coregistration {lidaRtRee}

Tree inventory and canopy height model coregistration

Description

Computes the correlation between the canopy height model and a virtual canopy height model simulated from tree locations, for different translations of tree inventory positions, and outputs the translation corresponding to best estimated co-registration.

Usage

coregistration(chm, trees, mask, buffer = 19, step = 0.5, dm = 2, plot = TRUE)

Arguments

chm

raster. canopy height model

trees

data.frame. the first two columns contain xy coordinates, and the third is the value to correlate to the chm (e.g. tree heights or diameters)

mask

raster. raster mask of tree inventory area

buffer

numeric. radius of the circular buffer area of possible translations

step

numeric. increment step of translations within buffer area to compute correlation values, should be a multiple of raster resolution

dm

numeric. minimum distance between two local maxima in meters

plot

boolean. whether to display the results or not

Value

A list with two elements : first the correlation SpatRaster returned by rasters_moving_cor, second a data.frame returned by raster_local_max

References

Monnet, J.-M. and Mermin, E. 2014. Cross-Correlation of Diameter Measures for the Co-Registration of Forest Inventory Plots with Airborne Laser Scanning Data. Forests 2014, 5(9), 2307-2326, doi:10.3390/f5092307

See Also

rasters_moving_cor, raster_local_max

Examples

# tree inventory
trees <- data.frame(x = c(22.2, 18.3, 18.1), y = c(22.1, 22.7, 18.4), 
z = c(15, 10, 15))

# mask of inventory area
# empty raster with extent
tree_mask <- circle2Raster(20, 20, 9, resolution = 1)
# fill binary mask
tree_mask <- raster_xy_mask(rbind(c(20, 20), c(20, 20)), c(9, 9), tree_mask, 
binary = TRUE)

# simulate chm raster
chm <- terra::rast(extent = c(0, 40, 0, 40), resolution = 1, crs = NA)
xy <- terra::xyFromCell(chm, 1:(ncol(chm) * nrow(chm)))

# add Gaussian surfaces to simulate tree crowns
z1 <- trees$z[1] * exp(-((xy[, 1] - trees$x[1])^2 + (xy[, 2] - trees$y[1])^2 / 2) * trees$z[1] / 50)
z2 <- trees$z[2] * exp(-((xy[, 1] - trees$x[2])^2 + (xy[, 2] - trees$y[2])^2 / 2) * trees$z[2] / 50)
z3 <- trees$z[3] * exp(-((xy[, 1] - trees$x[3])^2 + (xy[, 2] - trees$y[3])^2 / 2) * trees$z[3] / 50)
chm <- terra::rast(cbind(xy, pmax(z1, z2, z3)), type = "xyz") #+rnorm(length(z1),0,1)))

# translate trees
trees$x <- trees$x + 1
trees$y <- trees$y + 2

coreg <- coregistration(chm, trees, mask = tree_mask, buffer = 5, step = 1, dm = 1, plot = FALSE)
coreg$local_max[, c("dx1", "dy1")]

# plot raster
terra::plot(coreg$correlation_raster)
abline(h = 0, lty = 2)
abline(v = 0, lty = 2)
# add location of two local maxima
graphics::points(coreg$local_max[1, c("dx1", "dx2")],
  coreg$local_max[1, c("dy1", "dy2")],
  cex = c(1, 0.5), pch = 3, col = "red"
)