pc_2D_mdtm: Create a Digital Terrain Model from UAV generated point...

In uavRst: Unmanned Aerial Vehicle Remote Sensing Tools

Description

Create a Digital Terrain Model from a high density point cloud as typically derived by an optical UAV retrieval. Due to the poor estimation of ground points a minimum samopling approach is applied. It retrieves on analyzing multiple sampling resolutions gridsizes the ground minimum values and interpolates on these samples a surface grid with a higher target resolution. this is a kind of an try and error process and provides fairly good results if the point cloud shows at least some real surface points on a not to coarse grid.

Usage

pc_2D_mdtm(
  laspcFile = NULL,
  gisdbasePath = NULL,
  grassVersion = 1,
  searchPath = NULL,
  tension = 20,
  sampleMethod = "min",
  cutExtent = NULL,
  sampleGridSize = c(100, 50, 25),
  sw_range = 0.2,
  targetGridSize = 0.1,
  splineThresGridSize = 0.5,
  projFolder = NULL,
  proj4 = "+proj=utm +zone=32 +datum=WGS84 +units=m +no_defs +ellps=WGS84",
  giLinks = giLinks,
  verbose = FALSE
)

Arguments

laspcFile	character. default is NULL path to the laz/las file(s)
gisdbasePath	character. default is NULL root directory of the project. NOTE the function creates two subfolder named run and output
grassVersion	numeric. version of GRASS as derived by findGRASS() default is 1 (=oldest/only version) please note GRASS version later than 7.4 is not working with r.inlidar
searchPath	path to look for grass
tension	numeric. tension of spline interpolation.
sampleMethod	character. sampling method of r.in.lidar Statistic to use for raster values Options: n, min, max, range, sum, mean, stddev, variance, coeff_var, median, percentile, skewness, trimmean Default: mean
cutExtent	clip area
sampleGridSize	list of integer values for the chooses moving window resolution for optimize Ground model default is c(150,50,5)
sw_range	numeric multiplicator for the accepted percentage difference of two search windows height values range typically [0,1] . Example z value of sampleGridSize[100] - sampleGridSize[50] = 50 => 50 *0.2 = 10. So 10 meters are acceped as a valid value.
targetGridSize	numeric. the resolution of the target DTM raster
splineThresGridSize	numeric. threshold of minimum gridsize tha is used for splininterpolation if the desired resolution is finer a two step approximation is choosen first step spline interpolation using the treshold gridsize second step bilinear resampling to the desired targetGridSize.
projFolder	subfolders that will be created/linked for R related GRASS processing
proj4	character. valid proj4 string that should be assumingly the correct one
giLinks	list of link2GI cli pathes, default is NULL
verbose	to be quiet (1)

Value

Digital Terrain Model from UAV generated point clouds as raster* object

Author(s)

Chris Reudenbach, Finn Möller

Examples

## Not run: 

require(uavRst)
require(link2GI)

# create and check the links to the GI software
giLinks<-list()
giLinks$grass<-link2GI::linkGRASS7(returnPaths = TRUE)
if (giLinks$grass$exist) {

# get the data
utils::download.file(url="https://github.com/gisma/gismaData/raw/master/uavRst/data/lidar.las",
                     destfile="lasdata.las")

# create 2D point cloud DTM
dtm3 <- pc_2D_mdtm(laspcFile = "lasdata.las",
                   gisdbasePath = tempdir(),
                   tension = 20 ,
                   targetGridSize = 0.5,
                   sampleGridSize = c(100, 50, 25),
                   giLinks = giLinks)
 raster::plot(dtm3)
}

## End(Not run)

uavRst documentation built on Dec. 30, 2019, 5:06 p.m.