Horizontal position representation in the context of "Synoptic scale meteorology"

The North American Datum (NAD) is the horizontal datum used to define latitude and longitude (horizontal coordinates) in North America. A datum is a formal description of the shape of the Earth along with survey markers serving as "anchor" points for the coordinate system. In surveying, cartography, and land-use planning, two North American Datums are in use: the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). Both are geodetic reference systems based on slightly different assumptions and measurements.

Vertical measurements, based on distances above or below Mean High Water (MHW), are calculated using the North American Vertical Datum of 1988 (NAVD 88).

The Universal Transverse Mercator (UTM) is a projected coordinate system based on the transverse Mercator map projection of the Earth spheroid. As a map projection, it transforms geographic coordinates of locations on Earth's surface to assign plane coordinates to them. It is a horizontal position representation, which means it ignores altitude and treats the earth surface as an oblate ellipsoid. The system divides Earth into 60 zones and projects each to the plane as a basis for its coordinates. Specifying a location means specifying the zone and the x, y coordinate in that plane.

UTM parameter specifications vary by nation or region or mapping system. However, most zones in UTM span 6 degrees of longitude, and each has a designated central meridian. In each zone, the scale factor at the central meridian is specified to be 0.9996 of true scale (for most UTM systems in use). Therefore maps, atlases, and topographic grid systems built from an appropriate collection of UTM zones cover a region with planar maps with well-controlled, minimal distortion. For this reason, UTM coordinates are used in many nations and regions for topographic mapping, as well as more generally for pinpointing locations.