PROBA-V Collection 2 Level-3 data are global composites on daily (S1) and five-daily (S5, only for 100 m products) basis. The aim is to optimally combine multiple observations into a single and cloud-free global synthesis image. Atmospherically uncorrected (Level-2A) data are the basis for the TOA synthesis products. The PROBA-V L3 products are available in 3 resolutions 1km, 300m and 100m.
Level-3 algorithm and data compositing
The processing descriptions of Level-1 and Level-2A are also applicable. The compositing into synthesis images is performed by the Level 3 Processor. The aim is to optimally combine multiple observations into a single and cloud-free global synthesis image. Atmospherically uncorrected (Level 2A) are the basis for the TOA synthesis products. Cloud coverage is minimized through discarding pixels that were labelled as cloudy by the cloud detection algorithm. In addition, angular variations are minimized, while global coverage is maximized. The S10 compositing is applied to avoid spatial coverage gaps resulting from clouds and the non-global daily swath coverage for the 100 m data. L2A data are combined into a global Level-3 synthesis through application of a Maximum Value Composite (MVC) technique (see among others Holben, 1986 and Tarpley et al., 1984). This technique selects the maximum TOA NDVI (which is additionally calculated within the compositing algorithm) pixel values. The following TOA synthesis products are generated:
- S1 (1-day syntheses)
- For the 100 m product, also S5 TOA data files are available. PROBA-V 100 m S5 products are comparable with full-coverage 300 m S1 products and are not real syntheses. Due to the narrow swath of the 100 m camera, there is only overlap in observations for latitudes > ~40° . This means that only poleward of this latitude compositing rules can be applied and that within ~40° S – 40° N the reflectances observed at one of the five days are given.
The layers include:
TOA reflectance for bands Blue, Red, NIR and SWIR
Angular information: solar and viewing zenith and azimuth angles
Status map information
The TIME grid dataset in the S5 files provides per pixel information at which day the observations were taken. This information is provided in minutes since the start of the synthesis period (day 1, 00:00 UTC). Check the Products User Manual for more detailed information.
Level-3 Quality assurance
In the Level 3 TOA S1 and S5 product files, the quality indicator is located in the SM (Status Map) Dataset within the QUALITY Group. The SM Dataset contains a quality state indicator per pixel, consisting of an observation indicator (clear, cloud, ice, shadow, undefined), a land/sea flag, and a radiometric quality indicator. Check the Products User Manual for a list of the various quality bit values and how to read them. The Status Map information can be easily read in most programming languages.
A Quality Webpage is available and provides information on the Quality Assessment and the various methods applied to maintain PROBA-V’s data quality at the highest possible level, from the raw satellite observations through the value-added products available at the PROBA-V Data Portal.
Digital Object Identifier (DOI)
European Space Agency, 2023, PROBA-V Level-3 TOA reflectance Data (S1, S5) Collection 2,
Spatial coverage: 75°N, 56°S, 180°W, 180°E
2013-10-16 – 2020-06-30 (for 1 km and 300 m)
2014-03-12 – 2020-06-30 (for 100 m)
Mission status: Complete
Orbit type: Sun-synchronous
European Space Agency, 2023, PROBA-V Level-3 TOA reflectance Data (S1, S5), Collection 2