Spatial heatmap with given value for colour-CodePudding

I built upon this

If you want a filled contour you will have to manually create a matrix covering the area of interest, get the mean population in each bin, convert that into a data frame, then use geom_contour_filled:

z <- tapply(d_pop_be$TOT, list(cut(d_pop_be$E_KOORD, 200), 
                               cut(d_pop_be$N_KOORD, 200)), mean, na.rm = TRUE)

df <- expand.grid(x = seq(min(d_pop_be$E_KOORD), max(d_pop_be$E_KOORD), length = 200),
                  y = seq(min(d_pop_be$N_KOORD), max(d_pop_be$N_KOORD), length = 200))


df$z <- c(tapply(d_pop_be$TOT, list(cut(d_pop_be$E_KOORD, 200), 
                  cut(d_pop_be$N_KOORD, 200)), mean, na.rm = TRUE))

df$z[is.na(df$z)] <- 0

 ggplot(df, aes(x, y))   
 geom_contour_filled(aes(z = z), breaks = c(1, 5, 20, 50, 100, 1000))  
 scale_fill_manual(values = rev(brewer.pal(5, "Spectral")))