JOG (Joint Operational Graphic) - 1:250,000 Scale
The Joint Operational Graphic topographic series were produced by the American military for use in combined operations by ground and air forces. These maps are compiled to conform to international US Defense Mapping Agency (DMA) specification MIL-J-89100. Between 84° N and 80° S the Transverse Mercator Projection is used. On the poles (between 84° - 90° N and between 80° - 90° S) the Polar Stereographic Projection is used. The contour interval varies between 50 m and 100 m depending on the particular series (1501 or 1502).
The JOG maps are probably the most useful out of the options in the article for overland trips - a 1:250,000 scale is about perfect for driving conditions, particularly if moving map software with a GPS is being used.
TPC (Tactical Pilotage Chart) - 1:500,000 Scale
These charts are identical to the ONCs below but produced at 1:500,000 scale, and designed for pilots flying less than 500 ft. Charts are numbered in quadrant subdivisions of the ONC compilation in clockwise rotation, i.e. starting at the northwest corner ONC A-1 would be named TPC A-1A, then to the northeast TPC A-1B, southeast TPC A-1C, and finally southwest TPC A-1D. The map Projection is Lambert Conformal Conic based on standard parallels 5 degrees, 20 minutes apart. Miltary standard MIL-T-89101 details the actual parallels and convergence factors. Charts located over the poles (i.e. between 80 and 90 degrees north and south) are produced with Polar Stereographic Projection.
ONC (Operational Navigation Chart) - 1:1,000,000 Scale
Operational Navigation Charts (ONCs) are topographic maps produced by the American Defence Mapping Agency at 1:1,000,000 scale. They are designed for pilots flying at 2,000 to 25,000 ft, and are used to help identify terrain and cultural objects both visually and by radar. The detail is limited so that a pilot, flying at high speeds, can quickly glance at a chart and recognize a major feature and associate it with the object in view through the cockpit window. They are numbered as ONC A-1, ONC A-2, etc. The projection is the same as the TPC series above. These maps are produced under US military standard MIL-O-89102.
JNC (Jet Navigation Chart) - 1:2,000,000 Scale
Jet Navigation Charts are designed for radar navigation, high altitude bombing, mission planning, as well as visual navigation.
GNC (Global Navigation & Planning Chart) - 1:5,000,000 Scale
The US Defense Supply Center writes that the Global Navigation Chart series were designed to support
air operations requiring long range, high speed, high altitude aerospace navigation; specifically, transports, tankers, and long-range bombers. Primary information on the GNC identifies vertical obstructions to flight, aid navigation features, and landing options.
Interesting, but clearly at 1:5,000,000 scale, these maps are not suitable for much other than classroom instruction or maybe nice wall hangings - I certaintly wouldn't try to use these to navigate on an expedition!
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I am interested in the copyright of the TPC charts. Are there any restrictions on their re-use for other projects, e.g. as a source for a GIS project?
Peter, every map will be different, subject to the limitations typically shown on the map border. The only 1:500,000 scale maps I believe are in the public domain are the Russian Military TPC charts.
The Nima site has TPC and ONC in digital form for N.China with free download. I downloaded good coverage but now find that each download attempt is met by the file is not available message.Contacting NIma via their contact us option doesn’t seem to work. Any ideas?