/arcs etc...

• how do you know that your chosen start point of the circle is precisely at one of the 2 possible furthest points?

I'm not so sure your right as if its an arc then tangent snap   from arc and  perpendicular to the  line should result in an mstn solving or solution.. maybe my test file was too simple  with an arc as  part of  semicircle and a chord 2/3  up from diameter but I like Jon's vba pretty clever...

Lorys

Currently Using V8iss10 (8.11.09.919)

and dabbling in CE  update 16 (10.16.00.80)

and  now

Pwise Administrator ( yeah I passed the training course!)

MicroStation user since 1990 Melbourne Australia.
click link to PM me

• maybe my test file was too simple  with an arc as  part of  semicircle and a chord 2/3  up from diameter

I'm absolutely correct without a doubt, I've tested your suggestion and found it doesn't work. Your description of your test case gave you false hope; by creating an arrangement of a perfect chord on a circle/arc, you automatically gained one of the furthest points via the mid point of the line. If you try a test with a different situation using a partial arc or line, you will find it will fail. Why? Simply because, the line's midpoint is no longer one of the furthest opposing points AND when using the command PLACE CIRCLE DIAMETER, MicroStation prevents perpendicular snap from being used (unlike with PLACE LINE as per Ron's suggestion) thus killing your idea immediately.

Only because you were able to key-point snap to the line's mid-point, were you then able to create the circle via tangent snapping to the opposing furthest point, but unfortunately as a reusable solution in all circumstances, the result was a false positive.

Ron's suggestion is the best answer to the OP's query.

• of your test case gave you false hope; by creating an arrangement of a perfect chord on a circle/arc

Ok my bad .. consider the point conceded but thanks for figuring it out where I was going wrong  .. but to be fair  I did go off the OP image as his example  but I didnt  think it thru enough about the top of the arc has to be the furthest point in a perfect case.. and I agree that Ron Jones  is the best and least effort  approach  for all situations... however the assumption was the OP wanted the Sagitta length ... ( which I often need in my work too) inspired Jon Summers to create and share his new VBA macro for which I'm grateful and others with definitely  benefit although serendipitously arrived at... and the create centre line is also awsome..

Lorys

Currently Using V8iss10 (8.11.09.919)

and dabbling in CE  update 16 (10.16.00.80)

and  now

Pwise Administrator ( yeah I passed the training course!)

MicroStation user since 1990 Melbourne Australia.
click link to PM me

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• of your test case gave you false hope; by creating an arrangement of a perfect chord on a circle/arc

Ok my bad .. consider the point conceded but thanks for figuring it out where I was going wrong  .. but to be fair  I did go off the OP image as his example  but I didnt  think it thru enough about the top of the arc has to be the furthest point in a perfect case.. and I agree that Ron Jones  is the best and least effort  approach  for all situations... however the assumption was the OP wanted the Sagitta length ... ( which I often need in my work too) inspired Jon Summers to create and share his new VBA macro for which I'm grateful and others with definitely  benefit although serendipitously arrived at... and the create centre line is also awsome..

Lorys

Currently Using V8iss10 (8.11.09.919)

and dabbling in CE  update 16 (10.16.00.80)

and  now

Pwise Administrator ( yeah I passed the training course!)

MicroStation user since 1990 Melbourne Australia.
click link to PM me

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