rGEDI (version 0.1.11)

gediWFSimulator: GEDI full waveform data simulation

Description

Simulate GEDI full waveform data from Airborne Laser Scanning (ALS) 3D point cloud

Input and output filenames, and formats

Usage

gediWFSimulator(
  input,
  output,
  waveID = NULL,
  coords = NULL,
  listCoord = NULL,
  gridBound = NULL,
  gridStep = 30,
  pSigma = -1,
  pFWHM = 15,
  readPulse = NULL,
  fSigma = 5.5,
  wavefront = NULL,
  res = 0.15,
  topHat = FALSE,
  sideLobe = FALSE,
  lobeAng = 0,
  checkCover = FALSE,
  maxScanAng = 1e+06,
  decimate = 1,
  pBuff = as.integer(2e+08),
  maxBins = as.integer(1024),
  countOnly = FALSE,
  pulseAfter = FALSE,
  pulseBefore = TRUE,
  noNorm = FALSE,
  noOctree = FALSE,
  octLevels = as.integer(0),
  nOctPix = as.integer(40),
  keepOld = FALSE,
  useShadow = FALSE,
  polyGround = FALSE
)

Arguments

input

character vector. lasfile input filename

output

character. output filename

waveID

id. supply a waveID to pass to the output (only for single footprints) Single footprint, list of footprints, or grid of footprints

coords

lon lat numeric vector. footprint coordinate in same system as lasfile

listCoord

name. Text file with list of coordinates. Pattern: X Y `[waveID]` `[geoCoordsX]` `[geoCoordsY]`. `[]` are optional, separated by spaces.

gridBound

minX maxX minY maxY numeric vector. make a grid of waveforms in this box

gridStep

res. grid step size Lidar characteristics. Defaults are expected GEDI values.

pSigma

pSigmasig. set Gaussian pulse width as 1 sigma

pFWHM

fhwm. set Gaussian pulse width as FWHM in ns

readPulse

file. read pulse shape and width from a file insteda of making Gaussian

fSigma

sig. set footprint width

wavefront

file. read wavefront shape from file instead of setting Gaussian. Note that footprint width is still set by fSigma

res

res. range resolution of waveform digitisation to output, in units of ALS data

topHat

use a top hat wavefront

sideLobe

use side lobes

lobeAng

ang. lobe axis azimuth Input data quality filters

checkCover

check that the footprint is covered by ALS data. Do not output if not

maxScanAng

ang. maximum scan angle, degrees

decimate

x. probability of accepting an ALS beam Computational speed options

pBuff

s. point reading buffer size in Gbytes

maxBins

for HDF5, limiting number of bins to save trimming.

countOnly

only use count method

pulseAfter

apply the pulse smoothing after binning for computational speed, at the risk of aliasing (default)

pulseBefore

apply the pulse smoothing before binning to avoid the risk of aliasing, at the expense of computational speed

noNorm

don't normalise for ALS density Octree

noOctree

do not use an octree

octLevels

n. number of octree levels to use

nOctPix

n. number of octree pixels along a side for the top level Using full waveform input data (not tested)

keepOld

do not overwrite old files, if they exist

useShadow

account for shadowing in discrete return data through voxelization

polyGround

find mean ground elevation and slope through fitting a polynomial

#'

Value

Returns an S4 object of class hdf5r::H5File form the hdf5r package containing the simulated GEDI full-waveform.

See Also

i) Hancock, S., Armston, J., Hofton, M., Sun, X., Tang, H., Duncanson, L.I., Kellner, J.R. and Dubayah, R., 2019. The GEDI simulator: A large-footprint waveform lidar simulator for calibration and validation of spaceborne missions. Earth and Space Science. https://doi.org/10.1029/2018EA000506

ii) gediSimulator: https://bitbucket.org/StevenHancock/gedisimulator/src/master/

Examples

# NOT RUN {
libsAvailable = require(lidR) && require(plot3D)
if (libsAvailable) {
outdir=tempdir()

# specify the path to ALS data (zip)
alsfile_Amazon_zip <- system.file("extdata", "Amazon.zip", package="rGEDI")
alsfile_Savanna_zip <- system.file("extdata", "Savanna.zip", package="rGEDI")

# Unzipping ALS data
alsfile_Amazon_filepath <- unzip(alsfile_Amazon_zip,exdir = outdir)
alsfile_Savanna_filepath <- unzip(alsfile_Savanna_zip,exdir = outdir)

# Reading and plot ALS file (las file)
als_Amazon<-readLAS(alsfile_Amazon_filepath)
als_Savanna<-readLAS(alsfile_Savanna_filepath)

# Extracting plot center geolocations
xcenter_Amazon = mean(als_Amazon@bbox[1,])
ycenter_Amazon = mean(als_Amazon@bbox[2,])
xcenter_Savanna = mean(als_Savanna@bbox[1,])
ycenter_Savanna = mean(als_Savanna@bbox[2,])

# Simulating GEDI full waveform
wf_Amazon<-gediWFSimulator(input=alsfile_Amazon_filepath,
                          output=file.path(outdir,"gediWF_amazon_simulation.h5"),
                          coords = c(xcenter_Amazon, ycenter_Amazon))

wf_Savanna<-gediWFSimulator(input=alsfile_Savanna_filepath,
                           output=file.path(outdir,"gediWF_Savanna_simulation.h5"),
                           coords = c(xcenter_Savanna, ycenter_Savanna))

# Plot ALS and GEDI simulated full waveform

oldpar<-par()
par(mfrow=c(2,2), mar=c(4,4,0,0), oma=c(0,0,1,1),cex.axis = 1.2)
scatter3D(
         als_Amazon@data$X,als_Amazon@data$Y,als_Amazon@data$Z,
         pch = 16,colkey = FALSE, main="",
         cex = 0.5,bty = "u",col.panel ="gray90",
         phi = 30,alpha=1,theta=45,col.grid = "gray50",
         xlab="UTM Easting (m)", ylab="UTM Northing (m)", zlab="Elevation (m)")

plot(wf_Amazon, relative=TRUE, polygon=TRUE, type="l", lwd=2, col="forestgreen",
    xlab="", ylab="Elevation (m)", ylim=c(90,140))
grid()
scatter3D(
         als_Savanna@data$X,als_Savanna@data$Y,als_Savanna@data$Z,
         pch = 16,colkey = FALSE, main="",
         cex = 0.5,bty = "u",col.panel ="gray90",
         phi = 30,alpha=1,theta=45,col.grid = "gray50",
         xlab="UTM Easting (m)", ylab="UTM Northing (m)", zlab="Elevation (m)")

plot(wf_Savanna, relative=TRUE, polygon=TRUE, type="l", lwd=2, col="green",
    xlab="Waveform Amplitude (%)", ylab="Elevation (m)", ylim=c(815,835))
grid()

par(oldpar)

close(wf_Amazon)
close(wf_Savanna)
}

# }