[GIS] Comparing two Digital Elevation Models (DEMs) from LAS files

arcgis-desktoparcmapdemlidarraster

I have two LiDAR files (.las), one is original let's say with X points. And the other is copy of the first .las file but with Y points, where Y is less than X.

Now, I want to compare the Digital Elevation Models (DEMs) of these two .las files and visualize how different they are.

I want to get information like RMSE, standard deviation, among other types of comparison.

I would appreciate, if anyone could tell me what softwares, and ways to get the comparison info.

Best Answer

How to compare two Digital Elevation Models (DEMs) in R. 

#-------------------------------------------------------------------------
#Creating a reproducible example

library(raster)

  #simulating raster_1

  f = system.file("external/test.grd", package="raster")
  DEM_1 = raster(f)

  #simulating raster_2

  DEM_2 = DEM_1
  # replacing values from raster_1 to create a new raster sample (raster_2)
    DEM_2[(DEM_2>500 & DEM_2<900)] = 550
    DEM_2[(DEM_2>200 & DEM_2<300)] = 500

#-------------------------------------------------------------------------
# Comparison 1 (DEM_3 resulted from subtracting DEM_2 from DEM_1)

  DEM_3 = DEM_1 - DEM_2

    par(mfrow=c(1,3))

    plot(DEM_1, main = "DEM_1")
    plot(DEM_2, main = "DEM_2")
    plot(DEM_3, main = "DEM_3 = DEM_1 - DEM_2")

      dev.off()

enter image description here

#-------------------------------------------------------------------------
#Comparison 2 (histogram)

  hist(DEM_1, prob=T, main="DEM_1", xlab="")
  hist(DEM_2, prob=T, main="DEM_2", xlab="")
  hist(DEM_3, prob=T, main="DEM_3 = DEM_1 - DEM_2", xlab="")

    par(mfrow=c(1,1))

  standard_deviation = sd(c(as.matrix(DEM_3)),na.rm=T)

    dev.off()

enter image description here

#-------------------------------------------------------------------------
#comparison 3 (RMSE)

  library(hydroGOF)

  DEM_1_matrix = c(as.matrix(DEM_1))
  DEM_2_matrix = c(as.matrix(DEM_2))

  rmse = rmse(DEM_1_matrix,DEM_2_matrix)
  rmse
  [1] 135.3675 # this is the root mean squared error (RMSE) result.

See @whuber's answer on Comparing two TINs created using ArcGIS for Desktop? for a theoretical insight about this issue.

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