402 reviews
Content rating
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About this app

CrowdMag is a tool that measures the local magnetic field using your smartphone! The app displays the data as a graph or a map in units of nanotesla (nT; one nanotesla equals 10^−9 Tesla). The local magnetic field components measured by CrowdMag are the Z (downward component), H (horizontal intensity), and F (total intensity). Use CrowdMag for measuring magnetic data during your outdoor adventures or to conduct your own homegrown science! To perform your own experiments or analyze your observations, export your data as a CSV file. Optionally, your magnetic data may be shared with NOAA to help scientists understand more about Earth’s magnetic field!

What is new!

CrowdMag is going active! When you go out for a walk, run, or other outdoor activities, use CrowdMag to measure the magnetic data along your path and save the data as a “magtivity”. Save, list, export or delete magtivities to create a complete magnetic field map of your area. We particularly encourage you to share your magtivities with our research group at NOAA and to have multiple magtivities along the same path so that we can stack the data to reduce the noise.

Getting a new phone? Don’t worry! You can now export a backup of your CrowdMag and save it on your computer. If you have to reset your phone, or switch to a new phone, you can now import your backup and continue using CrowdMag without losing your status for data contributed, areas covered, or magtivities completed.

CrowdMag’s magnetic calculator provides magnetic variation (declination), the magnetic field’s dip angle, total magnetic field and other magnetic field components (as well as their associated uncertainties) based on the latest World Magnetic Model (WMM2020).

CrowdMag Features:

- Create your own magnetic activity (magtivity)
- Customize recording frequency and location accuracy
- Interactive Google Map provides a map of your magnetic data
- Graph your data as a time series line chart
- Check the quality of the data by comparing it with the WMM
- Export your data as a CSV file
- Clear stored data on your phone
- Optionally share your data with NOAA
- See generalized crowdsourced magnetic data from other users
- Live magnetic compass
- Current solar magnetic disturbance
- Expected magnetic field calculator
- Uses the most recent magnetic field model (WMM2020)
- Export data via email, Google Drive and other options
- Export CrowdMag backup to save your contributions' status and data
- Import CrowdMag backup (works across different phone platforms)

Visit https://ngdc.noaa.gov/geomag/crowdmag.shtml to see crowdsourced magnetic data.

A quick tutorial on CrowdMag app usage https://www.noaa.gov/education/resource-collections/data/tiny-tutorials/crowdmag
Updated on
Dec 3, 2022

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.
No data shared with third parties
Learn more about how developers declare sharing
No data collected
Learn more about how developers declare collection
402 reviews
Kelly Hanson (Mogas928)
November 6, 2022
It's the only app that's going to let you know when the magnetic reversal is getting closer to happening because the f****** media isn't going to do it so y'all better keep a close eye see where that North and South magnetic poles are doing
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Amanda Sousa
February 4, 2021
We love the app! I fell sensitive about the electromagnetic waves and radiation and we are specially today experiencing a high level variation from our pattern. We live in the middle of south America and we saw an incredible increase of our numbers. From 23.000nt to 149.000 and it's not going back normal! From 02 Jan 2021. Even our phones started to break with no apparent Reason....
20 people found this review helpful
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Rand Flory
March 12, 2022
I use the app to determine magnetic declination at my location. It works well, but I have a suggestion as to the readout of the declination. BY CONVENTION, positive declination is east and negative declination is West. As I sit here, that is easy to remember. In the field, it may not be. To reduce confusion when setting the declination on a compass, which marked East and West, but NOT +/-, how about reporting the declination like this: 10.43 (E), or -10.43 (W) Adding this would be a big help.
10 people found this review helpful
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What's new

* New 3D compass
* Improved Magtivity recording
* Bug fixes
* New privacy policy in settings