Essential feature builder vocabulary (Defense Mapping)
The horizontal direction to or from any point, usually measured clockwise from true north, magnetic north, or some other reference point through 360 degrees.
The magnetic declination is the angular difference between True North and magnetic north, which changes over time.
Magnetic variation value
The magnetic variation value is determined based on the source defined in the MagVar Source parameter. Depending on the source selected, this can be a predefined value or a value you determine.
Magnetic variation source
The magnetic variation source value is defined in the MagVar Source parameter for the function you are using. Possible sources for the magnetic variation value are as follows:
- Unknown—The source is unknown; you define the magnetic variation value.
- None—There is no source for the magnetic variation value; you define the value.
- User Input—You define the magnetic variation value.
- Source Field—The value is populated from an attribute value.
- Magnetic Model—The magnetic variation value is populated from the WMM2005 utility.
Magnetic variation year
This is the year that corresponds with the magnetic declination value if you choose to use the World Magnetic Model as the source. The World Magnetic Model has values for 2005 through 2015.