![]() ![]() The size of this difference for a particular map depends on the projection and the map location relative to the projection origin. The difference between true north and grid north is an inherent effect of transforming the earth's spherical surface to a plane surface. Historical topographic maps might relate grid north to other grid systems. A map is a symbolic representation of an actual element or an area on a flat surface. Shallow water is usually depicted as a deeper blue color whereas deeper water is depicted as a lighter blue on maps. ![]() All US Topo maps have a 1,000-meter UTM grid included on the map the angle at which this grid meets the map projection line visually shows the difference between true and grid north. Road maps, politic maps, and cadaster maps are a few different types of maps. My three standard map types: custom detailed maps on 11 x 17 paper, a commercial overview map, and digital maps and layers on a smartphone. On current US Topo maps, the projection is Transverse Mercator and the plane grid is Universal Transverse Mercator (UTM). Read the full series: Part 1: Introduction. Grid north (GN) is the direction of a plane grid system, usually the grid associated with the map projection. Magnetic declination values shown on current maps are obtained from NOAA's National Geophysical Data Center. The direction of magnetic north varies over time and with the position on the earth's surface, so magnetic declination values on old maps might no longer be accurate. Magnetic north (MN) shows the direction a magnetic compass would point at the time the map was published. The star symbol in the diagram indicates true north. All longitude lines converge to points at the north and south poles. ![]() True north, also called geodetic north or geographic north, is the direction of the line of longitude that bisects the quadrangle. Star is True north, GN is Grid north, MN is Magnetic north. Included in The National Map are the latest elevation data from the 3D Elevation Program (3DEP), surface water data from the National Hydrography Datasets (NHD), and place name data from the. Example of north arrows from US Topo map. The National Map is a collection of free, nationally-consistent geographic datasets that describe the landscape of the United States and its territories. ![]()
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