SOLAR RADIATION Maps in real time
|Last update: April 2020|
Subscription to 15 min Global Horizontal Irradiation bitmap Maps in Wh/m² and in TIFF format delivered in real time (h-15 min) on a given area, during daylight time from 3:00 TU to 20:45 UT
The Customer communicates the rectangular box over the area cover by the service.
To limit the load on the service, the GHI values are divided by a factor of 1.2 to be stored in 8 bit TIFF format, leading to the approximate precision of 1 watt.
It is also possible to GHI maps with a 10^-2 precision in 16 bit TIFF images.
Archive: please note that the Hc3v5-15mapGHI maps are conserved for the last 4 weeks.
The Hc3v5-15mapGHI includes the post-processing layers that are available in the time series HC3v5. Here they are:
- Each pixel is re-interpolated in time at an exact 15 min UTC
- All pixels where sun elevation is below 2 degrees are interpolated
- Altitude correction (using SRTM Altitude database)
- Kc-max correction
- Bias correction
1. Each pixel is re-interpolated in time at an exact 15 min UTC
To be able to apply the re-interpolation, this step implies to already have the next slot. Let's take as example Germany maps today at 10:15.
HC15mapGHI creates a new map [server]/germany/germany_irr_1504221000.tif. It contains GHI irradiation extracted from the sole 1504221000 MSG slot, i.e. irradiation at approximately 10:11 UT for Germany.
Hc3v5-15mapGHI generates 2 maps:
- [server]/germany-hc3v5/germany_irr_1504221000.tif contains GHI irradiation from 09:45 to 10:00 UT. This map is final.
- [server]/germany-hc3v5/germany_irr_1504221015.tif contains GHI irradiation from 10:00 to 10:15 UT. This map is a 4 minutes forecast (for Germany) and will be updated 15 minutes later.
2. All pixels where sun elevation is below 2 degrees are interpolated
When the sun elevation is below 2 degrees, the previous service without post-processing layers (HC15mapGHI) was generating no data (pixel = 254). In the new service HC3v5-15mapGHI, the irradiation values are interpolated using an interpolation based on the persistance of the clearness index Kc (GHI/GHI_clearsky.
NB: this remark can be generalized for every missing MSG slot. The previous service without post-processing layers was generating no map for Germany, whereas the new service provides an interpolated maps based on Kc persistance.
3. 4. 5. Altitude, Kc_max and bias corrections
Altitude correction and Kc-max correction are bug fixes for altitude and albedo errors.
Bias correction is a global calibration of hc3v5 w.r.t. BSRN stations.