Clipping Breaklines Results in Zero Z-Values for Some of the Output Lines

[Anonymous User]

Original User: gmbacon

[ATTACH=CONFIG]23076[/ATTACH][ATTACH=CONFIG]23077[/ATTACH]Hello. 

I am working with county-wide mass point elevations and breaklines to create TINs.  Before creating a TIN, I clipped the mass points and breaklines to work with a smaller area and noticed artificial depressions appearing in the TIN where some breaklines lost their elevation values and were set to zero.  I didn't realize this happened until I created the TIN and noticed depressions like the one I've attached.  Before the clip, this breakline had z-values of about 372-373 feet (see second attachment). 

The only way to avoid these false depressions is to process the very large datasets, without clipping, and hoping for the best.  Sometimes the processing completes, sometimes it doesn't.  Any suggestions for a resolution are greatly appreciated.

Thank you.

[JeffreySwain]

I would consider using the polygon that you used to clip as a soft clip rather than how you are clipping the breaklines. It appears that if your breaklines are losing their elevation is that either you are making them 2d.  The soft clip will restrict what will be considered and not use the z of the clipping polygon.

[Anonymous User]

Original User: gmbacon

I will try this but my reason for clipping the dataset before creating the TIN was to work with less data and actually get a result.  Also, why would only some of the breaklines lose their z-values while others retained them after the clip?

[LukeSturtevant]

I have had the same problem described in this thread. I thought maybe it was due a discrepancy in projections for the feature classes, but that is not the case. The only way I have been able to bypass the clip tool in order to preserve Z values is to:

1. Run Intersect with the polygon and polyline Z feature to output intersection points

2. split line at intersection points

3. select line that have their centroid inside the polygon

4. switch selection and delete features

This clips the lines, but retains all the Z values. It is very unfortunate that there are so many steps in order to do exactly what the clip feature should do. Hopefully someone else comes up with a better work around or ESRI fixes whatever might be happening in the clip process.