Polyline Z to Buffer with same Z dimensions??

[MorganHarris]

Does anyone know how I might be able to take a polyine z and create a planar buffer that extends horizontally, but retains the same vertical contour as the polyline? Buffer 3D seems to only create a tubular buffer around the line and the buffer tool in analysis creates a planar buffer, but it is not a polygon z and therefore does not retain the same shape as the polyline z. Any suggestions?

[EstebanHerrera]

If i'm not wrong, yes, it is possible, you just have to choose in the options while creating the buffer that you only want it in a specific direction

[RaymondHuang1]

Just curious about your question, are you trying to create a 3D buffer around the polyline that has a volume? Or are you looking to create a 2D buffer with the line's z value as the distance to buffer?
​
Regards, 
​Raymond

[MorganHarris]

Sorry, you're right. That wasn't very clear in my question. I am trying to create a 2D buffer that extends from a polyline that is in 3D space. So , I do not want a buffer that has a volume, I just need one that follows the same shape as my polyline. In this specific example I have a polyline that represents a power line in 3D space and I need to create a planar buffer that has the same shape and height as the power line. The issue is that power lines sag, so they are not straight lines, but when you use the 2D buffer function it does not retain that 'sag' in the buffer. I hope that makes it more clear!

[RaymondHuang1]

Thank you for clarifying. However, there is no straightforward way that you can achieve this in ArcGIS for Desktop. May I ask how do you intend to use such planar 3D floating buffer polygons? Is it for viewing purposes only?
​

[MorganHarris]

I am trying to use this buffer to create a raster surface with power line height so that I can automate the process of subtracting vegetation height from power line height at different buffer distances. We are trying to figure out how vegetation heights around power lines at different distances away from the power lines affect seabird flight.

[RaymondHuang1]

I see. I believe it is more tedious to achieve this in vector. How about try doing it in raster form then?

I can imagine the workflow to be such:

From your line with elevation, create a raster presenting your line with its elevation as the raster value.

Then use the Expand tool to expand your raster representing the line by the number of required cells calculated by the distance required divided by the cell size. This essentially creates a ‘buffer’ for you in raster form with the necessary elevation values in each cell.

Let me know if this workflow works for you.

[MorganHarris]

I tried this method and I thought it was going to work really well, BUT since the line itself is sloping and not a constant value there is no way to assign a value from the attribute table to the raster so that the raster retains that slope of the line (at least not that I could figure out). The resulting raster only had two values containing what I believe is the average elevation of the power line.

The only way that I have been able to work this out is to take my points derived from LiDAR that contain the elevation of each point and copy them and move them to the required distance away from the original points then create a TIN that connects the original points to the copied points. This creates a sloping TIN that follows the power lines. From that TIN, I can then create a raster with the elevation value that is representative of the shape of the line. The raster is the end result that I wanted, so that is why I was really hoping the method you presented would work. Let me know if you know of a way to make the raster follow the slope of the line rather than be represented as one elevation. Thanks for your input!

[MorganHarris]

Esteban, buffering in a specific direction is possible, yes, and I know how to perform that task. Refer to my reply to Raymond for a more detailed explanation of my question. Thanks!

[MorganHarris]

Esteban Herrera‌ and Raymond Huang‌

If you are still interested in this discussion then you should take a look at this picture. I was watching a video for power line corridor mapping and hazard tree detection (Resource Management & Power Line Encroachment Applications: E3De LiDAR Exploitation - YouTube)‌ and at the end of the video they just mention: "and then you can create a buffer in arcscene and use the intersect tool to see where the trees are taller than the power lines". They make it seem like this is a well known function, but I can't find any tool that allows me to create a buffer like that (i.e. one that has the same z dimensions as the 3D line, but is a flat surface). Anyway, maybe this visualization will spark some inspiration and help get what I need to do across a little better.