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{
  "@context": {
    "@vocab": "https://schema.org/", 
    "xsd": "https://www.w3.org/TR/xmlschema-2/#",
    "rdfs": "http://www.w3.org/2000/01/rdf-schema#",
    "dc": "http://purl.org/dc/terms/",
    "dcat": "https://www.w3.org/ns/dcat#",
    "freq": "http://purl.org/cld/freq/",
    "qudt": "http://qudt.org/schema/qudt/",
    "qudt-units": "http://qudt.org/vocab/unit/",

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---
title: "Using the geoconnex Reference Feature Server with R"
format:
  html:
    code-fold: show
    toc: true
    toc-location: left
    toc-depth: 4
    toc-expand: 3
    page-layout: full

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PREFIX schema: <https://schema.org/>
PREFIX gsp: <http://www.opengis.net/ont/geosparql#>
PREFIX wiki: <https://www.wikidata.org/wiki/>
PREFIX hyf: <https://www.opengis.net/def/schema/hy_features/hyf/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

SELECT ?dataset ?variableName ?temporalCoverage WHERE {
  # Bind the @id of the mainstem of interest
  BIND(<https://geoconnex.us/ref/mainstems/1009561> AS ?mainstem)
  

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{
  "type": "CoverageCollection",
  "domainType": "PointSeries",
   "parameters": {
        "discharge": {
          "type": "Parameter",
          "description": {"en":"Water discharge in cubic feet per second"},
          "observedProperty": {
            "label": {"en":"Discharge"},
            "id": "http://waterdata.usgs.gov/nwisweb/rdf?parmCd=00060"

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<gml:FeatureCollection
    xmlns:gml="http://www.opengis.net/gml/3.2"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:wml2="http://www.opengis.net/waterml/2.0"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:om="http://www.opengis.net/om/2.0"
    xmlns:sa="http://www.opengis.net/sampling/2.0"
    xmlns:sams="http://www.opengis.net/samplingSpatial/2.0"
    xmlns:swe="http://www.opengis.net/swe/2.0" gml:id="USGS.waterservices" xsi:schemaLocation="http://www.opengis.net/waterml/2.0 http://schemas.opengis.net/waterml/2.0/waterml2.xsd">
    <gml:featureMember>

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library(sf)
library(mapview)

# read identifiers for Colorado River and Colorado River (TX) into simple features 
colorado_river <- sf::read_sf("https://geoconnex.us/ref/mainstems/29559")
colorado_river_tx <- sf::read_sf("https://geoconnex.us/ref/mainstems/2639515")


## Function that constructs query to retrive the latest discharge observation from the USGS

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https://labs.waterdata.usgs.gov/sta/v1.1/Locations?$filter=properties/mainstemURL%20eq%20%27https://geoconnex.us/ref/mainstems/29559%27&$expand=Things($select=id)/Datastreams($filter=properties/ParameterCode%20eq%20%2700065%27)/Observations($top=1)&$resultFormat=GeoJSON"

https://labs.waterdata.usgs.gov/sta/v1.1/Locations?$filter=properties/mainstemURL%20eq%20%27https://geoconnex.us/ref/mainstems/29559%27&$expand=Things($select=id)/Datastreams($filter=properties/ParameterCode%20eq%20%2700065%27)/Observations($top=1)&$resultFormat=GeoJSON"

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##packages used
require(sf)
require(SPARQL)
# remotes::install_github("cran/SPARQL") this is archived by cran grrrr
require(mapview)
require(dplyr)
library(stringi)

# start gage
gage_uri <- "https://geoconnex.us/ref/gages/1118104"