Smooth channel profile by removing artifacts

Smooth channel profile by removing artifacts

profile_smooth(distance, elevation, span, radius)

Arguments

distance	distance along channel network (m)
elevation	elevation along channel network (m)
span	span parameter for the loess fit used to detrend the profile (fraction of the total points used for the local fits)
radius	radius of the rolling circle used to smooth the profile (m)

Value

a vector (same length as the inputs) with corrected elevation values along the river

Examples

# get river data
# see DEM processing vignette for example of the extraction of such data from a DEM
data("rivers_cevennes",package = "gtbox")

# get DEM (for plotting)
data("dem_cevennes",package = "gtbox")
dem = rast(dem_cevennes)
rm(dem_cevennes)

df = rivers_cevennes[rivers_cevennes$river==1,] # select a river
df = df[order(df$dist),] # order data according to distance along river
df$area = df$acc*30^2 # compute drainage area
df$chi = profile_chi(df$area,df$dist,aref=1000,mn=0.5) # compute chi
df$z2 = profile_smooth(df$dist,df$z,span=0.1,radius=10e3) # smooth profile
df$z3 = profile_gaussian(df$dist,df$z2,span=0.1,sigma=500) # filter profile
df$gradient = profile_gradient(df$dist,df$z3,window=200) # compute gradient

par(mfrow=c(2,2))
plot(dem)
lines(df$x,df$y,lwd=3,col="blue")
par(mar = c(4,4,0.5,0.5))
plot(df$dist,df$z,type="l",xlab="Distance along river (m)",ylab="Elevation (m)")
lines(df$dist,df$z2,col="firebrick")
lines(df$dist,df$z3,col="dodgerblue")
legend("topleft",c("Raw","Smoothed","Filtered"),lty=1,col=c("black","firebrick","dodgerblue"))
plot(df$dist,df$gradient,type="l",xlab="Distance along river (m)",ylab="Gradient (m/m)")
plot(df$chi,df$z,type="l",xlab="Chi (m)",ylab="Elevation (m)")