Iterate over Spatial* object features and submit spatial queries to the SDA web-service.
SDA_query_features(x, id='pedon_id')
a Spatial*
object with more than 1 feature, any defined coordinate system
the column name in x
that contains a unique ID for each feature
A dataframe containing the results.
The SDA website can be found at http://sdmdataaccess.nrcs.usda.gov. A detailed vignette can be found at https://r-forge.r-project.org/scm/viewvc.php/*checkout*/docs/soilDB/SDA-tutorial.html?root=aqp.