How to import ASC points into boundary

[Liesl_H]

Hello,

I have a very large set of elevation data (for the entire city of Calgary) in ASC format and my computer crashes when I try to import all of it. I have tried creating a boundary but CAD wants the surface FIRST, which kind of defeats the purpose. Is there a way to predetermine the area you want to import into?

AutoCAD Civil 3D 2020

Thanks in advance,

Liesl

[v-silvestre]

Hi @Liesl_H, you could try creating a surface, then adding a boundary definition before importing the ASC file.  I haven't tried it myself, but I'm wondering if it might help.  Any chance you could post the ASC file?

[rl_jackson]

Try adding the point file to the surface instead of adding the points to the drawing.

[ChicagoLooper]

Hi @Liesl_H

Wow! Entire city. That's huge, I mean huuuuuge. 😊

How big is your ASC file?

Over 1 gig? Over 2 gig? 3? 4?

Just curious. 

[TerryDotson]

Here is something definitely worth trying.

1. Use TXT2LAS in LASTOOLS from the late great Martin Isenburg to create a .LAZ (Lidar) file.
2. Use the DotSoft LidarTools Freeware on Autodesk App Store, you will be able to pick a rectangular area to limit the points and create a Civil3D TinSurface.

[rl_jackson]

@ChicagoLooper ,

Guess I should have read the parathesis 😄 Wow @Liesl_H that is a lot of data. You'll need to clip that as anything about a G or so becomes unusable IMO, less is better.

[Pointdump]

Hi Liesl,
I like Terry's @TerryDotson idea of using TXT2LAS and then his LidarTools.
You can add a Data Clip Boundary to your Surface Definition before adding the ASC points.
You can also crop the points to your Area of Interest beforehand in QGIS or CloudCompare.
Dave

[Pointdump]

Wow, 4.2GB! That's insane. >>>Link<<<. Why didn't they break that up into tiles? Even QGIS chokes on that much data. It took almost 5 minutes to bring it in.

Dave

[Pointdump]

306,687,994 Points! I can't get TXT2LAS to recognize the ESRI ASC file format. CloudCompare can read it and re-save to LAS format. LAS2LAS takes the 5.9GB LAS file and re-saves to a 410MB LAZ file. WeTransfer link >>>Here<<<.
Dave

[Pointdump]

Liesl,
Any way you look at it you'll need 3rd party software. When I run the 410MB LAZ file through ReCap I get a 6+GB file that chokes Civil 3D. So the 2 best options are Terry's LidarTools or cropping the LAZ file in CloudCompare with a shapefile of your Area of Interest.
Dave

[ChicagoLooper]

FYI,

ASC format is a grid—not points—like tif or DEM. It’s a raster and you could, IF the file size was manageable, add it to modelspace using an FDO connection. 

[ChicagoLooper · Accepted solution]

Hi @Liesl_H 

Image-1: Here's the Calgary asc in another program, Global Mapper. The downloaded acs is 4.18 GBs. It took about 60 seconds to add two files: the acs and the topo map. To crop, I drew a tiny red rectangle in the middle and used it as the cropping edge. It demarcates the 'area' I want to keep. 

Image-1

Image-2: Back in AutoCAD, I add the newly cropped asc to modelspace (FDO connection) and it looks like this. At this point I could delete the asc from the drawing since I no longer need it. Instead of deleting though, I un-check the asc from the Map Task Pane. 

Image-2

Image-3: I can create a surface using the same cropped asc as the surface definition.

Image-3

Image-4: Here's the surface with the contours turned OFF. It's using a surface style that displays just the triangles. You can clearly see a square pattern with diagonals running through each square. This is because ASC format is a grid consisting of pixels and you could say each pixel color represents elevation. The surface isn't generated by 'elevated points' where the elevation is based on the point's z-value. If it was you'd see triangulation, not squares & diagonals.

<<The big white roof left of center is the IKEA Store. The Bow River is on the right.>>

Image-4

Image-5: Here's the same surface with the triangles turned OFF and the contours turned ON.

Image-5

Image-6: Here's the same asc but with a larger cropped area compared to the one shown in image-2. It extends farther in all directions, i.e. north, south, east and west. This cropped asc is 67,998 MB.

Image-6

Image-7: This is the same cropped asc as image-2. It's only 2,633 MB. For comparison, and as stated in image-1, the original downloaded asc is a whopping 4.18 GBs. 

Image-7

Too bad AutoCAD chokes. It just can't handle large files easily. If it could we wouldn't get calluses pressing CNTL+ATL+DEL and all of us would be happier.

[Liesl_H]

This is exactly what I needed. Thank you to you and everyone who responded to this question. I could not do my work without this group of people!!

"If it could we wouldn't get calluses pressing CNTL+ATL+DEL and all of us would be happier."   Indeed!

Liesl