# Insitu sampling took place within 40m x 40m square plots, so you use a 20m radius. Source: Colin Williams, NEON Extract Plot Data Using Circle: 20m Radius Plots In this case, you will tell R to extract the maximum value of all pixels using the fun=max command. Values for all pixels in the specified raster that fall within the circular buffer are extracted. The extract function in R allows you to specify a circular buffer radius around an x,y point location. If your plots are circular, then you can use the extract() function. There are a few ways to go about this task. You will then extract all CHM pixels that fall within the plot boundary to use to estimate tree height for that plot. Next, you will create a boundary region (called a buffer) representing the spatial extent of each plot (where trees were measured). 9 )) # pch 0 = square plot ( SJER_plots, pch = 16, cex = 2, col = 2, add = TRUE )Įxtract CMH Data Within 20m Radius of Each Plot Centroid # import plot centroids SJER_plots <- readOGR ( "data/week-04/california/SJER/vector_data/SJER_plot_centroids.shp" ) # OGR data source with driver: ESRI Shapefile # Source: "/root/earth-analytics/data/week-04/california/SJER/vector_data/SJER_plot_centroids.shp", layer: "SJER_plot_centroids" # with 18 features # It has 5 fields # Overlay the centroid points and the stem locations on the CHM plot plot ( SJER_chm, main = "SJER Plot Locations", col = lors ( 100, start =.
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