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Get SSURGO ZIP files from Web Soil Survey 'Download Soils Data'

Source: R/createSSURGO.R
downloadSSURGO.Rd

Download ZIP files containing spatial (ESRI shapefile) and tabular (TXT) files with standard SSURGO format; optionally including the corresponding SSURGO Template Database with include_template=TRUE.

Usage

downloadSSURGO(
  WHERE = NULL,
  areasymbols = NULL,
  destdir = tempdir(),
  exdir = destdir,
  include_template = FALSE,
  db = c("SSURGO", "STATSGO"),
  extract = TRUE,
  remove_zip = FALSE,
  overwrite = FALSE,
  quiet = FALSE
)

Arguments

WHERE

A SQL WHERE clause expression used to filter records in sacatalog table. Alternately WHERE can be any spatial object supported by SDA_spatialQuery() for defining the target extent.

areasymbols

Character vector of soil survey area symbols e.g. c("CA067", "CA077"). Used in lieu of WHERE argument.

destdir

Directory to download ZIP files into. Default tempdir().

exdir

Directory to extract ZIP archives into. May be a directory that does not yet exist. Each ZIP file will extract to a folder labeled with areasymbol in this directory. Default: destdir

include_template

Include the (possibly state-specific) MS Access template database? Default: FALSE

db

Either "SSURGO" (default; detailed soil map) or "STATSGO" (general soil map).

extract

Logical. Extract ZIP files to exdir? Default: TRUE

remove_zip

Logical. Remove ZIP files after extracting? Default: FALSE

overwrite

Logical. Overwrite by re-extracting if directory already exists? Default: FALSE

quiet

Logical. Passed to curl::curl_download().

Value

Character. Paths to downloaded ZIP files (invisibly). May not exist if remove_zip = TRUE.

Details

To specify the Soil Survey Areas you would like to obtain data you use a WHERE clause for query of sacatalog table such as areasymbol = 'CA067', "areasymbol IN ('CA628', 'CA067')" or areasymbol LIKE 'CT%'.

When db="STATSGO" the WHERE argument is not supported. Allowed areasymbols include "US" and two-letter state codes e.g. "WY" for the Wyoming general soils map.

Pipe-delimited TXT files are found in /tabular/ folder extracted from a SSURGO ZIP. The files are named for tables in the SSURGO schema. There is no header / the files do not have column names. See the Soil Data Access Tables and Columns Report: https://sdmdataaccess.nrcs.usda.gov/documents/TablesAndColumnsReport.pdf for details on tables, column names and metadata including the default sequence of columns used in TXT files. The function returns a try-error if the WHERE/areasymbols arguments result in

Several ESRI shapefiles are found in the /spatial/ folder extracted from a SSURGO ZIP. These have prefix soilmu_ (mapunit), soilsa_ (survey area), soilsf_ (special features). There will also be a TXT file with prefix soilsf_ describing any special features. Shapefile names then have an a_ (polygon), l_ (line), p_ (point) followed by the soil survey area symbol.

See also

createSSURGO()