Tips for using calculators
Data entry values
Tips for entering data values for the magnetic declination and magnetic field calculators:
- Date (year,month,day)
Date may be entered by using the pull-down menus. The model is valid between the years 1900 and 2015. An updated model is expected to be implemented by January 2015.
- Latitude, Longitude
When entering latitude or longitude use one of the following two conventions:
- Decimal degrees to a maximum of three decimal places, e.g., 45.738; leave the minutes box blank. Choose North or South, East or West from the 'radio' buttons.
- Degrees and minutes; enter degrees in the first box; enter minutes to a maximum of one decimal place in the second box; e.g. 45 54.3. Choose North or South, East or West from the 'radio' buttons.
If you do not know your latitude and longitude consult one of the following sites:
- For locations within Canada:
- Gazeteer Map Service (Atlas of Canada)
- For locations outside Canada:
Geomagnetic reference field
The International Geomagnetic Reference Field is used to compute values within Canada and elsewhere in the world. Magnetic reference field models give results that are typically accurate to about 30 minutes of arc, but the difference between the model value and the true value of the magnetic field at a given location is dependent on a number of factors:
- The accuracy of the model will worsen at locations close to the magnetic poles.
- As the time from the epoch of the model increases, uncertainties in the estimate of secular variation will result in an increasingly large difference.
- Magnetic minerals in local geological formations cause magnetic anomalies that can sometimes be very large. These cannot be reproduced by reference field models.
- Large magnetic storms can temporarily cause large changes in the magnetic field, especially at high latitudes.