Even at the nose, many factors can affect the relationship between the local AOA and true wing AOA (fig. 9). The angle of airflow around the nose is not the same as at the wing. Also, the sensitivity to changes in AOA is greater, so a 1-deg change in true wing AOA causes a local flow change at the nose of 1.5 to 2 deg.
Other nations' maps often use coordinates computed assuming the Earth is a completely different size and shape from what the Department of Defense uses, but we have to be ready to fight around the world. US forces now use a datum called World Geodetic System 1984, or WGS 84. The National Imagery and Mapping Agency (NGA) produces all of its new maps with this system. Unfortunately, we reprint many of our maps from products made by allied countries that use local datums.
Establishment Process Steps. 1  Decode the feature control frame. 2  Identify the datum features. 3  Construct the datum feature simulators. 4  Extract the datums from the simulators. 5  Use the datums to constrain a starter coordinate system in the simulators, thereby turning it into the sought after datum reference frame.