org.geotools.referencing.operation.transform
Class NADCONTransform

Object
  extended by Formattable
      extended by AbstractMathTransform
          extended by NADCONTransform
All Implemented Interfaces:
Serializable, MathTransform, MathTransform2D

public class NADCONTransform
extends AbstractMathTransform
implements MathTransform2D, Serializable

Transform backed by the North American Datum Conversion grid. The North American Datum Conversion (NADCON) Transform (EPSG code 9613) is a two dimentional datum shift method, created by the National Geodetic Survey (NGS), that uses interpolated values from two grid shift files. This method is used to transform NAD27 (EPSG code 4267) datum coordinates (and some others) to NAD83 (EPSG code 4267) within the United States. There are two set of grid shift files: NADCON and High Accuracy Reference Networks (HARN). NADCON shfts from NAD27 (and some others) to NAD83 while HARN shifts from the NADCON NAD83 to an improved NAD83. Both sets of grid shift files may be downloaded from www.ngs.noaa.gov/PC_PROD/NADCON/.

Some of the NADCON grids, their areas of use, and source datums are shown in the following table.

Shift File NameAreaSource DatumAccuracy at 67% confidence (m)
CONUSConterminous U S (lower 48 states)NAD270.15
ALASKAAlaska, incl. Aleutian IslandsNAD270.5
HAWAIIHawaiian IslandsOld Hawaiian (4135)0.2
STLRNCSt. Lawrence Is., AKSt. Lawrence Island (4136)--
STPAUL St. Paul Is., AKSt. Paul Island (4137)--
STGEORGESt. George Is., AKSt. George Island (4138)--
PRVIPuerto Rico and the Virgin IslandsPuerto Rico (4139)0.05

Grid shift files come in two formats: binary and text. The files from the NGS are binary and have .las (latitude shift) and .los (longitude shift) extentions. Text grids may be created with the NGS nadgrd program and have .laa (latitude shift) and .loa (longitude shift) file extentions. Both types of files may be used here.

The grid names to use for transforming are parameters of this MathTransform. This parameter may be the full name and path to the grids or just the name of the grids if the default location of the grids was set as a preference. This preference may be set with the main method of this class.

Transformations here have been tested to be within 0.00001 seconds of values given by the NGS ndcon210 program for NADCON grids. American Samoa and HARN shifts have not yet been tested. References:

Since:
2.1
Author:
Rueben Schulz
See Also:
NADCON - North American Datum Conversion Utility, Serialized Form

Nested Class Summary
static class NADCONTransform.Provider
          The provider for NADCONTransform.
 
Field Summary
 
Fields inherited from class Formattable
SINGLE_LINE
 
Constructor Summary
NADCONTransform(URI latGridName, URI longGridName)
          Constructs a NADCONTransform from the specified grid shift files.
 
Method Summary
 boolean equals(Object object)
          Compares the specified object with this math transform for equality.
 ParameterDescriptorGroup getParameterDescriptors()
          Returns the parameter descriptors for this math transform.
 ParameterValueGroup getParameterValues()
          Returns the parameter values for this math transform.
 int getSourceDimensions()
          Gets the dimension of input points (always 2).
 int getTargetDimensions()
          Gets the dimension of output points (always 2).
 int hashCode()
          Returns a hash value for this transform.
 MathTransform2D inverse()
          Returns the inverse of this transform.
 void inverseTransform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts)
          Transforms nad83 values to nad27.
protected  URL locateGrid(URI uri)
           
static void main(String[] args)
          Used to set the preference for the default grid shift file location.
 void transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts)
          Transforms a list of coordinate point ordinal values.
 
Methods inherited from class AbstractMathTransform
createTransformedShape, derivative, derivative, ensureNonNull, formatWKT, getName, isIdentity, needCopy, rollLongitude, transform, transform, transform, transform, transform
 
Methods inherited from class Formattable
cleanupThreadLocals, toString, toWKT, toWKT, toWKT, toWKT
 
Methods inherited from class Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface MathTransform2D
createTransformedShape, derivative, transform
 
Methods inherited from interface MathTransform
derivative, isIdentity, toWKT, transform, transform, transform, transform
 

Constructor Detail

NADCONTransform

public NADCONTransform(URI latGridName,
                       URI longGridName)
                throws ParameterNotFoundException,
                       FactoryException
Constructs a NADCONTransform from the specified grid shift files.

