Point Cloud Workflow

[jjfuller]

Hey guys, hoping you can help me out with a good workflow for point clouds.  I'll give you a brief rundown of my experience with them to provide a frame of refence.

In 2009 we had the County flown and the company provided us with .las files containg a ground surface.  Because the data was only a ground surface I just indexed the files in C3D, created a surface, and life was good-pretty simple.

Fast forward to present.  We decided not to gather new data as a state agency was doing the entire state and then breaking the data down by county, providing the data for free.  Great!

Now I have the data and a lot has changed.  The .las files are first return broken down by classification.  Also included are .tin files and .dat files.

I've always sidlined ReCap because I didn't really see a need for it; one more step in the import process.  I've played with it a bit so know how to set it up, index files, and bring the files into C3D.

I'm not sure how to filter out unwanted classifications, when I brought the files in directly, they included trees and buildings - things I do not want in my ground surface.  When I bring in a recap file, it seems C3D automaticall filters anything but class 2, but leaves giant holes where groups of trees are situated.

Any advice on how to handle this new data set, ReCap vs C3D indexing, links to articles, posts, videos - basically anything to  help me wrap my dense brain around this would be greatly appreciated!!!

[Anonymous]

When you bring in a drawing to C3D you can filter out classifications for .LAS files. I have attatched a image that includes the area that you would apply the filter. I am not sure how familiar you are with importing .LAS files into C3D so let me know if this is what you are looking for or need help getting to this point!

[jjfuller]

Thanks @Anonymous,  This is what I meant by things have changed a lot.  In 2013 that option was also available in the Insert > Point Cloud > Index on the ribbon (it's been a while since 2013 so my sequence may be a little off).  When using the sequence you attached, my only option is "from drawing object," index new file isn't even there.  I think they removed this command entirely.  The only way I can find to do it through C3D is on the prospector, RC point cloud > Create new.  ReCap seems to be the way of the future but I don't see that it offers a lot of options.  

[Anonymous]

Okay so if you want to use the way I referenced try switching your workspace to "Planning and Analysis" and go to the View tab and open the map task pane. Once that is open click the add data and it will open up add file like I had referenced in my previous post.

I am attatching a walkthrough that my company uses for .LAS and DEM files. You can ignore everything until you get to the inserting into CAD part.

Hopefully this helps you acomplish what you are looking for. 

[autoMick · Accepted solution]

Hi Jon,

You should be able to do it all in Civil3d. It sounds like you'll know many of the steps already, but I'll spell out what I do

- set coordinate system MAPCSASSIGN

- in prospector, right click point clouds and start going through the wizard for point cloud creation

- 1st screen pick a style or create one where the point colour is set by classification

- 2nd screen select your LAS file and cssystem if necessary and create the point cloud.

- When Civil3d has had it's little sleep, zoom to the cloud

So then you should have something like this:

- Right click your point cloud in the prospector and select edit point cloud style

- go to the Classification tab and turn off the categories you don't want (all but 2 Ground)

Check to see if those big gaps where the veg was have any ground strikes. If not try setting the POINTCLOUDPOINTMAX variable to 10 million (the maximum) the display point density to 100 (select the point cloud to get the contextual ribbon) to see if anything else pops up. Otherwise, I guess there just isn't ground data there and  there's not much you can do about it.

To add the filtered data to the a surface, just right click your point cloud in the prospector and select the Add points to surface command. The surface will take the point data as it was when you did that command. It's not dynamic.

Cheers

- Mick

[jjfuller]

SamAV, Thanks for the in depth response! Unfortunately, after 2014 he POINTCLOUDINDEX command has been removed. I tried it in both 2015 and 2016 with no luck. In the newer versions, the options have also been removed from the map task pane. Thanks again for taking a look at this! Kudos

[jjfuller]

@autoMick, Thanks for shedding some light on this.  I was following most of the steps but overlooking a few things like the POINTCLOUDPOINTMAX, and was unsure that the point filters in the style were just for point cloud display or translated to the surface.  This is one of those things that trial and error can eat up days because of "autocad's little sleep," as you put it - still chuckling about that one. 

Running through this now, will report back shortly.

So ReCap, whats the big deal?  I can look at point clouds and make them different colors.  What am I missing?

Thanks again!

[jjfuller]

Thanks to @autoMick and @Anonymous!  Kudos

[Anonymous]

Looks like you found a solution! Just real quick though, the POINTCLOUDINDEX command has been removed. However I use the maptask pane almost weekly in 2015 for adding in point clouds like I showed in that walkthrough... Not sure what you mean by having the option of maptask pane removed, would you mind clarifying it for me?

