I want to count trees in SAGA GIS and I am trying to follow the steps described in Counting trees using segmentation and vectorization in SAGA Gis from dominoc925.blogspot.com (05th, March, 2012).

The problem is while I was able to convert the las file into an .asc DEM, I could not retrieve the .asc DSM from the las file. Hence, I can't accomplish step 1 in the workflow above, because I need to import the DSM in SAGA.

How can I convert a las file into DSM?

  • Hi Zia, I'm not understanding your requirement. Are you saying you have a DEM/DSM and want to convert that to Esri ASCII image? – Michael Stimson Aug 27 '14 at 2:01
  • sory,,i have las file...that i have separted between dsm and dem... – Zia Aug 27 '14 at 2:04
  • You have converted your LAS to DSM (surface) and DEM (ground) and want to convert them into ASCII image - is that right? Or do you want to know how to make the LAS file into raster? – Michael Stimson Aug 27 '14 at 2:06
  • yes............. – Zia Aug 27 '14 at 2:08
  • I don't see how this is a duplicate if someone is following a procedure specifically in saga. – johanvdw Aug 28 '14 at 19:01

To convert LAS into DEM / DSM I would recommend LAStools, specifically LAS2DEM, which is free to use for non-commercial use and not that expensive for professional use.

To convert DEM/DSM images into ASCII I use GDAL_Translate with AAIGRID driver or the QGIS raster save as

In ArcGis:

Convert your ground and model key points to MultiPoint using LAS to Multi Point (class codes 2 and 8 in the ASPRS spec) then do the same for your trees (low veg = 3, medium = 4 and high = 5), you might want to skip the low vegetation as it's probably noise.

To create a DEM from your multipoint make a terrain and import your ground/model key multipoints.

To make your tree DSM use Point to Raster with the shape.z as the source, this will not give complete coverage - but that's ok, there isn't trees everywhere.

Alternately you can create a LAS Dataset and filter the codes you are interested in, then use LAS Dataset to Raster to create your raster(s)... use TRIANGULATION for your DEM and BINNING (Cell Assignment Type = MAXIMUM) for your tree raster.

From here you can use IsNull on the tree raster to create a binary raster showing were trees are (and aren't) or Diff to calculate the tree height above the surface.

  • Do you have software other than Saga? ArcGis can do this with helpful user interfaces but if you don't already have it... – Michael Stimson Aug 27 '14 at 2:40
  • Yes, i do...i converted to multilaspoint then topo raster... there was a error message... id contur 5.999999600000004 "470500 144000 471999.999 145499.999 perhaps..i think, i have to erase that id, I'm not familiar with las file.. – Zia Aug 27 '14 at 3:03
  • I don't think the GUI is significantly better in ArcGIS. SAGA's GUI is good enough and it also has detailed description about the tools (at least in most cases). Go with the open source if you have a choice and its doable. Those methods are available to everyone. – reima Aug 27 '14 at 3:46
  • I agree @reima, open source is a good common ground. I cannot comment on Saga but having done this in ArcGis it's not that difficult - just a few individual tools. – Michael Stimson Aug 27 '14 at 3:50

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