Extraction of diameter at breast height and deadlogs (standing+fallen)

[Bechu K.V. Yadav]

Hi everyone,

Could you please suggest me how can I extract diameter at breast height (DBH) of standing trees. Is it possible to derive volume of dead logs (standing+fallen) using LAStools? I have very high dense point clouds LiDAR data (25-30 points/m2)?

Bechu 

[Terje Mathisen]

What you want is pretty much impossible!

I.e. if you have a lidar scan taken from more or less directly above
said trees, the only thing you might be able to find would be small
voids where there are no ground points, i.e. the horizontal area covered
by the tree.

If the trees are very large (think redwoods here), then your cloud
density would probably be sufficient to generate a model of the internal
volume of each tree, but for normal norwegian spruce/pine/birch forests
you could only be able to estimate each tree volume by using the point
could to locate each individual tree crown, then use the shape of that
crown to determine species and the height would then give you the volume.

This is the approach used for forest monitoring here in Norway at least,
in order to detmine when it should/could be logged.

Re standing dead trees: If those dead trees have lost all their leaves
(or evergreen needles) then the crown model would look quite different
from a live tree, so it should be possible to select them using this
difference.

Fallen trees otoh can be quite obvious!

Terje

-- - <Terje.M...@tmsw.no> "almost all programming can be viewed as
an exercise in caching"

[ramesh.s...@yahoo.com]

I remember one of my friend from forestry mentioning that you can estimate the breast diameter using height and tree canopy diameter given the tree type. This might not be exact calculation but might provide you close enough. Ofcourse fallen trees are different issue....

 

 

Regards,
Ramesh Sridharan
Ph: 505-463-3960
http://www.linkedin.com/in/rameshs

Its only weird if it doesn't work.     

---

From: Bechu K.V. Yadav <bechu...@gmail.com>
To: LAStools - efficient tools for LiDAR processing <last...@googlegroups.com>
Sent: Saturday, September 12, 2015 9:49 PM
Subject: [LAStools] Extraction of diameter at breast height and deadlogs (standing+fallen)

Hi everyone,

Could you please suggest me how can I extract diameter at breast height (DBH) of standing trees. Is it possible to derive volume of dead logs (standing+fallen) using LAStools? I have very high dense point clouds LiDAR data (25-30 points/m2)?

Bechu 

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[vinodk...@gmail.com]

Hi Bechu,

I think Terje and Sridharan  have made the point very clear. I am sharing my own experience. Once I was tempted to measure DBH directly from very dense airborne point cloud (160 points/m2), still  could not find enough points on stem to develop an algorithm to get DBH. However trees could be located and  individual tree point cloud could be extracted. 

Reasons for failure

In large no. of trees, LiDAR points on stem were missing either to define curvature through points (to get girth) or to get diameter end points. Therefore any method cannot be reliable as it will not work for most of the trees

Low Canopy Base Height for some conifers.

First return points are more consistent for structural definition. On stem such points are less. Therefore inconsistent trunk shape

Isolated trees can have better stem returns than in dense forest.

Alternatively, tree height, CPA/CD, CV (Canopy Volume) , species, localised tree density could be found out from Airborne LiDAR. One can develop regression model for biomass/DBH from this. I used tree height, CPA and localised tree density for biomass/carbon estimation.

Terrestrial LiDAR could be used to get DBH or measure volume of dead/dry (standing/fallen) trees. However data collection could be cumbersome and may not be a feasible option.

Regards,

Vinod Kumar

Indian Forest Service

Forest Conservator 

State of Haryana

+919999777671

[Martin Isenburg]

Hello,

In a personal email Bechu had mentioned that he "wants to extract Diameter at Breast Height, canopy gap fraction and deadwood (standing+fallen) found everywhere in the forests using Full Waveform LiDAR data (high point clouds (30points/m2) collected by AusCover (from WARRA reserve site, Tasmania, Australia). Is it possible to locate hollow on eucalyptus trees as hollows are mostly found on deed eucalyptus trees in Tasmanian forests that are useful for birds and beetles?"

For canopy gap fraction you can use lascanopy with the combination of these three options '-cov -gap -fraction' at the desired '-step 10' or so. For the other items ... may it be easier given that the crown of eucalyptus trees is easily penetrated by the 30 pulses per square meter of the airborne full waveform laser? I believe Bechu is talking about the data collected for this project here:

http://www.tern-supersites.net.au/supersites/wrra

And I expected it to be available on the TERN AUScover data server but it is not (yet?) or under a different name?

http://tern-auscover.science.uq.edu.au/thredds/catalog/auscover/field_and_airborne_datasets/airborne/lidar/catalog.html

Regards,

Martin @rapidlasso