soilDB (version 2.6.9)

mapunit_geom_by_ll_bbox: Fetch Map Unit Geometry from SDA

Description

Fetch map unit geometry from the SDA website by WGS84 bounding box. There is a limit on the amount of data returned as serialized JSON (~32Mb) and a total record limit of 100,000.

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 https://sdmdataaccess.nrcs.usda.gov. See examples for bounding box formatting.

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)
    
    #inspect
    head(res)
  } else {
    message('could not download XML result from SDA')
  }
 }
# }