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java.lang.Object org.geotools.referencing.wkt.Formattable org.geotools.referencing.operation.transform.AbstractMathTransform org.geotools.referencing.operation.projection.MapProjection org.geotools.referencing.operation.projection.Stereographic
Stereographic Projection. The directions starting from the central point are true, but the areas and the lengths become increasingly deformed as one moves away from the center. This projection is used to represent polar areas. It can be adapted for other areas having a circular form.
This implementation, and its subclasses, provides transforms for six cases of the stereographic projection:
"Oblique_Stereographic"
(EPSG code 9809), alias "Double_Stereographic"
in ESRI software"Stereographic"
in ESRI software (NOT EPSG code 9809)"Polar_Stereographic"
(EPSG code 9810, uses a series calculation for the inverse)"Polar Stereographic (variant B)"
(EPSG code 9829, uses a series calculation for the inverse)"Stereographic_North_Pole"
in ESRI software (uses itteration for the inverse)"Stereographic_South_Pole"
in ESRI software (uses itteration for the inverse)"Oblique_Stereographic"
and "Stereographic"
projections are "double" projections involving two parts: 1) a conformal
transformation of the geographic coordinates to a sphere and 2) a spherical
Stereographic projection. The EPSG considers both methods to be valid, but
considers them to be a different coordinate operation methods.
The "Stereographic"
case uses the USGS equations of Snyder.
This employs a simplified conversion to the conformal sphere that computes
the conformal latitude of each point on the sphere.
The "Oblique_Stereographic"
case uses equations from the EPSG.
This uses a more generalized form of the conversion to the conformal sphere; using only
a single conformal sphere at the origin point. Since this is a "double" projection,
it is sometimes called the "Double Stereographic". The "Oblique_Stereographic"
is used in New Brunswick (Canada) and the Netherlands.
The "Stereographic"
and "Double Stereographic"
names are used in
ESRI's ArcGIS 8.x product. The "Oblique_Stereographic"
name is the EPSG name
for the later only.
WARNING: Tests points calculated with ArcGIS's "Double Stereographic" are
not always equal to points calculated with the "Oblique_Stereographic"
.
However, where there are differences, two different implementations of these equations
(EPSG guidence note 7 and libproj) calculate the same values as we do. Until these
differences are resolved, please be careful when using this projection.
If a "latitude_of_origin"
parameter is supplied and is not consistent with the
projection classification (for example a latitude different from ±90? for the polar case),
then the oblique or polar case will be automatically inferred from the latitude. In other
words, the latitude of origin has precedence on the projection classification. If ommited,
then the default value is 90?N for "Polar_Stereographic"
and 0? for
"Oblique_Stereographic"
.
Polar projections that use the series equations for the inverse calculation will be little bit faster, but may be a little bit less accurate. If a polar "latitude_of_origin" is used for the "Oblique_Stereographic" or "Stereographic", the itterative equations will be used for inverse polar calculations.
The "Polar Stereographic (variant B)", "Stereographic_North_Pole", and "Stereographic_South_Pole" cases include a "standard_parallel_1" parameter. This parameter sets the latitude with a scale factor equal to the supplied scale factor. The "Polar Stereographic (variant B)" recieves its "latitude_of_origin" paramater value from the hemisphere of the "standard_parallel_1" value.
References:
Nested Class Summary  
static class 
Stereographic.Provider_North_Pole
The MathTransformProvider
for a Stereographic North Polar projection. 
static class 
Stereographic.Provider_Oblique
The MathTransformProvider
for a Stereographic Oblique projection. 
static class 
Stereographic.Provider_Polar_A
The MathTransformProvider
for a Stereographic Polar projection. 
static class 
Stereographic.Provider_Polar_B
The MathTransformProvider
for a Stereographic Polar (Variant B) projection. 
static class 
Stereographic.Provider_South_Pole
The MathTransformProvider
for a Stereographic North Polar projection. 
static class 
Stereographic.Provider_USGS
The MathTransformProvider
for a Stereographic (USGS equations) projection. 
Nested classes inherited from class org.geotools.referencing.operation.projection.MapProjection 
MapProjection.AbstractProvider 
Field Summary  
protected static short 
EPSG
Projection mode for switch statement. 
protected static short 
POLAR_A
Projection mode for switch statement. 
protected static short 
POLAR_B
Projection mode for switch statement. 
protected static short 
POLAR_NORTH
Projection mode for switch statement. 
protected static short 
POLAR_SOUTH
Projection mode for switch statement. 
protected short 
stereoType
The type of stereographic projection, used for wkt parameters. 
protected static short 
USGS
Projection mode for switch statement. 
Fields inherited from class org.geotools.referencing.operation.projection.MapProjection 
centralMeridian, excentricity, excentricitySquared, falseEasting, falseNorthing, globalScale, isSpherical, latitudeOfOrigin, scaleFactor, semiMajor, semiMinor 
Method Summary  
org.opengis.parameter.ParameterDescriptorGroup 
getParameterDescriptors()
Returns the parameter descriptors for this map projection. This is used for a providing a default implementation of MapProjection.getParameterValues() , as well as arguments checking. 
Methods inherited from class org.geotools.referencing.operation.projection.MapProjection 
equals, getParameterValues, getSourceDimensions, getTargetDimensions, getToleranceForAssertions, hashCode, inverse, inverseTransformNormalized, transform, transform, transform, transformNormalized 
Methods inherited from class org.geotools.referencing.operation.transform.AbstractMathTransform 
createTransformedShape, derivative, derivative, ensureNonNull, formatWKT, getDimSource, getDimTarget, isIdentity, needCopy, rollLongitude, transform 
Methods inherited from class org.geotools.referencing.wkt.Formattable 
toString, toWKT, toWKT, toWKT 
Methods inherited from class java.lang.Object 
clone, finalize, getClass, notify, notifyAll, wait, wait, wait 
Methods inherited from interface org.opengis.referencing.operation.MathTransform2D 
createTransformedShape, derivative 
Methods inherited from interface org.opengis.referencing.operation.MathTransform 
derivative, isIdentity, toWKT, transform 
Field Detail 
protected static final short EPSG
protected static final short USGS
protected static final short POLAR_A
protected static final short POLAR_B
protected static final short POLAR_NORTH
protected static final short POLAR_SOUTH
protected short stereoType
Method Detail 
public org.opengis.parameter.ParameterDescriptorGroup getParameterDescriptors()
MapProjection.getParameterValues()
, as well as arguments checking.
getParameterDescriptors
in class MapProjection


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