#' @title Get 800m gridded soil properties from SoilWeb ISSR-800 Web Coverage Service (WCS)
#' @author D.E. Beaudette and A.G. Brown
#' @description Intermediate-scale gridded (800m) soil property and interpretation maps from aggregated SSURGO and STATSGO data. These maps were developed by USDA-NRCS-SPSD staff in collaboration with UCD-LAWR. Originally for educational use and \href{https://casoilresource.lawr.ucdavis.edu/soil-properties/}{interactive thematic maps}, these data are a suitable alternative to gridded STATSGO-derived thematic soil maps. The full size grids can be \href{https://casoilresource.lawr.ucdavis.edu/soil-properties/download.php}{downloaded here}.
#' @param aoi area of interest (AOI) defined using a \code{Spatial*}, \code{RasterLayer}, \code{sf}, \code{sfc} or \code{bbox} object, OR a \code{list}, see details
#' @param var ISSR-800 grid name (case insensitive), see details
#' @param res grid resolution, units of meters. The native resolution of ISSR-800 grids (this WCS) is 800m.
#' @param quiet logical, passed to \code{curl::curl_download} to enable / suppress URL and progress bar for download.
#'
#' @details \code{aoi} should be specified as a \code{SpatRaster}, \code{Spatial*}, \code{RasterLayer}, \code{SpatRaster}/\code{SpatVector}, \code{sf}, \code{sfc}, or \code{bbox} object or a \code{list} containing:
#'
#' \describe{
#' \item{\code{aoi}}{bounding-box specified as (xmin, ymin, xmax, ymax) e.g. c(-114.16, 47.65, -114.08, 47.68)}
#' \item{\code{crs}}{coordinate reference system of BBOX, e.g. 'OGC:CRS84' (EPSG:4326, WGS84 Longitude/Latitude)}
#' }
#'
#' The WCS query is parameterized using a rectangular extent derived from the above AOI specification, after conversion to the native CRS (EPSG:5070) of the ISSR-800 grids.
#'
#' Variables available from this WCS can be queried using \code{WCS_details(wcs = 'ISSR800')}.
#'
#' @note There are still some issues to be resolved related to the encoding of NA Variables with a natural zero (e.g. SAR) have 0 set to NA.
#'
#' @return A SpatRaster (or RasterLayer) object containing indexed map unit keys and associated raster attribute table or a try-error if request fails. By default, spatial classes from the `terra` package are returned. If the input object class is from the `raster` or `sp` packages a RasterLayer is returned.
#' @examples
#' \dontrun{
#' library(terra)
#'
#' # see WCS_details() for variable options
#' WCS_details(wcs = 'ISSR800')
#'
#' # get wind erodibility group
#' res <- ISSR800.wcs(list(aoi = c(-116, 35, -115.5, 35.5), crs = "EPSG:4326"),
#' var = 'weg', res = 800)
#' plot(res)
#' }
#' @export
ISSR800.wcs <- function(aoi, var, res = 800, quiet = FALSE) {
## vintage of source data
# TODO: use remote metadata
# --> must add to load-balancer
# .vintage <- readLines('http://casoilresource.lawr.ucdavis.edu/wcs-files/...')
# hard-coded
.vintage <- 'FY2024'
if (!requireNamespace("terra")) {
stop("package 'terra' is required", call. = FALSE)
}
# sanity check: AOI specification
if (!inherits(aoi, c('list', 'Spatial', 'sf', 'sfc', 'bbox', 'RasterLayer', 'SpatRaster', 'SpatVector'))) {
stop('invalid `aoi` specification', call. = FALSE)
}
# reasonable resolution
if (res < 400 || res > 1600) {
stop('`res` should be within 400 <= res <= 1600 meters')
}
# match variable name in catalog
var.cat <- sapply(.ISSR800.spec, '[[', 'dsn')
var <- match.arg(tolower(var), choices = var.cat)
# get variable specs
var.spec <- .ISSR800.spec[[var]]
# 2024-04-23: updated grid system
# 3620, 5769, 1 (nrow, ncol, nlyr)
# -2356800, 2258400, 276800, 3172800 (xmin, xmax, ymin, ymax)
# authoritative CONUS = grid
.crs <- 'EPSG:5070'
.grid <- terra::rast(nrows = 3620, ncols = 5769, crs = .crs,
extent = terra::ext(-2356800, 2258400, 276800, 3172800))
# compute BBOX / IMG geometry in native CRS
wcs.geom <- .prepare_AEA_AOI(aoi, res = res, native_crs = .crs)
## TODO: investigate why this is so
# sanity check: a 1x1 pixel request to WCS results in a corrupt GeoTiff
if (wcs.geom$width == 1 && wcs.geom$height == 1) {
stop('WCS requests for a 1x1 pixel image are not supported, try a smaller resolution', call. = FALSE)
}
# sanity check: keep output images within a reasonable limit
# limits set in the MAPFILE
max.img.dim <- 5000
# check image size > max.img.dim
if (wcs.geom$height > max.img.dim || wcs.geom$width > max.img.dim) {
msg <- sprintf(
'AOI is too large: %sx%s pixels requested (%sx%s pixels max)',
wcs.geom$width,
wcs.geom$height,
max.img.dim,
max.img.dim
)
stop(msg, call. = FALSE)
}
# base URL + parameters
base.url <- 'http://casoilresource.lawr.ucdavis.edu/cgi-bin/mapserv?'
