Measurements
Query Global Navigation Satellite System (GNSS) measurement observations collected from reference station networks. Filter by time range, stations, and measurement variables.
By default, responses include only quality-filtered observations. Set
raw: true in the request body to include observations excluded by the
default quality filter.
Available measurement variables (data_vars):
The variables are sourced or derived from GNSS observations. The observation
rate may differ for each station. Read resolution_seconds from
GET /stations for the epoch interval of a given station.
| Variable | Description | Unit |
|---|---|---|
ztd |
Zenith Total Delay | mm |
ztd_sigma |
Zenith Total Delay uncertainty (standard deviation of the estimate) | mm |
pwv |
Precipitable Water Vapour | mm |
snr |
Carrier-to-noise density ratio (C/N0) per signal band | dB-Hz |
el |
Satellite elevation per satellite | degrees |
az |
Satellite azimuth per satellite | degrees |
prn |
Satellite pseudo-random noise (PRN) identifiers, included automatically when el, az, or snr is requested |
- |
How Precipitable Water Vapour is derived: Skyfora estimates Precipitable Water Vapour (PWV) from Zenith Total Delay (ZTD). The estimate also uses surface pressure, air temperature at 2 m, and relative humidity. These meteorological inputs come from the nearest suitable observation, or from a numerical weather prediction (NWP) model when no observation is available. Skyfora adjusts them for the height of the GNSS site. The API response does not return these inputs. They are not necessarily measured at the GNSS station itself.
The default response format is NetCDF-4 (CF-1.8 conventions), suitable for
use with Python xarray, MATLAB, or any NetCDF reader. To receive JSON instead,
set the Accept header to application/json.
Access is restricted to stations within your organization's entitled networks.
Authenticate with an organization-scoped API key via the X-API-Key header.