Cropping/Exporting LAS files

Greetings Everybody,

I am beginning the process of 3D printing the Lake Thunderbird watershed using LiDAR (LAS & LAZ) files, and I have some questions regarding cropping and exporting LAS files. First, be advised that I am not a GIS guru by any means. Although I have been importing and exporting spatial data in Civil 3D for years, my only exposure to GIS was in a grad level course years ago. I was planning on using Civil3D for the project but it wasn’t cutting it so I tried, and then bought, Global Mapper with the LiDAR package.

Let me start by providing some background information. I am using data from at least two entities; the City of Norman copied the data to a hard drive for me, and I downloaded the 2018 USGS data from Lidar Explorer. I may be using data from Oklahoma City as well. The data from Norman is segmented based on square-mile sections (Section-Township-Range), which is desirable for printing because I can make each mile-section 3” x 3” (which will just fit my Anycubic Mono 3D-printer) resulting in a watershed model display that will be approximately 5’ x 5.5’.

My problem is that the USGS LAS files are not segmented on the sections, so I have to crop them. This is OK if they cross only section lines, but the problem arises if they cross section lines and the watershed boundary, because I cannot figure out how to crop them twice. I tried cropping to the section and then exporting it to an LAS file, then opening that file and cropping it to the watershed, which gave me the shape I needed, but the detail was lessened considerably.

So, I guess my questions are,

1) Is there a way to crop a layer twice?

2) Barring that, is there a way to export a cropped layer to an LAS (or another format?) file so that it maintains the same detailing as the original LAS file?

I really appreciate any assistance you may provide.

FYI, Here’s a picture of some of my test prints. The land pieces were made using LiDAR data, the lake pieces (these are from Lake Stanley Draper which is in the watershed) using bathymetry DEMs. The elevations for both were scaled up by a factor of two to better show the details.

Cheers!

Russ


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