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83 lines
4.3 KiB
C++
83 lines
4.3 KiB
C++
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/*!
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\defgroup projections projections: Projections
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\brief Projections are algorithms to transform earth coordinates (latlong coordinates, sphere coordinates,
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coordinates in latitude longitude) to a cartesian system. Algorithms here are converted from PROJ4 (http://trac.osgeo.org/proj)
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\details Almost all projection sources are converted from PROJ4, from C to a C++ template structure.
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PROJ4 is originally written by Gerald Evenden (then of the USGS).
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Projections can be used in combination with the Generic Geometry Library.
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Because it does not use the Generic Geometry Library,
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it might also be used as a standalone map projection library.
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\par Projection parameters
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(This list is adapted from the PROJ4 documentation.)
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- \b proj is required for selection of the cartographic transformation
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function and where name is an acronym for the desired projection.
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- \b R specifies that the projection should be computed as a spherical Earth
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with radius R.
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- \b ellps The \b ellps option allows selection of standard, predefined
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ellipsoid figures. For spherical only projections, the major axis is used as the
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radius.
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- \b a specifies an elliptical Earth’s major axis a.
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- \b es defines the elliptical Earth’s squared eccentricity. Optionally,
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either \b b, \b e, \b rf or \b f may be used where \b b, \b e and \b f are respective minor axis,
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eccentricity and flattening and \b rf = 1/f
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- \b R_A must be used with elliptical Earth parameters. It determines that spherical
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computations be used with the radius of a sphere that has a surface area
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equivalent to the selected ellipsoid.
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- \b R_V can be used in a similar manner for sphere radius of an ellipse with equivalent volume.
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- \b R_a must be used with elliptical Earth parameters. Spherical radius of the
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arithmetic mean of the major and minor axis is used.
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- \b R_g and \b R_h can be used for equivalent geometric and harmonic means of major and minor axis.
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- \b R_lat_a must be used with elliptical Earth parameters. Spherical radius
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of the arithmetic mean of the principle radii of the ellipsoid at latitude is used.
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- \b R_lat_g can be used for equivalent geometric mean of the principle radii.
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- \b x_0 false easting; added to x value of the cartesian coordinate. Used in
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grid systems to avoid negative grid coordinates.
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- \b y_0 false northing; added to y value of the cartesian coordinate. See x_0.
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- \b lon_0 central meridian. Along with lat_0, normally determines the
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geographic origin of the projection.
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- \b lat_0 central parallel. See lon_0.
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- \b units selects conversion of cartesian values to units specified by name.
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When used, other + metric parameters must be in meters.
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- \b geoc data geographic coordinates are to be treated as geocentric when this
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option specified.
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- \b over inhibit reduction of input longitude values to a range within ±180 of the central meridian.
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\note
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- Note that many projections have also their own parameters, additionally to the list above
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- Note also that some of the parameters above are required for some projections, others are always optionally
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\par Original copyright of PROJ4:
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- Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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- The above copyright notice and this permission notice shall be included
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in all copies or substantial portions of the Software.
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- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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DEALINGS IN THE SOFTWARE.
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*/
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/*!
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\defgroup projection projection: Projection struct's, classes
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\brief Projection struct's, classes
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\details
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*/
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/*
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- +init=file:key names a file containing cartographic control parameters associated
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with the keyword key.
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*/
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