The World Magnetic Model (WMM), standard for navigation, is updated every five years to address changes in Earth’s magnetic field. The WMM was updated on December 17, 2024; WMM2025 is the most current version and will remain valid until late 2029.
The WMM file (WMM.COF) stored in MCS-enabled services is used to calculate the current compass rose values for magnetic variation (MAGVAR) point features when the compass rose display property is enabled. If the WMM.COF file is outdated, the values from the MAGVAR point feature are used instead.
To update the WMM used in your deployment of Maritime server, download the current version (WMM2025 (2025-2029) coefficients) and replace the WMM.COF file in the controlfiles folder of your deployment configuration. An example of the deployment location is:
C:\arcgisserver\directories\maritimeserver\maritimechartservice\controlfiles
Once the file is updated all MCS-enabled services must be restarted.
Learn more about configuring Maritime server
For more information regarding this update, please email maritime@esri.com.