[jjfuller]

I stand corrected, The option is still accessible in the map task pane in 2015. In 2016, Task Pane>Data>Add Point Cloud Data, the only option I get is "From Drawing Object." Perhaps I have a bad install, could anyone verify in 2016?

[Anonymous]

Can you click create "new index" and then add new file from there under the add point cloud data? 

[jjfuller]

Nope.

[Anonymous]

Interesting! This sounds bad but I am hoping that you have a bad install as this is how my entire company inserts .LAS files and I really dont want to retrain most of them haha!

[jjfuller]

Thanks for all of your help! Sometimes I wonder if upgrading every year is a good idea on not. Look on the bright side, your out in front of it now if they did eliminate indexing from the task pane. If I learn anything else I'll report back. Thanks again!

[autoMick]

@jjfuller thanks glad it helped. Yes it's disconcerting when you can add a point cloud to a surface and not have any real record of what state the pointcloud was in when it was added. It's not real intuitive and prone to mistakes I feel. Imagine having to audit drawings based on a point cloud.

Recap allows you to edit the extents of the point cloud, filter the density (somewhat), delete suspect bits, etc. It also seems to deal with big point clouds better. In truth I don't use it much - I have a nagging feeling that maybe it does more that I think it does... but maybe not.

Cheers

- Mick

[LyleHardin]

Glad I found this thread as I'm doing the same thing and have the same questions. 

We've just downloade .las files from Illinois and I've experimented with two ways of bringing these in.

1. Through the Prospector as described above.

2. Using ReCAP to make a .rcp file, then attach that .rcp file with xref manager.

When making the surfaces, I was surprised to see the ReCap did a better job, seemingly to automatically filter out the trees and buildings and such. But, using the ReCAP method limits what you can do in AutoCAD with the point cloud.

The Prospector method allows you to place different classifications on different layers so you can Freeze points from different classifications.

More options with the Prospector method, but I like the contours from ReCAP better unless I'm doing something wrong with the other method.

[jjfuller]

@LyleHardin, It sounds like I'm battling the same files you are.  We are currently in Madison County, IL(right across from St. Louis) and have historically used our own LiDar.  With the Illinois Height Modernization Program data,  we decided not to collect a new data set this year.  The las files have been made available but include all point classifications.

ReCap is definitely better equipped to handle these large point clouds but lacks the ability to filter based on ASPRS class.  I haven't shared your success with the software filtering the points automatically.  Ideally, ReCap would export an .rcs file containing the filtered out ground points.  C3D plays nicely with recap files and they include all of the points, regardless of visibility.  Thats likely why your contours look better.  C3D does offer the ability to filter Non-Ground points using Planar average or the Kriging interpolation, but this seems completely ridiculous when you have points that are already classified.   

The problem with attaching the las file in prospector is that the point cloud style really just controls visibility.  When zooming out the point cloud density automatically decreases similar to the way LEVELOFDETAIL works on surfaces.  When adding these points to a surface C3D only uses visible points, so if you are zoomed out over a large area and add the points to the surface, it will only add a certain percentage of the points based on the zoom level. 

Below are a few links to other threads concerning this issue.  I plan on hitting the idea station with it this week and will post a link when it's up.

@roskirko came up with the best solution thus far in the first thread.

http://forums.autodesk.com/t5/recap-general-discussion/lidar-classification-can-i-create-an-rcs-file...

http://forums.autodesk.com/t5/autocad-civil-3d-general/point-cloud-classification-use-in-c3d-from-re...

@tcorey and @Vincent_Fredon , you may be interested in the first thread as well.

[LyleHardin]

I used the same .las files with both methods. I think it worked best for me with the .rcp file attached. When making the surface from the attached .rcp, Civil 3D automatically uses only the ground shots. And when I've compared elevations of the contours vs the point clouds, the contours are definitely using the ground shots and ignoring the other classifications just like the command description describes (see image). Plus, I like the way the cloud looks from ReCAP better than the cloud brought in with Prospector.  I've not looked at your links yet but will soon. Thanks for the info!

[jjfuller]

I guess we are just supposed to trust that it's filtering exactly what we want/expect. I would simply rather have direct control over either the points leaving ReCap or the points coming into C3D; and furthermore have the ability to review the properties post-import!

[jjfuller]

@hardin, I still have not successfully attached a recap project with the ground points filtered by class. When using the "create surface from point cloud" option, there are three options in the filtering section of the window - Planar, Kriging, and no filter. When I choose no filter it uses points regardless of class. Kriging produces a ground surface but filters out points if the density is too low in a certain area. For instance a hillside with trees surrounded by fields results in no ground data in that area, even though there are points with a ground classification there. It filters the points mathematically rather than just using the class already assigned to the point.

Could you post the options you are using? I would really like to nail this down!

Thanks,
Jon