Parameters:
latGridName - path and name (or just name if GRID_LOCATION is set) to the latitude difference file. This will have a .las or .laa file extention.
longGridName - path and name (or just name if GRID_LOCATION is set) to the longitude difference file. This will have a .los or .loa file extention.
Throws:
ParameterNotFoundException - if a math transform parameter cannot be found.
FactoryException - if there is a problem creating this math transform (ie file extentions are unknown or there is an error reading the grid files)
Method Detail

locateGrid

protected URL locateGrid(URI uri)
                  throws FactoryException
Throws:
FactoryException

getParameterDescriptors

public ParameterDescriptorGroup getParameterDescriptors()
Returns the parameter descriptors for this math transform.

Overrides:
getParameterDescriptors in class AbstractMathTransform
Returns:
The parameter descriptors for this math transform, or null.
See Also:
OperationMethod.getParameters()

getParameterValues

public ParameterValueGroup getParameterValues()
Returns the parameter values for this math transform.

Overrides:
getParameterValues in class AbstractMathTransform
Returns:
A copy of the parameter values for this math transform.
See Also:
Operation.getParameterValues()

getSourceDimensions

public int getSourceDimensions()
Gets the dimension of input points (always 2).

Specified by:
getSourceDimensions in interface MathTransform
Specified by:
getSourceDimensions in class AbstractMathTransform
Returns:
the source dimensions.

getTargetDimensions

public int getTargetDimensions()
Gets the dimension of output points (always 2).

Specified by:
getTargetDimensions in interface MathTransform
Specified by:
getTargetDimensions in class AbstractMathTransform
Returns:
the target dimensions.

transform

public void transform(double[] srcPts,
                      int srcOff,
                      double[] dstPts,
                      int dstOff,
                      int numPts)
               throws TransformException
Transforms a list of coordinate point ordinal values. This method is provided for efficiently transforming many points. The supplied array of ordinal values will contain packed ordinal values. For example, if the source dimension is 3, then the ordinals will be packed in this order: (x0,y0,z0, x1,y1,z1 ...). All input and output values are in decimal degrees.

Specified by:
transform in interface MathTransform
Parameters:
srcPts - the array containing the source point coordinates.
srcOff - the offset to the first point to be transformed in the source array.
dstPts - the array into which the transformed point coordinates are returned. May be the same than srcPts.
dstOff - the offset to the location of the first transformed point that is stored in the destination array.
numPts - the number of point objects to be transformed.
Throws:
TransformException - if the input point is outside the area covered by this grid.

inverseTransform

public void inverseTransform(double[] srcPts,
                             int srcOff,
                             double[] dstPts,
                             int dstOff,
                             int numPts)
                      throws TransformException
Transforms nad83 values to nad27. Input and output values are in decimal degrees. This is done by itteratively finding a nad27 value that shifts to the input nad83 value. The input nad83 value is used as the first approximation.

Parameters:
srcPts - the array containing the source point coordinates.
srcOff - the offset to the first point to be transformed in the source array.
dstPts - the array into which the transformed point coordinates are returned. May be the same than srcPts.
dstOff - the offset to the location of the first transformed point that is stored in the destination array.
numPts - the number of point objects to be transformed.
Throws:
TransformException - if the input point is outside the area covered by this grid.

inverse

public MathTransform2D inverse()
Returns the inverse of this transform.

Specified by:
inverse in interface MathTransform
Specified by:
inverse in interface MathTransform2D
Overrides:
inverse in class AbstractMathTransform
Returns:
the inverse of this transform

hashCode

public int hashCode()
Description copied from class: AbstractMathTransform
Returns a hash value for this transform.

Overrides:
hashCode in class AbstractMathTransform

equals

public boolean equals(Object object)
Description copied from class: AbstractMathTransform
Compares the specified object with this math transform for equality. The default implementation checks if object is an instance of the same class than this and use the same parameter descriptor. Subclasses should override this method in order to compare internal fields.

Overrides:
equals in class AbstractMathTransform
Parameters:
object - The object to compare with this transform.
Returns:
true if the given object is a transform of the same class and if, given identical source position, the transformed position would be the equals.

main

public static void main(String[] args)
Used to set the preference for the default grid shift file location. This allows grids parameters to be specified by name only, without the full path. This needs to be done only once, by the user. Path values may be simple file system paths or more complex text representations of a url. A value of "default" resets this preference to its default value.

Example:

 java org.geotools.referencing.operation.transform.NADCONTransform file:///home/rschulz/GIS/NADCON/data
 

Parameters:
args - a single argument for the defualt location of grid shift files


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