Term
| Map Projections: Graticule |
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Definition
| The arrangement of parallels and meridians draped over a spherical or ellipsoidal approximation of the earth. |
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Term
| Map Projections: Great Circle Vs. Small Circle |
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Definition
A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves (looks curved on mercator projection)[Meridians are great circles)
A small circle of a sphere is the circle constructed by a plane crossing the sphere not in its center. Small circles always have smaller diameters than the sphere itself (compare great circle). Small circles cannot be parallel, because parallelism doesn't exist in spherical geometry. By contrast, all meridians of longitude, paired with their opposite meridian in the other hemisphere, form great circles. |
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Term
| Map Projections: Rhumb Line |
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Definition
In navigation, a rhumb line (or loxodrome) is a line crossing all meridians of longitude at the same angle, i.e. a path derived from a defined initial bearing. That is, upon taking an initial bearing, one proceeds along the same bearing, without changing the direction as measured relative to true north.
Its use in navigation is directly linked to the style, or projection of certain navigational maps. A rhumb line appears as a straight line on a Mercator projection map.[1]
On a plane surface this would be the shortest distance between two points. Over the Earth's surface at low latitudes or over short distances it can be used for plotting a vehicle, aircraft or ship's course.[1] Over longer distances and/or at higher latitudes great circle routes provide the shortest distances. |
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Term
| Map Projections: Map Projection Surfaces |
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Definition
| A surface that can be unfolded or unrolled into a plane or sheet without stretching, tearing or shrinking is called a developable surface. The cylinder, cone and of course the plane are all developable surfaces. The sphere and ellipsoid are not developable surfaces. |
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Term
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Definition
is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. Each state contains one or more state plane zones, the boundaries of which usually follow county lines.
good because: 1)uses a simple Cartesian coordinate system to specify locations & 2)highly accurate within each zone
States that are long in the east-west direction are typically divided into zones that are also long east-west. These zones use the Lambert conformal conic projection, because it is good at maintaining accuracy along an east-west axis. Zones that are long in the north-south direction use the Transverse Mercator projection because it is better at maintaining accuracy along a north-south axis. |
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Term
| Universal Transverse Mercator Coordinates |
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Definition
Each of the 60 longitude zones in the UTM system is based on a transverse Mercator projection, which is capable of mapping a region of large north-south extent with a low amount of distortion.
The UTM system divides the surface of Earth between 80°S and 84°N latitude into 60 zones, each 6° of longitude in width and centered over a meridian of longitude. Zones are numbered from 1 to 60.
topo maps=On 1:24,000 maps, grid lines are spaced 1,000 meters apart. |
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Term
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Definition
In the first case (Mercator), the east-west scale always equals the north-south scale.
It became the standard map projection for nautical purposes because of its ability to represent lines of constant course, known as rhumb lines. |
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Term
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Definition
| How earth would appear from distant planet. Looks like a sphere. Remember pop bottle. |
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Term
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Definition
Used by USGS for many quadrangle maps at scales from 1:24,000 to 1:250,000; such maps can be joined at their edges only if they are in the same zone with one central meridian. Also used for mapping large areas that are mainly north–south in extent.
Distances are true only along the central meridian selected by the mapmaker or else along two lines parallel to it, but all distances, directions, shapes, and areas are reasonably accurate within 15° of the central meridian. Distortion of distances, directions, and size of areas increases rapidly outside the 15° band. Because the map is conformal, however, shapes and angles within any small area (such as that shown by a USGS topographic map) are essentially true.
Graticule spacing increases away from central meridian. Equator is straight. Other parallels are complex curves concave toward nearest pole.
Central meridian and each meridian 90° from it are straight. Other meridians are complex curves concave toward central meridian.
Presented by Lambert in 1772.
Cylindrical—Mathematically projected on cylinder tangent to a meridian. (Cylinder may also be secant.) |
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Term
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Definition
Used to represent the entire Earth in a rectangular frame. Popular for world maps. Looks like Mercator but is not useful for navigation. Shows poles as straight lines.
