Resample Type:
- None - no resampling.
- Average - mean value within resample period (fixed-window averaging without overlap). This is also known as a 'box-car' or ensemble average.
- Minimum/Maximum - most extreme minimum and maximum values within resample period.
Resample Period:
- Minute
- Hour
- Day
When resampling is selected:
- The timestamps in the data series correspond to the centre of each resampling interval. (Data downloaded prior to 15 Feb 2013: timestamps were at beginning of interval). The resample interval always begins and ends at an integer multiple of the resample period, so minutes on the minute, hours on the hour, days on the day, etc.
- If the date/time range on the search has limits that are within a resampling interval, the date/time endpoints are extended to include the entire resampling interval. For example, when daily resampling is selected from 03:00:00.000 on Monday to 20:00:00.000 on Thursday, the date range is extended to 00:00:00.000 on Monday to 23:59.59.999 on Thursday.
- Note that tides are not filtered out in resampled products.
- No anti-alias filtering is done. This is why only averaging and min/max are offered at this time. Box-car / ensemble averaging is an easily understood and ubiquitous process that is actually a partially effective low-pass anti-alias filter. For more information, see this page on data reduction and time-averaging.
- Average and Minimum/Maximum values will not be provided if less than a certain percentage (default 80%) of the expected samples per resampling interval are present (either because of data gaps or low data quality). (Data downloaded before 15 Feb 2013: No data completeness or quality assurance was tested for.)
More options may be available in the future. For more complex subsampling, CodeRunner (see CodeRunner Help ) is an alternative resource.