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 NOAA > NESDIS > NCEI (formerly NGDC) > Geomagnetism

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 especially 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 and produce a more accurate magnetic field map.

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, the total magnetic field and other magnetic field components (as well as their associated uncertainties) based on the latest World Magnetic Model (WMM2020).

What is CrowdMag?

In NOAA’s CrowdMag project, we explore whether the digital magnetometers built in modern mobile smartphones can be used as scientific instruments. With CrowdMag mobile apps, phones all around the world can send magnetometer data to our research group. At our server, we check the quality of the magnetic data and share data with the public as aggregate maps and charts. Our goals are:

  1. To build, grow, and foster a worldwide community of citizen scientists and enthusiasts collecting magnetic field data and sharing it to further our understanding of the Earth’s magnetic field.
  2. Develop magnetic models and maps using the data shared by CrowdMag users in combination with data collected by ships, aircrafts and satellites, with an aim to fill in the gaps of professional mapping of Earth’s magnetic field.
  3. Success of the CrowdMag project depends on the participation of citizen scientists like you. Become a citizen scientist and join our research on Earth's geomagnetic field. The video below shows how using the CrowdMag smartphone app during your everyday activity will help us improve navigation for everyone.


In today’s era of GPS and other geospatial technologies, are compasses still needed? Yes! For a stationary device, GPS does not provide a pointing direction. Additionally, satellite signals can be jammed or masked. For example, it is extremely difficult to obtain GPS signals underwater. Earth's magnetic field (the geomagnetic field) provides us with an all-weather, any location referencing system. Earth acts like a giant spherical magnet and in general, its magnetic field resembles that generated by a dipole magnet (i.e., a straight bar magnet with a north and south pole) located at the center of Earth. Since ancient times, people have observed and used the geomagnetic field for navigation. Today, magnetic navigation is implemented on most planes, ships, and even on your smartphone, for safe and reliable navigation. As the geomagnetic field changes with both time and location, it is important to monitor its changes. Scientists use observatories from satellites and ship/airborne surveys to keep track of the geomagnetic field’s changes. Due to gaps in data coverage scientists are always looking for alternative ways to obtain geomagnetic data. CrowdMag mobile applications can potentially improve magnetic field models and magnetic navigation by filling in data gaps with existing technologies that capitalize on citizen science.


Who are we?

We are the geomagnetism group of NOAA's National Centers for Environmental Information (NCEI) and we conduct original research on the magnetic field of Earth. Our primary goal is to create and update models of the geomagnetic field to keep pace with Earth's constantly changing magnetic field. Our magnetic models are integrated into millions of smartphones, car and aircraft navigation systems, and GPS so that users know which way is north. See our frequently asked questions on geomagnetism.

CrowdMag Privacy Policy

In addition to the NOAA privacy policy, the CrowdMag app implements the following measure: CrowdMag data are collected anonymously. We do not collect personally identifiable information, including your name, email address, or your device's unique identification number. If you enable the “send data” option in the CrowdMag app, the following information will be sent to NOAA:

  • Magnetic field data from the phone's magnetic sensor
  • Time of measurement
  • Location of measurement
  • Location accuracy
  • The model of your phone (and thereby, we will know which type of sensor was used to collect the magnetic field data)

For the foreseeable future, CrowdMag data are stored in an internal, non-public database at the NOAA's National Centers for Environmental Information, Boulder, CO, U.S.A . Our magnetic field research team will use this data to assess the utility of incorporating crowdsourced magnetic field data for modeling Earth’s magnetic field. Using CrowdMag data, our team will periodically produce scientific products such as maps, graphs and/or mathematical models. In order to further geomagnetic field research, these products may be presented at meetings, be included in publications, or be made available to the public via the Internet.

Crowdsourced magnetic data

This map shows data collected from phones around the world! Displayed is the crowdsourced magnetic data collected in the past 24 hours from the CrowdMag app. For displaying older data, click the “+” sign on the map. We have added some uncertainty to each of the shown data points to ensure the privacy of our contributors. This map is updated every hour. The F channel represents Total Magnetic Field Strength, H channel represents the Magnetic Field’s Horizontal Component, and Z channel represents the Magnetic Field’s Vertical Component. Use the menu in the map’s top-right corner to access a different date range of data. Please note that the user locations are snapped to the nearest grid points (following a roughly 1x1 kilometer grid).

Be a citizen scientist!

Use your phone as a magnetic sensor! Here is an opportunity for you to be a part of our research on the geomagnetic field. Install the CrowdMag app and share your magnetic data with scientists. You can also view the maps and graphs shared by other citizen scientists. Please send your feedback to

A quick tutorial on CrowdMag app usage

appstore Get it on Google Play


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