The Level 3 parameters section consists of the selection of variables and aggregators, and the selection of temporal and spatial aggregation parameters.
- At least one variable or expression with one aggregator has to be selected.
- All output variables of the processor selected are offered.
- Instead of a variable a band maths expression can be entered. Click into the invisible field in the Expression column to edit. This can also be used for the aggregation without L2 processing. The variables of the inputs available for the expression must be known in this case.
- The standard aggregators available are AVG, MIN_MAX, PERCENTILE (MEDIAN).
- Additional aggregators may be made available in processor bundles. They may have several variables and additional aggregator parameters. As an example, ON_MAX_SET requires the on-max variable in the Aggregator Parameters column and the set of additional (output) variables as comma-separated list in the Expression column.
- More than one variable/expression aggregator pair can be added with the ADD button.
A good-pixel expression can be specified to filter pixels that shall not be considered for the aggregation.
The timing parameters are:
- Stepping period: This parameter together with the time interval selected for the product set determines the number of Level 3 outputs generated. A selection of one year and a stepping period of 30 days will result in 12 30-day products. Tip: If you want to get monthly averages enter -30, in both stepping period and compositing period.
- Compositing period: This parameter determines the input data for one output. It may be equal to the stepping period.
The spatial parameters are:
- Spatial resolution: The size of the bin cell and thus the output pixel size.
- Supersampling: Determines whether input pixels are split spatially to avoid gaps in the output. A value higher than 1 required If the output pixel size is in the same order as the input pixel size.