Crop a grid surface created from DEM tiff

[OliverE]

Hi,

Is it possible to crop a grid surface that has been created from .tif DEM file? I have a dwg that has one surface in it, named EGL. I didn't create the surface but believe it was created by right clicking Surface in prospector tab > Create Surface > Select Grid as surface type > Add DEM file. The current surface style only displays the surface border. The DEM has 38million points spread across a mountain that's being developed.

Future drone survey's will likely be used to update EGL. Therefore, I would like to crop three sections of this surface representing different stages of the project to be used by multiple people for simultaneous design. I have three closed 2D polylines at 0 elevation representing each stage. The Create Cropped Surface dialogue box has the surface type greyed out and only TIN surface is available as the surface type that I'm able to create which I'm not overly worried about but any comment here is welcome too. I'm experiencing two issues:

1) I select EGL > Extract From Surface>Create Cropped Surface>click Selection Method>Select Object on the command line. It cancels the command and the Create Cropped Surface dialogue box re-opens. 

2) If I follow the same steps but draw a polygon rather than trying to select one of the polylines as an object, it allows me to create the cropped area and and click the OK button to create the cropped surface in a separate drawing called EGL-Cropped Stages. When I open EGL-Cropped Stages, the prospector shows a TIN surface has been created but the Properties>Definitions Tab is empty and no surface appears.

To get around this I've recreated EGL as a TIN surface and added a data clip boundary which encompasses all three stages, then added the DEM file. Then cropped from this successfully. Wondering if anyone has experienced the issues above or has any comments regarding advantages of cropping from a surface created as a grid surface or a TIN surface. I have attached the dwg but the tif file is too big.

Any comments would be appreciated.

Cheers,

[Pointdump]

Hi Oliver,
I don't see any surfaces in your drawing.
You could post a link to your Tiff using DropBox, WeTransfer, etc.
If you MAPEXPORT your area-of-interest polygons out to shapefiles, you can use CloudCompare or QGIS to crop the Tiff.
Dave

[OliverE]

Sorry, I've recreated a test surface that is displaying the same behavior and attached it along with the tif I used.

Thanks,

[Pointdump · Accepted solution]

Hi Oliver,
Thanks for posting your data and drawing.
I got same as you when I tried to Create a Cropped Surface. Type and OK were greyed out. Double-clicking some of the entry lines in that dialogue box were exasperating dead ends. So I gotta say it doesn't seem possible to Create Cropped Surface with a Grid Surface.
Data Clipping Boundary works as well with a Grid Surface as with a TIN Surface, but it looks like the TIN Surface is the only way to go with what you want to do.
Dave

[Neilw_05]

Hi Dave, I see you are using CloudCompare too. It is my go to for converting or extracting data from large point clouds. Did you know it can read dxf files too? Not to say it is better than exporting to shape, but maybe.

[Pointdump]

Hi Neil,
I learned about CloudCompare from you. I did not know it could also read DXF files. Good to know.
Dave

[OliverE]

Thanks for looking into it. Does anyone know the reason why you can't crop a grid surface? What are the other restrictions when using a grid surface? It doesn't seem like the Simplify command works on a grid surface either.

Cheers.