Avoids some of the scale exaggerations of the Mercator but shows neither shapes nor areas without distortion.
Directions are true only along the Equator. Distances are true only along the Equator. Distortion of distances, areas, and shapes is extreme in high latitudes.
Map is not equal area, equidistant, conformal or perspective.
Presented by O. M. Miller in 1942.
Cylindrical—Mathematically projected onto a cylinder tangent at the Equator. |
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Term
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Definition
Uses tabular coordinates rather than mathematical formulas to make the world "look right." Better balance of size and shape of high-latitude lands than in Mercator, Van der Grinten, or Mollweide. Soviet Union, Canada, and Greenland truer to size, but Greenland compressed.
Directions true along all parallels and along central meridian. Distances constant along Equator and other parallels, but scales vary. Scale true along 38° N & S, constant along any given parallel, same along N & S parallels same distance from. Equator. Distortion: All points have some. Very low along Equator and within 45° of center. Greatest near the poles.
Not conformal, equal area, equidistant, or perspective.
Used in Goode's Atlas, adopted for National Geographic's world maps in 1988, appears in growing number of other publications, may replace Mercator in many classrooms.
Presented by Arthur H. Robinson in 1963.
Pseudocylindrical or orthophanic ("right appearing") projection. |
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Term
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Definition
Used by USGS in the National Atlas of the United States of America™ and for large-scale mapping of Micronesia. Useful for showing airline distances from center point of projection. Useful for seismic and radio work. Oblique aspect used for atlas maps of continents and world maps for radio and aviation use. Polar aspect used for world maps, maps of polar hemispheres, and United Nations emblem.
Distances and directions to all places true only from center point of projection. Distances correct between points along straight lines through center. All other distances incorrect . Any straight line drawn through center point is on a great circle. Distortion of areas and shapes increases away from center point.
Azimuthal—Mathematically projected on a plane tangent to any point on globe. Polar aspect is tangent only at pole. |
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Term
| Lambert Azimuthal Equal Area |
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Definition
Used by the USGS in its National Atlas and Circum-Pacific Map Series. Suited for regions extending equally in all directions from center points, such as Asia and Pacific Ocean.
Areas on the map are shown in true proportion to the same areas on the Earth. Quadrangles (bounded by two meridians and two parallels) at the same latitude are uniform in area.
Directions are true only from center point. Scale decreases gradually away from center point. Distortion of shapes increases away from center point. Any straight line drawn through center point is on a great circle.
Map is equal area but not conformal, perspective, or equidistant.
Presented by Lambert in 1772.
Azimuthal—Mathematically projected on a plane tangent to any point on globe. Polar aspect is tangent only at pole. |
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Term
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Definition
| Distance, Shape, Direction, and Area. |
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Term
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Definition
Used by USGS for many 7.5- and 15-minute topographic maps and for the State Base Map series. Also used to show a country or region that is mainly east-west in extent.
One of the most widely used map projections in the United States today. Looks like the Albers Equal Area Conic, but graticule spacings differ.
Retains conformality. Distances true only along standard parallels; reasonably accurate elsewhere in limited regions. Directions reasonably accurate. Distortion of shapes and areas minimal at, but increases away from standard parallels. Shapes on large-scale maps of small areas essentially true.
Map is conformal but not perspective, equal area, or equidistant.
For USGS Base Map series for the 48 conterminous States, standard parallels are 33°N and 45°N (maximum scale error for map of 48 States is 2 ½%). For USGS Topographic Map series (7.5- and 15-minute), standard parallels vary. For aeronautical charts of Alaska, they are 55°N and 65°N; for the National Atlas of Canada, they are 49°N and 77°N.
Presented by Lambert in 1772.
Conic—Mathematically projected on a cone conceptually secant at two standard parallels. |
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Term
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Definition
study of place names (toponyms), their origins, meanings, use and typology
basically, the name of a location. |
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