皆さん、こんにちは、私はArcGISを使い始めたばかりで、現在修士課程のプロジェクトとしてLiDARデータを用いて都市林の炭素貯蔵量の変化を特定するために樹木を抽出しようとしています。派生した正規化DSMから小さな植生を除去するために、高さが3m未満のピクセルを除去する条件関数を適用しました。問題は、結果のラスター層で樹木と建物を区別する方法が見つからないことです。残念ながら、元のLASデータでクラスコードが誤って割り当てられており、すべてが植生として分類されているため、コードを使って植生を抽出できませんでした。 LiDARデータやDSMだけを使って植生を抽出する他の方法はありますか？どんな助けでも大変ありがたいです！ありがとうございますジョニー

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LiDARおよび派生DSMからの樹木抽出

JonnyWilks

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皆さん、こんにちは、<\/P>

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私はArcGISを使い始めたばかりで、現在修士課程のプロジェクトとしてLiDARデータを用いて都市林の炭素貯蔵量の変化を特定するために樹木を抽出しようとしています。派生した正規化DSMから小さな植生を除去するために、高さが3m未満のピクセルを除去する条件関数を適用しました。<\/P>

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問題は、結果のラスター層で樹木と建物を区別する方法が見つからないことです。残念ながら、元のLASデータでクラスコードが誤って割り当てられており、すべてが植生として分類されているため、コードを使って植生を抽出できませんでした。<\/P>

<\/P>

LiDARデータやDSMだけを使って植生を抽出する他の方法はありますか？どんな助けでも大変ありがたいです！<\/P>

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ありがとうございます<\/P>

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ジョニー<\/P><\/BODY><\/HTML>

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IanMurray

Have a look at this blog, should help get you started.

https://community.esri.com/people/acrawford-esristaff/blog/2016/12/22/arthurs-feature-extraction-from-lidar-dems-and-imagery

Also, does your .las files have intensity values? That is another way to help distinguish rooftops from natural features.(i.e. trees).

XanderBakker

There is also in ArcGIS Pro the Classify LAS Building—Help | ArcGIS Desktop tool to classify buildings. You could extract the points that remain unclassified (and which are no ground, see Classify LAS Ground—Help | ArcGIS Desktop ) and apply the Classify LAS By Height—Help | ArcGIS Desktop to classify the trees (assuming you don't have electric transmission tower and other objects).

XanderBakker

In addition there is a toolbox called 3D Sample Tools (see https://www.arcgis.com/home/item.html?id=fe221371b77940749ff96e90f2de3d10 ) that I have used to extract trees from LiDAR data and I used that to create a 3D representation of the trees for the 3D distance to overhead power lines. See blog post here:

https://community.esri.com/people/xander_bakker/blog/2016/07/14/calculating-the-3d-distance-of-trees-derived-from-lidar-data-to-overhead-power-lines

JonnyWilks

Thanks for the quick response! I've been able to classify the buildings and ground with the first two tools you mentioned. Following that, how would I extract only the points that remain unclassified in order to run the "Classify LAS By Height" tool?

XanderBakker

The tool will only consider the class code 0 and 1 (Never classified and Unclassified):

ArthurCrawford01

Hello Jonny,

This is the writer of the blog that Ian Murray referenced and developer of the tool to extract tree points. If you are trying to get volume of trees, I would focus on using the Z-Range method option of the LAS Point Statistics As Raster. Here's the link for it:

https://desktop.arcgis.com/en/arcmap/latest/tools/data-management-toolbox/las-point-statistics-as-raster.htm

http://pro.arcgis.com/en/pro-app/tool-reference/data-management/las-point-statistics-as-raster.htm

This will create a DEM showing the distance between first and last return, it's what I use in the tool Ian mentioned.

Tree Volume .

So the area between the red and the light blue I think is what you are trying to get. Once you create the Z-Range using LAS Point Statistics as Raster, you will need to remap the say -100 to 8 foot as no data. The red and dark blue line shows what will be 0 or no data in the raster using LAS Point Statistics as Raster with Z-Range method. This will give you that area as a raster, then you can use the Surface Volume tool with the plane height set to 0.

https://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/surface-volume.htm

Hope this helps,

Arthur Crawford - Esri

Kara_Lara

This is an awesome toolset!!! Thank you!

Fabio_Secanho

Hey Arthur,

I need to estimate trees per acre of an area that I have Lidar data on. I've downloaded your toolbox (Trees From LiDAR) but when I try to open it, I get an error message saying "The tool is not licensed". I have all the necessary licenses and I use ArcGIS Pro 2.7. I don't need to visualize the trees, but only estimate the number of trees per acre. Is this tool appropriated for this task? Any other suggestion on a workflow to accomplish this?

Thank you very much!
Fabio

ArthurCrawford01

Hello Fabio,

It would be good for getting a rough estimate of trees per the acre of a certain size. It will not get the under canopy trees. If you paired it with any detailed tree stand information, it could be used to interpolate the trees in other areas. If Trees from Lidar found 150 trees in an acre and the tree stand (detailed tree inventory) finds 300 trees, you could estimate based on number of trees from Trees from lidar x 2.

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