Hi Wesley,

It is unclear to me if you want to aggregate points to distinguish 
individual tree, or if you want to locate the treetops ?

Anyway, I suggest you first use your grid to locate treetops (using 
maximum value as you said), then clustering using the treetops. Is your 
plantation dense ? because if the crowns are touching each other, I 
think it will be pretty hard to cluster them using only points. If you 
have treetops, you can aggregate points around individuals treetops.

To get maximum values, maybe sp::overlay can get you started, but I 
think it is more to get grid value to point than reverse. I do it in 
ArcGIS, but I would be happy to have a solution in R if you find one.

Etienne

Wesley Roberts a écrit :
> Dear R-sig-Geo,
>
> I am currently looking at clustering a LiDAR point cloud (trees in a plantation forest) using R and have some questions that I hope some of you may be able to answer. 
>
> My method is a two stage approach, firstly I selected potential tree locations by overlaying a static grid on the point data and selecting the maximum value within each grid. These locations were stored as potential tree locations and have been used as sample data in a spatial clustering approach (I would have liked to use a moving filter but could not find a local maximum approach implemented in R). These points and the original data are now being clustered using the clus algorithm in the spatclus package.
>
> My query regards the use of an algorithm developed for disease mapping (Kuldorff's circular zone in 2D) with Lidar data. The density of the lidar points is around 5 per square meter and I am concerned that the algorithm will not be able to identify clusters based on height. I am yet to inspect the results as the clus algorithm is still running so I cant comment on that right now, but I was wondering if anyone on the list had any suggestions wrt the clustering and or segmentation of lidar point clouds using R. I am unwilling to use interpolation as I want to avoid the lengthy process of selecting the correct interpolation procedure and or model and would like to stick with the point cloud.
>
> Any advice on this matter would be greatly appreciated.
> Many thanks and kind regards,
>
> Wesley
>
>
> Wesley Roberts MSc.
> Researcher: Earth Observation
> Natural Resources & the Environment (NRE)
> CSIR
> Tel: +27 (0)21 888-2490
> Fax: +27 (0)21 888-2693
> "To know the road ahead, ask those coming back."
> - Chinese proverb
>
>
>
>   

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