What are geomagnetic models?.
• 6a. What are magnetic field models and why do we need them? • Because the Earth’s magnetic field is constantly changing, it is impossible to accurately predict what the field will be at any point in the very distant future. By constantly measuring the magnetic field, we can observe how the field is changing over a period of years. Using this information, it is possible to create a mathematical representation of the Earth’s main magnetic field and how it is changing. Since the field changes the way it is changing, new observations must continually be made and models generated to accurately represent the magnetic field as it is. • 6b. How accurate are the magnetic field models? • The accuracy of a model in calculating the magnetic field influencing a compass or other magnetic sensor is affected by many things, including where you are using the compass. In general, the present day field models such as the IGRF and World Magnetic Model (WMM) are accurate to within 30 minutes of arc for D
