openSTARS (version 1.2.3)

calc_attributes_sites_exact: Calculate attributes of the sites.

Description

For each site (observation or prediction) the total catchment area is calculated ('H2OArea'). Additionally, other attributes (predictor variables) can be derived based on given raster or vector maps. This function calculates exact values for catchments derived with r.stream.basins and can take considerable time if there are many sites. Catchment raster maps can optionally be stored as "sitename_catchm_X" (X = locID).

Usage

calc_attributes_sites_exact(
  sites_map = "sites",
  input_raster = NULL,
  stat_rast = NULL,
  attr_name_rast = NULL,
  input_vector = NULL,
  stat_vect = NULL,
  attr_name_vect = NULL,
  round_dig = 2,
  calc_basin_area = TRUE,
  keep_basins = FALSE,
  overwrite = FALSE
)

Arguments

sites_map

character; name of the sites (observation or prediction) attributes shall be calculated for. "sites" (default) refers to the observation sites.

input_raster

character vector (optional); name of additional raster maps to calculate attributes from.

stat_rast

character vector (optional); statistics to be calculated, one of: "min", "max", "mean", "stddev", "variance", "sum", "median", "percent", "area" or "percentile_X" (where X gives the desired percentile e.g. 25 for the first). Must be provided if input_raster are given.

attr_name_rast

character vector (optional); column name for the attributes to be calculated. Attribute names must not be longer than 10 characters. Must be provided if input_raster are given.

input_vector

character string vector (optional); name of additional vector maps to calculate attributes from.

stat_vect

character string vector (optional); statistics to be calculated, one of: "percent", "area" or "count." Must be provided if input_vector is given.

attr_name_vect

character string vector (optional); column name(s) in the vector file provided to calculate the attributes from (if input_vector is a polygon map and stat_vect is "percent") or giving the new name attributes to calculate (if input_vector is a point map and stat_vect is "count". Must be provided if input_vector is given.

round_dig

integer; number of digits to round results to. Can be a vector of different values or just one value for all attributes.

calc_basin_area

boolean; shall the catchment area be calculated? (Useful to set to FALSE if the function has been called before with keep_basins = TRUE.)

keep_basins

boolean; shall raster and vector maps of all the watersheds be kept? Defaults to FALSE.

overwrite

boolean; shall existing columns be overwritten; defaults to FALSE

Value

Nothing. The function appends new columns to the sites_map attribute table

• 'H2OArea': Total watershed area of the watershed upstream of each site.

• attr_name_rast: Additional optional attributes calculated based on input_raster maps.

• attributes form vector maps:Additional optional attributes calculated based on input_vector maps. The column names are based on the unique entries of the column(s) given in attr_name_vect.

Please note that for sampling points that lie in the same DEM raster cell along a stream identical values are calculated because identical watersheds are derived.

Examples

# NOT RUN {
# Initiate and setup GRASS
dem_path <- system.file("extdata", "nc", "elev_ned_30m.tif", package = "openSTARS")
if(.Platform$OS.type == "windows"){
  grass_program_path = "c:/Program Files/GRASS GIS 7.6"
  } else {
  grass_program_path = "/usr/lib/grass78/"
  }

setup_grass_environment(dem = dem_path, 
                        gisBase = grass_program_path,      
                        remove_GISRC = TRUE,
                        override = TRUE
                        )
gmeta()
                        
# Load files into GRASS
dem_path <- system.file("extdata", "nc", "elev_ned_30m.tif", package = "openSTARS")
sites_path <- system.file("extdata", "nc", "sites_nc.shp", package = "openSTARS")
import_data(dem = dem_path, sites = sites_path)

# Derive streams from DEM
derive_streams(burn = 0, accum_threshold = 700, condition = TRUE, clean = TRUE)

# Prepare edges
calc_edges()

# caluclate slope as potential predictor
execGRASS("r.slope.aspect", flags = c("overwrite","quiet"),
          parameters = list(
            elevation = "dem",
            slope = "slope"
          ))
calc_attributes_edges(input_raster = "slope", stat_rast = "max", attr_name_rast = "maxSlo")

# Prepare sites
calc_sites()
calc_attributes_sites_approx(input_attr_name = "maxSlo", output_attr_name = "maxSloA", stat = "max")
calc_attributes_sites_exact(input_raster = "slope", attr_name_rast = "maxSloE", stat_rast = "max")

# Plot data
library(sp)
dem <- readRAST('dem', ignore.stderr = TRUE, plugin = FALSE)
edges <- readVECT('edges', ignore.stderr = TRUE)
sites <- readVECT('sites', ignore.stderr = TRUE)
plot(dem, col = gray(seq(0,1,length.out=20)))
mm <- range(c(edges$maxSlo_e, sites$maxSloA, sites$maxSloE))
b <- seq(from = mm[1], to = mm[2] + diff(mm) * 0.01, length.out = 10)
c_ramp <- colorRampPalette(c("white", "blue", "orange", "red"))
cols <- c_ramp(length(b))[as.numeric(cut(edges$maxSlo_e, breaks = b, right = FALSE))]
# plot stream edges, color depending on maxSlope of the edge
plot(edges,col = cols, lwd = 2, add = TRUE)
cols <- c_ramp(length(b))[as.numeric(cut(sites$maxSloA,breaks = b,right = FALSE))]
# plot sites as points with color corresponding to maxSlop approximate
plot(sites, pch = 19, col = cols, cex = 2, add = TRUE)
cols <- c_ramp(length(b))[as.numeric(cut(sites$maxSloE,breaks = b,right = FALSE))]
#' # plot sites as ring around points with color corresponding to maxSlop exact
plot(sites, pch = 21, bg = cols, cex = 1.1, add = TRUE)
# Some points in the lower centre of the map indicate a difference in max slope between
# approximate and exact calculation (different colors for inner and outer points). However,
# for most points the values are similar
# }