soilDB (version 2.5)

mapunit_geom_by_ll_bbox: Fetch Map Unit Geometry from SDA

Description

Fetch map unit geometry from the SDA website by WGS84 bounding box.

Usage

mapunit_geom_by_ll_bbox(bbox, source = 'sda')

Arguments

bbox

a bounding box in WGS coordinates

source

the source database, currently limited to soil data access (SDA)

Value

A SpatialPolygonsDataFrame of map unit polygons, in WGS84 (long,lat) coordinates.

Details

The SDA website can be found at http://sdmdataaccess.nrcs.usda.gov. See examples for bounding box formatting.

References

http://casoilresource.lawr.ucdavis.edu/

Examples

# NOT RUN {
# fetch map unit geometry from a bounding-box:
# 
#         +------------- (-120.41, 38.70)
#         |                     |
#         |                     |
# (-120.54, 38.61) --------------+

# }
# NOT RUN {
if(requireNamespace("curl") &
    curl::has_internet() &
    require(sp) & 
    require(rgdal)) {

  # basic usage
  b <- c(-120.54,38.61,-120.41,38.70)
  x <- try(mapunit_geom_by_ll_bbox(b)) # about 20 seconds
  
  if(!inherits(x,'try-error'))
    # note that the returned geometry is everything overlapping the bbox
    # and not an intersection... why?
    plot(x)
    rect(b[1], b[2], b[3], b[4], border='red', lwd=2)
    
    
    # get map unit data for matching map unit keys
    in.statement <- format_SQL_in_statement(unique(x$MUKEY))
    q <- paste("SELECT mukey, muname FROM mapunit WHERE mukey IN ", in.statement, sep="")
    res <- SDA_query(q)
  } else {
    message('could not download XML result from SDA')
  }
# }