service.url <- 'map=/soilmap2/website/wcs/issr800.map&SERVICE=WCS&VERSION=2.0.1&REQUEST=GetCoverage'
# unpack BBOX for WCS 2.0
xmin <- wcs.geom$bbox[1]
ymin <- wcs.geom$bbox[2]
# xmax and ymax are now calculated from AOI dimensions and resolution
# xmax <- wcs.geom$bbox[3]
# ymax <- wcs.geom$bbox[4]
# recalculate x/ymax based on xmin + resolution multiplied by AOI dims
xmax2 <- xmin + res * wcs.geom$width
ymax2 <- ymin + res * wcs.geom$height
## TODO: source data are LZW compressed, does it make sense to alter the compression (e.g. Deflate) for delivery?
# compile WCS 2.0 style URL
u <- paste0(
base.url,
service.url,
'&COVERAGEID=', var.spec$dsn,
'&FORMAT=image/tiff',
'&GEOTIFF:COMPRESSION=LZW',
'&SUBSETTINGCRS=EPSG:5070',
'&FORMAT=', var.spec$type,
'&SUBSET=x(', xmin, ',', xmax2, ')',
'&SUBSET=y(', ymin, ',', ymax2, ')',
'&RESOLUTION=x(', res, ')',
'&RESOLUTION=y(', res, ')'
)
# get data
tf <- tempfile()
dl.try <- try(
suppressWarnings(
curl::curl_download(u, destfile = tf, mode = 'wb', handle = .soilDB_curl_handle(), quiet = quiet)
),
silent = TRUE
)
if (inherits(dl.try, 'try-error')) {
message('bad WCS request')
return(dl.try)
}
# load pointer to file and return
r <- try(terra::rast(tf), silent = TRUE)
if (inherits(r, 'try-error')) {
message(attr(r, 'condition'))
stop('result is not a valid GeoTIFF', call. = FALSE)
}
## NOTE: terra (as of 1.6-28) will create 0-indexed grids sometimes when
## values(x) <- function_that_returns_factors(...)
##
## soil texture grids remain indexed from 1 for this reason
##
## TODO: this isn't quite right... '0' is returned by the WCS sometimes
# specification of NODATA using local definitions
# NAvalue(r) <- var.spec$na
terra::NAflag(r) <- 0
# load all values into memory
terra::values(r) <- terra::values(r)
# remove tempfile
unlink(tf)
# set layer name in object
names(r) <- var.spec$desc
# test for all NA
# if TRUE, we cannot process RATs
.allNA <- terra::global(r, fun = "isNA")$isNA == terra::ncell(r)
# message when all cells are NA
if(.allNA) {
message('all cells are NA')
}
# optional processing of RAT
if (!is.null(var.spec$rat) && !.allNA) {
# get rat
rat <- try(suppressWarnings(read.csv(var.spec$rat, stringsAsFactors = FALSE)), silent = TRUE)
# trap missing RAT
if (inherits(rat, 'try-error')) {
message("\nFailed to download RAT from ", var.spec$rat, "; returning integer grid")
return(r)
} else {
# the cell value / ID column is always the 2nd column
# name it for reference later
names(rat)[2] <- 'ID'
# re-order columns by name
# there may be > 2 columns (hex colors, etc.)
col.names <- c('ID', names(rat)[-2])
# make categories + RAT
r <- terra::as.factor(r)
r.rat <- terra::cats(r)[[1]]
# merge basic RAT + ISSR800 RAT
rat <- merge(r.rat[, 'ID', drop = FALSE], rat, by = 'ID', all.x = TRUE, sort = FALSE)
# register RAT
levels(r) <- rat
# set color table if there is a column named 'hex'
if('hex' %in% names(rat)) {
terra::coltab(r) <- rat[, c('ID', 'hex')]
}
}
}
# align to authoritative grid
terra::ext(r) <- terra::align(terra::ext(r), .grid)
input_class <- attr(wcs.geom, '.input_class')
if ((!is.null(input_class) && input_class == "raster") ||
getOption('soilDB.return_Spatial', default = FALSE)) {
if (requireNamespace("raster")) {
r <- raster::raster(r)
}
}
# set metadata
terra::metags(r) <- c(description = var.spec$desc, vintage = .vintage)
return(r)
}
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