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Convert polyline segments to ARCS

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Having had another quick glance at the data, I believe that straight lines are not subdivided. This is easily seen if grips are used. Where there is a single grip in a 'straight' line, closer inspection reveals that the line bends at the grip.


I am afraid that there are not curves everywhere the lines change direction, so manual input is required if you must have a curve between straights.

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@gsc I don't know of a way to do this automatically; there would be no way to determine if the segments represented an arc or not.   This could be done in a program manually however by selec

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Agree with you Eldon that is why need 1 pline with all the  data straights and curves from the GIS, this is the only way can really say where is an arc. 


GSC a question if there is any change in a line direction can there be a 0 radius ?


GSC This is the length and angle of segments at start so is there arcs ? A manual check matches the initial 102.122 as a straight.  So are shorter lengths a arc? Further in the segments the 6.803 is repeated like 15 times so is accepted as an arc. 


((102.122 5.49781) 
(6.80382 5.51482) 
(5.83184 5.54884) 
(7.7753 5.57861) 
(6.80382 5.61688) 
(6.80382 5.6509) 


Really need the method used when exporting to autocad what are the GIS rules then can work backwards. I had the advantage that the other department was our GIS section so we could ask them these questions.

Edited by BIGAL
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Posted (edited)
On 3/28/2021 at 12:09 AM, BIGAL said:

Is it a change in direction ?  Like you there was a Line line line at the start of the pline I picked. Need GSC to confirm with some real plines what is actually going on need to compare to the GIS original then can do some rules. Looking at the formula link seems the way to go. The sample dwg is fine for testing. But need a list of all the curve details for at least one pline so can compare.


The one item may be that a straight is always longer than x. And no radius greater than Y.



144392-XREF-0010-IAC Routes-03.dwg



There (sometimes) are some routes which have such a small route change that apparently the curve angle was too small for GIS to divide the curve in more than 1 vertex.
In this case only one vertex was placed

In my attached sample I have re-traced 3 random routes with the PLINE function switching between Line and Arc, but always selected the start and end vertices of an (assumed) curve.
After tracing I have added dimensions to check the radius. In this drawing, in all 3 cases the arc values have a rounded number.

The routes in this project have a clear difference between the length of a straight and curve segments.
But sometimes we also receive routes divided (straights and bends) into 1.0m or 0.5m steps (this happens because engineering companies who are hired by the client probably are using different pipeline/cable routing software), which makes it more difficult to select the correct start and end point of the arc.

Note: a route always starts and ends with a straight

144392-XREF-0010-IAC Routes-03.dwg

Edited by gsc
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Your drawing rather proves my misgivings that all the proper data is not available - you have missed one bend and one of the radii is wrong!


However, I maintain that your method of working by tracing the existing vertices would not produce the desired outcome in all cases. I think that drawing the straights and then joining them using Fillet with the desired radius ensures that all connecting arcs are truly tangential.



Missed one.PNG

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I am sorry to be the bearer of more bad news, but in the recent drawing you posted, not all your arcs are tangential to the straight lines. I drew a line from the end of an arc to the centre of the circle and then to the other end of the arc. These lines should be at precisely 90° to the straights. They are not. At one end they are, and this shows up the method you are using to draw the polyline. When you change from line to arc, the arc is constrained to be tangential to the previous line. But at the end of the arc, the next line is NOT tangential to the arc. I have always found this to be an annoying failing in the process. Instead, draw the straights and fillet between them using the known radius. This ensures both ends are truly tangential.



Not right angles.PNG

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9 hours ago, gsc said:


.....Note: a route always starts and ends with a straight



And then I found one that didn't!  Probably the only one that ends in a curve.



End curved.PNG

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