Time Series

Returns GNSS measurements for one or more stations over a time range. Use it to get Zenith Total Delay (ZTD), Precipitable Water Vapour (PWV), and per-satellite data for historical analysis.

Get station ids from Stations first.

Request format

POST https://api.skyfora.com/api/v1/measurements/query

curl -X POST https://api.skyfora.com/api/v1/measurements/query \
  -H "X-API-Key: your-api-key-here" \
  -H "Content-Type: application/json" \
  -d '{
    "start_time": "2026-03-20T00:00:00Z",
    "end_time": "2026-03-21T00:00:00Z",
    "station_ids": ["4f9b1c2e-6a70-4a3e-9a4f-2d8f5b7c0e11"],
    "data_vars": ["ztd", "ztd_sigma"]
  }'

import requests

resp = requests.post(
    "https://api.skyfora.com/api/v1/measurements/query",
    headers={"X-API-Key": "your-api-key-here"},
    json={
        "start_time": "2026-03-20T00:00:00Z",
        "end_time": "2026-03-21T00:00:00Z",
        "station_ids": ["4f9b1c2e-6a70-4a3e-9a4f-2d8f5b7c0e11"],
        "data_vars": ["ztd", "ztd_sigma"],
    },
)
resp.raise_for_status()
rows = resp.json()["data"]

Required parameters

Optional parameters

Response format

The response is JSON: one row per station and epoch, in time order.

{
  "data": [
    {
      "timestamp": "2026-03-20T12:00:00.000Z",
      "station_id": "4f9b1c2e-6a70-4a3e-9a4f-2d8f5b7c0e11",
      "display_name": "RAW_RAAS",
      "ztd": 2353.5,
      "ztd_sigma": 4.0
    }
  ],
  "count": 1
}

Per-satellite variables come as comma-separated strings in the order of prn; see Variables for each format. A row with satellite variables:

{
  "timestamp": "2026-03-20T12:00:00.000Z",
  "station_id": "4f9b1c2e-6a70-4a3e-9a4f-2d8f5b7c0e11",
  "display_name": "RAW_RAAS",
  "prn": "E03,E05,G08",
  "el": "22.3,74.2,9.8",
  "az": "278.2,255.4,94.4"
}

Intervals

With interval_seconds, the response has one row per station and interval instead of one per observation. timestamp is the start of the interval.

The quality filter applies before the mean. An interval with no observation for a station has no row for it.

Intervals make long ranges smaller to download and easier to plot. Use 900 (15 minutes) or 3600 (1 hour) for weeks or months of data.

Data checks and quality control

By default, the response contains only observations that pass the Skyfora quality filter. Set raw: true to get all observations, including the excluded ones.

Skyfora calculates each observation with precise point positioning (PPP): a station position and tropospheric delay solved from satellite signals and precise satellite orbit and clock corrections. An observation is returned only when that solution is stable and the station tracked enough good signals:

A gap in the response means the station sent no observations in that period, or none passed these checks. To tell the two apart, repeat the request with raw: true.

The observation interval is different for each station. Read resolution_seconds from GET /stations to get the epoch interval of a station.

Limits

All observations in the time range come back in one response. There is no pagination.

Data points

The size of a request is counted in data points: the epochs in the range, summed over the stations. A station's epoch is its observation rate, resolution_seconds in Stations, which differs between networks. When interval_seconds is longer than that, each interval counts once.

For stations with a 30-second resolution:

Each organization has a data-point limit per request. A request over the limit is rejected with 413 Content Too Large before it runs, and the error message states the limit. Set interval_seconds, or split a larger request by time range or by groups of stations and combine the results.