CrowdMag Tutorial

CrowdMag is a citizen science project that uses your mobile phone’s internal magnetometer to record magnetic data as you move. Anonymous data collected through the application can be used to detect magnetic anomalies caused by objects in the surrounding environment which help inform NOAA science.

You can explore the data you collect and see if you can match up magnetic anomalies with objects in your environment. Learn more about Earth's magnetic fields from the NOAA Geomagnetism group.

Instructions

Review the following step-by-step instructions before using the CrowdMag app to collect data.

Step 1: Download

Download the CrowdMag mobile application from Google Play or the Apple App Store.

Crowdmag download preview in the Apps store.

Step 2: Record

Open the application and tap “Record” then "Walking" to begin recording your “magtivity.” It is best to do this outside while you move around. “Magtivity” is a magnetic activity recording that uses your phone’s internal magnetometer to measure the magnetic field of an area.

"Record" and "Walking" buttons in the CrowdMag app.

Step 3: Collect

Make sure to hold your phone out during the magtivity. Watch the data come in as you move around.

Image of a person's hand holding a phone a phone in front of them effectively record data on the CrowdMag app while they walk. — Don't forget to hold your phone in front of you to collect data after you start recording!

Step 4: Observe

Pay attention as you approach large metal objects (like bridges) to see how they change the color of your path. Different colors show changes in magnetic field readings.

Metal objects (like bridges) on your route can change magnetic field readings.

Step 5: Pause and Filter

When finished recording the magtivity, tap “Pause.” Then tap “Filter” to remove any noisy (or unexpected) data. These data will still be sent to NOAA, but will make your data visualization look cleaner.

The "Pause" button is in the lower right-hand corner of the mobile app.

Step 6: Save

Save the event with a unique name for later reference. After you tap “Save,” the data will be sent to NOAA to help with our science!

Don't forget to save your magtivity after you stop recording!

Step 7: Review

After recording, tap each dot to see the magnetic data. Blue dots indicate areas with a lower magnetic field value. Red dots indicate a higher magnetic field value. If dot colors are consistent, there aren’t any magnetic disturbances. Do red and blue dots correlate with objects in the area, such as a bridge, pipe, or powerline?

Dots on the map contain magnetic fied readings.

Step 8: Export

Tap “Settings,” then “Export my data” to export your data. You can email the data in a CSV format. You might want to email it to yourself or a friend so you can analyze it yourself (for example, read it into Microsoft Excel or Google Sheets).