Data
Preliminary and Definitive Data Types
Magnetometer data from the USGS observatories are available in two forms, ‘preliminary’ and ‘definitive’. Preliminary data are available in Raw Real-Time Stack Plot, but they are unprocessed, they have not been explicitly adjusted for long-term baseline drift, and they have not been cleaned of occasional spikes and step offsets. Having said that, preliminary data are reasonably good representations of field variation occurring over time scales shorter than a few days. On the other hand, definitive data are fully processed, they have been adjusted for baseline drift, and they can, therefore, be considered to be 'absolute'; definitive data have also been cleaned for spikes, step offsets, and other artifacts and contamination. Insofar as they better represent the actual time-dependent behavior of the Earth’s magnetic field, definitive data are superior to preliminary data. Definitive data can be used for either short-term or long-term studies of the geomagnetic field. But since producing definitive data requires the careful inspection of the data and the application of specialized software, they are not made available until some time after their initial collection.
Flux-gate Data (H,D,Z) Specifications
| Magnetic resolution | 0.1 nT |
| Temporal resolution | 1-minute, 0.1667 Hz |
| Filter type | Gaussian, using 91 1-second samples |
| Time stamp | Universal time, filter-centered |
| Preliminary-data availability | Near-real time, 12-24 minute delay |
| Definitive-data accuracy | 5 nT |
Proton Data (F) Specifications
| Magnetic resolution | 0.1 nT |
| Temporal resolution | 1-minute, 0.1667 Hz |
| Filter type | Boxcar, using 3 20-second samples |
| Time stamp | Universal time, filter-centered |
| Preliminary-data availability | Near-real time, 12-24 minute delay |
| Definitive-data accuracy | 1 nT |
Contacts
For requests for Intermagnet CDs, and older USGS CDs, all of which are free of charge:
For general enquiries about USGS Geomagnetism Program data, including specialized requests for USGS data:
