awdb (version 0.1.2)

get_elements: Get Station Elements

Description

Get station elements from the USDA National Water and Climate Center Air and Water Database REST API. Elements are soil, snow, stream, and weather variables measured at AWDB stations.

Usage

get_elements(aoi = NULL, elements, awdb_options = set_options(), as_sf = FALSE)

Value

if as_sf, an sf table, otherwise a simple data.frame. The number of rows depends on the number of stations and element parameters. Time series data are included as a list column named "element_values".

Arguments

aoi

sfc POLYGON scalar, the area of interest used for performing a spatial filter on available stations in network. If NULL (the default), no spatial filter is performed.

elements

character vector, abbreviations or codes for variables of interest (e.g., "SMS" for "Soil Moisture Percent"). See Details for available elements and codes.

awdb_options

an awdb_options list with additional query parameters.

as_sf

boolean scalar, whether to return the data as an sf table. Default is FALSE. Repeating the spatial data across each station element and its time series can be costly.

Details

This endpoint will accept the following query parameters via set_options():

• duration

• begin_date

• end_date

• period_reference

• central_tendency

• return_flags

• return_original_values

• return_suspect_values

The following can also be passed to filter stations:

• station_names

• dco_codes

• county_names

• hucs

• active_only

You may also specify networks and request_size. The networks parameter is used internally to build unique station triplet identifiers of the form station:state:network which are then passed to the endpoint, so it serves to filter stations to just those networks. The request_size parameter is for handling rate limits, which are based on the number of elements - a hard value to measure directly, so this parameter is more a rule of thumb than a strict standard. If processing is slow for you, you may find experimenting with this parameter useful.

See set_options() for more details.

Element Format

Elements are specified as triplets of the form elementCode:heightDepth:ordinal. Any part of the element triplet can contain the * wildcard character. Both heightDepth and ordinal are optional. The unit of heightDepth is inches. If ordinal is not specified, it is assumed to be 1. Here are some examples:

• "WTEQ" - return all snow water equivalent values.

• "SMS:-8" - return soil moisture values observed 8 inches below the surface.

• "SMS:*" - return soil moisture values for all measured depths.

Examples

# get snow water equivalent values around Bear Lake
get_elements(bear_lake, elements = "WTEQ")

# return as sf table
get_elements(bear_lake, elements = "WTEQ", as_sf = TRUE)