Moseley Wrought Iron Arch Bridge - North Andover, MA

A linear scale, also called a bar scale, scale bar, graphic scale, or graphical scale, is a means of visually showing the scale of a

map A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...

nautical chart A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land ( topographic map), natural features of the seabed, details of the co ...

engineering drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number o ...

, or architectural drawing. A scale bar is common element of map layouts. On large scale maps and charts, those covering a small area, and engineering and architectural drawings, the linear scale can be very simple, a line marked at intervals to show the distance on the earth or object which the distance on the scale represents. A person using the map can use a pair of dividers (or, less precisely, two fingers) to measure a distance by comparing it to the linear scale. The length of the line on the linear scale is equal to the distance represented on the earth multiplied by the map or chart's scale. In most projections, scale varies with

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...

, so on small scale maps, covering large areas and a wide range of latitudes, the linear scale must show the scale for the range of latitudes covered by the map. One of these is shown below. Since most nautical charts are constructed using the

Mercator projection The Mercator projection () is a cylindrical map projection presented by Flemish geographer and cartographer Gerardus Mercator in 1569. It became the standard map projection for navigation because it is unique in representing north as up and s ...

whose scale varies substantially with latitude, linear scales are not used on charts with scales smaller than approximately 1/80,000. Mariners generally use the

nautical mile A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude. Tod ...

, which, because a nautical mile is approximately equal to a minute of latitude, can be measured against the latitude scale at the sides of the chart. While linear scales are used on architectural and engineering drawings, particularly those that are drawn after the subject has been built, many such drawings do not have a linear scale and are marked "Do Not Scale Drawing" in recognition of the fact that paper size changes with environmental changes and only dimensions that are specifically shown on the drawing can be used reliably in precise manufacturing.

Nomenclature

The terms "bar scale", "graphic scale", "graphical scale", "linear scale", and "scale" are all used. '' Bowditch'' defined only "bar scale" in its 1962 Glossary, but added a reference to "graphic scale" by its 2002 edition. Dutton used both terms in 1978. The

International Hydrographic Organization The International Hydrographic Organization (IHO) is an intergovernmental organisation representing hydrography. , the IHO comprised 98 Member States. A principal aim of the IHO is to ensure that the world's seas, oceans and navigable waters ...

's ''Chart No. 1'' uses only "linear scale". The British Admiralty's ''Mariner's Handbook'' uses "scale" to describe a linear scale and avoids confusion by using "natural scale" for the fraction defined at

scale (map) The scale of a map is the ratio of a distance on the map to the corresponding distance on the ground. This simple concept is complicated by the curvature of the Earth's surface, which forces scale to vary across a map. Because of this variation ...

References

{{Reflist , refs= {{cite book, url=http://www.nauticalcharts.noaa.gov/mcd/chartno1.htm , title = Chart No. 1, Chart Number, Title, Marginal Notes , publisher= Jointly by NOAA and Department of Commerce, USA The cited book incorporates IHO Chart INT 1 and therefore represents the practice of the members of the IHO, most of the seafaring nations. {{cite book, last=Bowditch, first=Nathaniel, LLD, title=The American Practical Navigator, publisher=National Imagery and Mapping Agency, location=Washington, edition=2002, chapter=Glossary, url=http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Gloss-1.pdf, display-authors=etal, access-date=2010-11-16, archive-url=https://web.archive.org/web/20170517000124/http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Gloss-1.pdf, archive-date=2017-05-17, url-status=dead {{cite book, last=Bowditch, first=Nathaniel, LLD, title=The American Practical Navigator, publisher=National Imagery and Mapping Agency, location=Washington, edition=2002, pages=34–35, url=http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-03.pdf, display-authors=etal, access-date=2010-11-16, archive-url=https://web.archive.org/web/20120315020620/http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-03.pdf, archive-date=2012-03-15, url-status=dead {{cite book, last=Maloney, first=Elbert S., title=Dutton's Navigation & Piloting, publisher=Naval Institute Press, location=Annapolis, year=1978, edition=13th, pages=52–3 {{cite book, last=Bowditch, first=Nathaniel, LLD, title=The American Practical Navigator, publisher=U.S. Navy Hydrographic Office, location=Washington, edition=1962, chapter=Glossary, display-authors=etal Do a web search on "Do not scale drawing" to see many examples.
/ref> {{cite book, title=The Mariner's Handbook, editor=Lt. Cmdr. C.J. de C. Scott, R.N., publisher=The Hydrographer of the Navy, location=Taunton, year=1973, page=33 Cartography Technical drawing Scales

Nomenclature

See also

References