Exported Point cloud LAS file classification of data


#1

Hi All
This is my first time on the DD forum. I have a question regarding point cloud data.
I have 17 site along the Western Australian coast to fly and process for a Government Departmnet.
I have completed 6 and processed all of the maps along with the GCPs. With GPS RTK I manually recorded the centre of all tracks in the area. This was a good check on my elevation data the results are very very good.
The problem I have is that I need to process the data without any ground cover, so the client requires a 2m grid of the area with only the ground points and no vegetation.
The area is covered in a lot of small and medium clumps of bush and white beach sand.
I am using Global Mapper to process the data and finding it very difficult to get the end product.

How do I just end up with the ground points then i can process the contours?


#2

Hi @platinum_surveys,

Typically data for the ground points (also called bare-earth) is collected with a LiDAR mapping system. The laser finds spots between the vegetation to reach a lower level (hopefully the earth), and, when the data is processed, the lowest elevation found is used to make a 3D model. But this may not fit in your budget.

Another way is to use an App from the DroneDepoy collection that allegedly removes vegetation. I have not tried this App so I do not know how well it works. It seems like your case might give good results as you only have small plants to remove and lots of exposed sand. The App is call Digital Terrain Model which costs $19.99 per map.

A third approach is to export the 3D model from DroneDeploy and put contours on that. In my experience the DroneDeploy 3D model does not capture much detail associated with small plants so your contour lines may look fine. I import the 3D model into Rhino and then use a Python script with a nice GUI interface to generate 3D contour maps (which can be looked at in 2D of course). Here is an example with 1’ contour lines:

There are more than 100 small plants around the building but they do not show up in the contours much. Only the really big 6’ tall plants show up very well. Contour lines in metric units could also be generated. Here is the same contour map with 25 cm contour lines:

Regards,
Terry.


#3

Hi Terry
Thank you for your email response, it is much appreciated. I will try Digital Terrain Model.
I will also try the 3D export out of Drone-deploy. I can generate the contour with 12D survey software with out any problems. It is getting the correct ground points which I am struggling with.
I have purchased Global Mapper Lidar model, I am having some problems classifying the data so I just end up with just the ground points.


#4

Hi Terry

I starting using the App Digital Terrain Model, they sent me a DTM shape fill which I had trouble opening in a Cad package.
I purchased a software package called Arcv2Cad 7.0 which works very well now i can export a DXF for the DTM sent to me by Digital Terrain Model. I have processed the data for the client I require in 12D survey software.
Thank you for your help