Calculation of pulse, point density off?

[Silviculturalist]

Is it expected that the calculation of the pulse, point density / m**2 does not align with the manual calculation?

library(lidR)
LASfile = system.file("extdata","example.laz",package='rlas')
las = readLAS(LASfile)
las = retrieve_pulses(las)
summary(las)

my_metrics <- function(pulseID)
{
  return(list(nPulses = length(unique(pulseID))))
}

result = cloud_metrics(las,~my_metrics(pulseID))
result$nPulses/area(las)

summary(las) provides pulse density as 2.63 pulses/m2 whereas manual calculation gives 2.83?

[Jean-Romain]

The summary looks only at pre-computed number of first return while retrieve_pulse used the gpstime attribute in order to compute the exact pulse ID of each point. This way if you have a 2nd or 3rd return only without the first one (e.g. on the edge of the dataset) you still get a pulse.

The difference should be minimal in most cases but here you chose an extraordinary tiny dataset (30 points) where a single point difference can change a lot the final value.

[Silviculturalist]

Yes, difference is minimal, noticed some decimal differences on my real dataset. Small dataset here only as reprex. Maybe it can be clarified in your documentation for summary function ?

Something like - # pulses, first return only?