gediWFSimulator: GEDI full waveform data simulation

In rGEDI: NASA's Global Ecosystem Dynamics Investigation (GEDI) Data Visualization and Processing

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

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)
}

rGEDI documentation built on Jan. 19, 2021, 3:01 p.m.