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Digital Elevation Models, for example, have often been created not from new remote sensing data but from existing paper topographic maps. Many government and private publishers use the artwork (especially the contour lines) from existing topographic map sheets as the basis for their own specialized or updated topographic maps.
1913 saw the beginning of the International Map of the World initiative, which set out to map all of Earth's significant land areas at a scale of 1:1 million, on about one thousand sheets, each covering four degrees latitude by six or more degrees longitude. Excluding borders, each sheet was 44 cm high and (depending on latitude) up to 66 cm wide.
Maps are useful in presenting key facts within a geographical context and enabling a descriptive overview of a complex concept to be accessed easily and quickly. WikiProject Maps encourages the creation of free maps and their upload on Wikimedia Commons. On the project's pages can be found advice, tools, links to resources, and map conventions.
The term is generally applied to any item used to mark a point as an elevation reference. Frequently, bronze or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point. If an elevation is marked on a map, but there is no physical mark on the ground, it is a spot height.
Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, [1] for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage.
A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes. [4] The contour interval of a contour map is the difference in elevation between successive contour lines. [5] The gradient of the function is always perpendicular to the contour ...
The grade (US) or gradient (UK) (also called stepth, slope, incline, mainfall, pitch or rise) of a physical feature, landform or constructed line is either the elevation angle of that surface to the horizontal or its tangent. It is a special case of the slope, where zero indicates horizontality. A larger number indicates higher or steeper ...
Before the end of the same year, a 1-arc second global digital elevation model (30 meters) was released. Most parts of the world have been covered by this dataset ranging from 54°S to 60°N latitude except for the Middle East and North Africa area. [17] Missing coverage of the Middle East was completed in August 2015. [19]