# Meteonorm Observation

**Meteonorm Observation** provides near real-time measurements of solar irradiance.
Unlike ground-based measurement systems, this product relies on satellite-based irradiance observations, providing
consistent coverage, independent of local weather station availability.

## Coverage

Meteonorm Observation is available on the whole globe. Quality is best for
**longitudes from 130°W to 180°E** and **latitudes from 60°S to 60°N**, covered by
four geostationary weather satellites:

- GOES-East
- MSG (Meteosat Second Generation)
- IODC (Indian Ocean Data Coverage)
- Himawari

![data-observation-fig1](./data-observation-fig1.png)
**Figure 1:** _Global data coverage in Meteonorm Observation, showing the used bounding boxes
of the geostationary satellites including the high-resolution imagers (GOES-E-C and MSG-HRV).
ERA5 and GFS provide data in areas not covered by the satellites._


For locations that lack satellite coverage, as well as for the non-radiation parameters `temperature`
and `snow_depth`, we use the best available sources, depending on the location.


## Temporal Resolution

Weather satellite data is available at temporal intervals of **10 to 15 minutes**.


## Spatial Resolution

Satellite data is projected onto a regular latitude/longitude grid with a
**standard resolution of 0.0625°** (~5–7 km).

For enhanced coverage over **North America and Europe**, we leverage high-resolution
imagers (GOES-E-C and MSG-HRV) to provide a superior **0.025° resolution** product,
which equates to approximately 2–3 km.

## Accuracy

The accuracy of Meteonorm's satellite-based global radiation data is quantified using the
relative root mean square error (rel. RMSE). The typical accuracy varies with the time
resolution of the data.

| Time resolution | Typical Accuracy (rel. RMSE) |
| :-------------- | :--------------------------- |
| Hourly values   | 20%                          |
| Daily values    | 10%                          |
| Monthly values  | 5%                           |


Satellite-based measurements are comparable in accuracy to
high-quality ground-based pyranometers (radiation sensors), which typically are in the
5-10% range. A key advantage of satellite-based measurements is their immunity to common
issues that affect ground-based measurement systems, such as soiling or disruptions.