Help previous API user

[robtuley]

A previous Rainchasers API user was polling the URL:

http://api.rainchasers.com/v1/river/75148ca0-ee5e-4344-8534-db9a59ed4cd0
(the classic section of the Dee)
Parsing out the data: response[data][state][source][value]

This is now broken for them after the closure of the API, and I would like to help if possible.

[robtuley]

This is this river:

rainchasers/rivers/dee-horseshoe-falls-llangollen.yaml

Lines 1 to 22 in 63b95c4

	uuid: 75148ca0-ee5e-4344-8534-db9a59ed4cd0
	river: Dee
	section: "Horseshoe Falls to Llangollen"
	km: 3
	grade:
	text: 3/4
	value: 3.5
	desc: "The classic section of the Dee. At low to medium levels a pool-drop run often used to introduce beginners to grade 3 paddling, at high to spate flows an excellent playrun. The hardest rapid (Town Falls) is right at the takeout under the main bridge in Llangollen: take care as the small weir just below this is reputed to contain metal spikes. Takeout ~100m after the bridge on river left. The rapids at Mile End Mill at the outskirts of Llangollen provide an early takeout (or simply a park and playspot) if you want to miss out Town Falls."
	directions: "Cross the river from the A5 at Berwyn along the B5103 and park for the putin in the carpark on river left. To reach Horseshoe Falls (a weir) walk 5 minutes upstream from the carpark, it is possible to walk out the back the highest parking area down a long grass slope to the river. Takeout in the carpark on river left just downstream of the main bridge in Llangollen. Alternatively, if you only have one car, Park in Llangollen, paddle up the canal to the put-in, then back down the river. Lovely."
	putin:
	lat: 52.9807333
	lng: -3.1989739
	takeout:
	lat: 52.9703498
	lng: -3.1683108
	measures:
	- scrape: 0.45
	low: 0.52
	medium: 0.65
	high: 0.95
	huge: 1.25
	data_url: "rloi://4163"

[robtuley]

The gauge is this one: https://rivers-and-seas.naturalresources.wales/Station/4163?parameterType=1

[robtuley]

Probably the best solution to this because the user is simply polling the API for the value of the gauge (rather than an enriched calibrated reading) is to use the NRW API that is now available. Steps to sort would be:

• Sign up to get a subscription key on the NRW API linked above
• Adjust code to poll directly for station 4163 (you'll need to include a magic 'parameter' 38)
• Adjust the json parsing returned to get the location of the latest value

In this API, the station is defined as:

{
  "coordinates": {
    "latitude": 52.979148,
    "longitude": -3.3879242
  },
  "location": 4163,
  "nameEN": "Corwen",
  "nameCY": "Corwen",
  "statusEN": "Online",
  "statusCY": "Ar-lein",
  "url": "rivers-and-seas.naturalresources.wales/station/4163",
  "ngr": "SJ0690843324",
  "titleEn": "Dee at Corwen",
  "titleCy": "Afon Ddyfrdwy yng Nghorwen",
  "parameters": [{
    "parameter": 38,
    "paramNameEN": "River Level",
    "paramNameCY": "Lefel yr afon",
    "parameterStatusEN": "Level Rising",
    "parameterStatusCY": "Lefel codi",
    "units": "m",
    "latestValue": 1.061,
    "latestTime": "2020-12-23T20:00:00Z"
  }]
}

Note the magic 'parameter', you'll need it to query the API. The query you want is this (using my own subscription key):

GET https://api.naturalresources.wales/rivers-and-seas/v1/api/StationData/historical?location=4163&parameter=38 HTTP/1.1
Host: api.naturalresources.wales
Ocp-Apim-Subscription-Key: ********************

Request-Context: appId=cid-v1:da3195ce-128b-443d-bbe8-f679d032a677
Date: Wed, 23 Dec 2020 21:05:06 GMT
X-Powered-By: ASP.NET
Content-Length: 1699048
Content-Type: application/json; charset=utf-8

{
  "coordinates": {
    "latitude": 52.979148,
    "longitude": -3.3879242
  },
  "location": 4163,
  "nameEN": "Corwen",
  "nameCY": "Corwen",
  "statusEN": "Online",
  "statusCY": "Ar-lein",
  "url": "rivers-and-seas.naturalresources.wales/station/4163",
  "ngr": "SJ0690843324",
  "parameter": 38,
  "paramNameEN": "River Level",
  "paramNameCY": "Lefel yr afon",
  "titleEN": "Dee at Corwen",
  "titleCY": "Afon Ddyfrdwy yng Nghorwen",
  "parameterStatusEN": "Level Rising",
  "parameterStatusCY": "Lefel codi",
  "units": "m",
  "parameterReadings": [{
    "value": 0.683,
    "time": "2019-12-01T00:00:00Z"
  }, {
    "value": 0.683,
    "time": "2019-12-01T00:15:00Z"
  }, {
    "value": 0.682,
    "time": "2019-12-01T00:30:00Z"
  }, {
    "value": 0.682,
    "time": "2019-12-01T00:45:00Z"
<snip>

I think you'd want to parse out the last one (the most recent). I can't see a way to get just the latest value -- the only way seems to be to get all the most recent values from a different API endpoint and then extract just what you want (which is what rainchasers does).