Resample Type:
- None - no resampling. This is the default option for time series scalar data.
- Average - the mean value within resample period (fixed-window averaging without overlap). This is also known as a 'box-car' or ensemble average. It is subject to the 70% data completeness QAQC check. Only available with the clean data product option.
- Min/Max - only available for some plotting data products - the most extreme minimum and maximum values within resample period. It is subject to the 70% data completeness QAQC check; QAQC flags are taken from the extreme data points. (At this time, the time stamps of the minimum/maximum values are not provided in all data products, which is why this option is not currently offered for time series scalar data, but it will offered again once the full time-stamps are provided.)
- Min/Max+Avg - only available for some plotting data products - the combination of the min/max and average as described above. The average is always calculated from clean data and will be NaN if there is less than 70% data available after cleaning. QAQC flags for min/max+avg with automatic resampling are the worst flag in the resample period, which includes the 70% check on data completeness. This is the default option for time series scalar plots, other plots, such as the BHT, AGO, profile or staircase plots will have different options and defaults.
Resample Period:
Visible when an actionable resample type is selected, immediately to the right of the resample type. Current periods offered:
- 1 Minute
- 10 Minute
- 15 Minute
- 1 Hour
- 1 Day
- Automatic (plots only)
When resampling is selected:
- The timestamps in the data series correspond to the centre of each resampling interval. (Data downloaded prior to 13 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.
- All averages are calculated by adding all individual samples and then divide by the total number of samples. (Data downloaded before 13 Feb 2013: hourly and daily averages were weighted over 15-minute periods, that is, the average of each 15-minute period was calculated individually, and the hourly and daily averages were calculated from the 15-minute averages.)
- All resampled data products are subject to an additional QAQC check on data completeness. If any resample period does not contain at least 70% of the expected data, the QAQC flag for this period will be a failure (4), unless overridden by a manual QAQC flag, see the QAQC page. For live data, it is quite likely that the last resample period will not be complete and will be flagged; this is especially obvious for plots. The data completeness percentage was 80% from March 21, 2013 to to June 6, 2013. Prior to March 21, 2012, no data completeness or quality assurance testing was available. Future improvements will allow users to modify the data completeness threshold.
- (plots only) Automatic resampling chooses the most appropriate resample period for min/max or min/max+avg resampling, such that the amount of data returned is adequate for plotting.
More options will be available in the future as we work to improve the data products. Feedback is welcomed and encouraged. For custom resampling, users can develop their own matlab code in CodeRunner in the ONC computing environment (users can access all production data and code). See CodeRunner Help for more details.
File-name mode field
The resample type and period are added to the file-name when resampling is selected. Examples: 'avg1hour', 'MinMax10minute'.