Lunar Astronautical Chart (LAC)
The original meaning of the term Lunar Astronautical Chart is one of a series of maps of the Moon produced by the U.S. Air Force ACIC in the 1960's. The Moon was systematically divided into 144 "sheets" or zones (later called Regions by the IAU) and the features within each were portrayed on the basis of first telescopic, and later Lunar Orbiter images. The original printed maps measured 22x29 inches (56x73 cm), and portrayed the lunar topography in an airbrush "shaded relief" style at a scale of 1:1,000,000 (1 unit on map = 1,000,000 units on Moon; that is, 1 cm on map is ~10 km on Moon) with spot elevations and crater depths based on shadow lengths. Occasionally, 300 m contours were added as well. The maps represent aerial views of the Moon, but the projection used depends on the latitude zone. The background color varies to represent the brightness of the area at Full Moon. Features are labeled according to the then-current IAU nomenclature.
- The 144 sheet layout is said (Carder, 1962) to be "similar to the The International Map of the World," but it actually seems to quite different. The reference is apparently to the World Aeronautical Chart series, which was also at the 1:1,000,000 scale. - Jim Mosher
- Only 44 of the sheets were ever completed in the original LAC series -- about half the 84 needed to cover the hemisphere visible from Earth. They show the Moon's disk to about +/-65° in latitude and +/-50 to 70° in longitude. The USGS issued a corresponding geologic map for each of these regions, using the LAC map as a background, although they chose to number them differently. A handful of LAC regions were added, and a few were revised, in the DMA's later LM series, based on Apollo imagery.
- All 44 of the original LACs are available for download from the LPI website.
- The original project was intended to include only enough LAC's to map the Moon's equatorial zone, but was later extended to most of the nearside. For more information about the original LAC series see: History of the LAC maps
Other uses of the term
- The term "LAC" map has somewhat confusingly been adopted to designate maps prepared by other agencies and institutions, portraying the same zones with other imagery. - Jim Mosher
- I think of LACs as being both the original map series and a very specific way to divide the Moon into map-size pieces. It is very convenient to know that a LAC number covers the exact same area whether it is the original LAC maps from the 60s, later revisions in the 70s, the USGS geologic maps, or the Bussey and Spudis sheets in their Clementine Atlas. This is exactly analogous to what we do on Earth. The USGS has a variety of map series, including a widely used 1:1,000,000 set. If a user knows the topo map number of their area of interest, that same series number commonly allows rapid identification of maps of the same area but showing different types of information (aerial photography, water quality, climate variations, etc). Long live LACs! - tychocrater Aug 16, 2007
- The LAC sheet system was also adopted for the USGS Digital Atlas, which illustrates the IAU-approved lunar nomenclature for all 144 Regions on Lunar Orbiter and Shaded Relief-topographic backgrounds called "LAC"s.
- Carder, R. W. 1962. Lunar Charting on a Scale of 1:1000000. In: The Moon, (Kopal, Z., and Mikhailov, Z. K., editors) IAU Symposium 14, Academic Press, pp. 117-129. (detailed information on how the first LAC's were produced)
- Kopal, Zdenek; Carder, Robert W. 1974. Mapping of the moon. Past and present. Astrophysics and Space Science Library, Dordrecht: Reidel.
- LAC map on display at the Linda Hall Library