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Number and proportion of points by echo types

metrics_echo.Rd

Based on the return number and number of returns, point cloud returns are classified into different echo types. Two different classification routines are applied. Under the first classification routine returns are classified into First, Intermediate, and Last. Under the second classification routine returns are classified into Single or Multiple. Function then calculates point counts and proportions by each echo type. Ratios of Last to First, Intermediate to First, and Multiple to Single, are also calculated.

Usage

metrics_echo(ReturnNumber, NumberOfReturns, z = NULL, zmin = NA)

.metrics_echo

Format

An object of class formula of length 2.

Arguments

ReturnNumber

return number

NumberOfReturns

number of returns

z

Z coordinate of the point cloud (point heights)

zmin

numeric. Minimum z value. If set, z values (heights) below are ignored in calculations.

Value

A list. Calculated metrics include:

  • Number of first (n_first), intermediate (n_intermediate), last (n_last), single (n_single), and multiple (n_multiple) returns

  • Proportion of first (p_first), intermediate (p_intermediate), last (p_last), single (p_single), and multiple (p_multiple) returns

  • Ratio of Last to First (ratio_last_first), Intermediate to First (ratio_intermediate_first), and Multiple to Single (ratio_multiple_single).

Examples

library(lidR)
library(lidRmetrics)
LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
las <- readLAS(LASfile, select = "*", filter = "-keep_random_fraction 0.5")

m1 <- cloud_metrics(las, ~metrics_echo(ReturnNumber=ReturnNumber, NumberOfReturns=NumberOfReturns))

m2 <- pixel_metrics(las, ~metrics_echo(ReturnNumber=ReturnNumber, NumberOfReturns=NumberOfReturns), res = 20)