Removing vegetation seems like a harder problem than buildings. Buildings generally have cuboids and other standard shapes, but how do you determine the difference between small trees, big trees, bracken etc?
It the Scotland we have heather that can coat hills but I’m not sure that you’d be able to tell the difference between that and a forest canopy to assume a height and then subtract. Maybe there’s more than the point cloud to work with.
A raw point cloud is run through a series of processing steps to label each point with a class, e.g. "Ground", "Low/Medium/High Vegetation", "Building", "Transmission Tower", etc.
There will be a different algorithm for each feature class. For example, points that are part of a building might be identified by finding groups of points that form a very flat surface. ML models can also do this based on training data.
The final digital elevation model (DEM) is then just taking the "Ground" class from the classified point cloud and using them to triangulate a surface. This differs from a digital surface model (DSM), which will triangulate a surface based on ground+building+vegetation points.
The description confused me, as it describes the use of a real Lidar measurements to detect "change" in the terrain. But certainly, it can't be a temporal change before and after... to detect medieval settings in the data. Is the area still changing differentlybetween scans over multi year's? I don't think so.
I think this is visualization code highlighting natural VS. human train structures, at known locations of old settlements? Showing different approaches on how to visualize the man-made heights in the terrain.
But still, I'm lost how this could help finding new ones..
I think the examples should make it more clear. Thanks to the high resolution of the data, you can see subtle changes in the slope (aka relief aka microtopography) that could hint to underlying remains of human settlements (usually some suspicious geometric patterns that you would not expect in a natural terrain).
I understand how vegetation could be removed, but buildings? How is that accomplished?
It the Scotland we have heather that can coat hills but I’m not sure that you’d be able to tell the difference between that and a forest canopy to assume a height and then subtract. Maybe there’s more than the point cloud to work with.
https://desktop.arcgis.com/en/arcmap/latest/manage-data/las-...
There will be a different algorithm for each feature class. For example, points that are part of a building might be identified by finding groups of points that form a very flat surface. ML models can also do this based on training data.
https://pro.arcgis.com/en/pro-app/latest/tool-reference/3d-a...
The final digital elevation model (DEM) is then just taking the "Ground" class from the classified point cloud and using them to triangulate a surface. This differs from a digital surface model (DSM), which will triangulate a surface based on ground+building+vegetation points.
The description confused me, as it describes the use of a real Lidar measurements to detect "change" in the terrain. But certainly, it can't be a temporal change before and after... to detect medieval settings in the data. Is the area still changing differentlybetween scans over multi year's? I don't think so.
I think this is visualization code highlighting natural VS. human train structures, at known locations of old settlements? Showing different approaches on how to visualize the man-made heights in the terrain.
But still, I'm lost how this could help finding new ones..
See also here for an in-depth discussion on the potential use of such data: https://www.mdpi.com/2072-4292/15/6/1569
How do you suggest to change the description to make it less confusing?
Of course, nothing so exciting to be discovered in Switzerland anymore ;)