Near Real-Time Format Specification
The near real-time (NRT) file format is used as an exchange and submission format for certain parts of the O2A data flow framework.
NRT files are supposed to contain time series data. Time series data must
- be in sequential order,
- use ISO8601-compliant date/time formats,
- be free of duplicate rows,
- be free of duplicate timestamps,
- be free of trailing, leading, or in between blank/empty rows
Every column has a respective header, as well as every header has as many columns in the data rows.
Conventions
| Property | Requirement | Description |
|---|---|---|
| character encoding | mandatory | UTF-8 |
| column separator | mandatory | tabulators \t |
| end of line marker | mandatory | newline \n |
| column names | mandatory | first column must be datetime followed by columns representing valid parameter codes as defined in O2A REGISTRY |
| data values | mandatory | decimal and integer values, character values only when unit is declared as text |
| no values | mandatory | empty fields (null string or empty field respectively) |
| decimal symbol | mandatory | period . |
| datetime format | mandatory | yyyy-mm-dd HH:MM:SS.fff (ISO 8601[1]), datetime must be submitted in UTC |
| units | optional | may be given in square brackets [ ], following each parameter code, separated by a space |
| quality flags | optional | quality flags can be added to each column of data by an identical parameter code column followed by (quality_flag) or (qf) |
Quality Flags
Optional quality flags must use the Argo quality control flag scale for real-time and delayed-mode data[2].
| Value | Meaning | Description |
|---|---|---|
| 0 | no quality control performed | No quality control has been performed on the value. |
| 1 | good data | The value is good within the limits of the applied tests, not adjusted or statistically sound. |
| 2 | probably good data | The value should be used with caution. |
| 3 | probably bad data, potentially adjustable | The value should not be used without scientific adjustment. |
| 4 | bad data | The value should not be used. |
| 5 | value changed | The value has been changed. |
| 6 | not used | Reserved, not used. |
| 7 | not used | Reserved, not used. |
| 8 | estimated value | The value was interpolated, extrapolated or otherwise estimated. |
| 9 | missing value | The value is missing; the data field is empty. |
Example
Example of the data format for the "self-cleaning monitoring box" mounted on research vessel Sonne with metadata in O2A REGISTRY https://registry.o2a-data.de/items/7534 and no quality flags applied.
| datetime | vessel:sonne:smb_sonne:smb_a_1702:salinity [PSU] | vessel:sonne:smb_sonne:smb_a_1702:salinity (quality_flag) |
|---|---|---|
| 2026-06-01T00:00:00 | 34.4986 | 0 |
| 2026-06-01T00:00:01 | 34.4988 | 0 |
| 2026-06-01T00:00:02 | 34.4985 | 0 |
| 2026-06-01T00:00:03 | 34.4985 | 0 |
| 2026-06-01T00:00:04 | 34.4983 | 0 |
| 2026-06-01T00:00:05 | 34.4985 | 0 |
| 2026-06-01T00:00:06 | 34.499 | 0 |
| 2026-06-01T00:00:07 | 34.4982 | 0 |
| 2026-06-01T00:00:08 | 0 | |
| 2026-06-01T00:00:09 | 34.4987 | 0 |
References
A concise specification of the standardized exchange format can be found here:
Koppe, R., Immoor, S., & Anselm, N. (2019). Format specification for Near Real-Time format. https://doi.org/10.5281/zenodo.15783112
International Organization for Standardization (Feb. 2017): ISO 8601 Date and time format. url: https://www.iso.org/iso-8601-date-and-time-format.html ↩︎
Argo Data Management Team (June 2025): Argo user's manual. Tech. rep. url: https://doi.org/10.13155/29825 ↩︎