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This app measures magnetic field and show the data as graph or map in units of nanotesla (nT; one nanotesla equals 10^−9 tesla). Displays Z (downward component), H (horizontal intensity) and F (total intensity) of the local magnetic field vector. Data processing reduces the noise to about 1% of the actual magnetic field. We rotate the magnetic data from the phone’s orientation to the real-world coordinates. Use it for measuring magnetic data at a location or over an area. Export your data as a CSV file. Optionally, enable background reporting to help NOAA scientists understand more about the Earth’s magnetic field!

Use CrowdMag app as an offline magnetic calculator. Quickly get magnetic variation (declination) at remote sites or ships. Calculator gives magnetic variation, dip angle, total field and other magnetic field components for date and location based on the latest World Magnetic Model (WMM2015). The model is developed primarily using data from ESA’s SWARM satellites and it accurately predicts the main magnetic field anywhere on the globe. It also provides the uncertainty and the time change of the modeled magnetic field.

CrowdMag Features:

- Interactive Google Map showing your magnetic data
- Graph your data as time series
- Check the quality of the data by comparing with WMM
- Export your data as a CSV file
- Enable/disable background reporting
- Clear stored data on your phone
- Optionally share your data with NOAA
- Customize location accuracy
- See crowdsourced magnetic data from other users

Magnetic Calculator:

- Uses the most recent model (WMM2015)
- Compute Declination, Dip and Total Field and other components for given date and location (2014-2019)
- Autolocate your latitude/longitude
- Uncertainty
- Compass rose on a map
- Export data via email, Google Drive and other options

Visit for more information. The project is open sourced! Send us an email for app source code. Developers, let us know if you want to contribute magnetic data from your app to NOAA.

Note that continued use of GPS running in the background can dramatically decrease battery life.