national_dem_example.R

library(USAboundaries)
library(sf)
library(dplyr)
library(elevatr)
library(raster)

# Get map of lower 48 states
usa_l48 <- us_boundaries() %>%
  filter(state_abbr != "HI" & 
           state_abbr != "AK" &
           state_abbr != "PR") 
# Get DEM.  Zoom level 4 returns dem of ~ 3.8km resolution for whole of lower 48
usa_l48_dem <- get_elev_raster(as(usa_l48, "Spatial"), src="aws", z = 4, clip = "location")


# Project to albers/meters
usgs_albers <- "+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=37.5 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs"
usa_l48_alb <- usa_l48 %>%
  st_transform(crs = usgs_albers)
usa_l48_dem_alb <- projectRaster(usa_l48_dem, crs = usgs_albers)

# Plot it
plot(usa_l48_dem_alb)
plot(st_geometry(usa_l48_alb), fill = F,  add = T)