Custom Coordinate System (Projection) Presets

Manifold includes a huge number of projections in the Projections pane. Each projection is really the definition of a coordinate system. Many coordinate systems are defined by standard formulas in which given parameters may be varied to create a specific coordinate system. Many projections such as various national grids are simply specific parameterized variants of a general projection that has been given a local name. A specific parameterized variant of a coordinate system in Manifold is called a preset.

 

Although fundamentally new types of coordinate systems cannot be added since these involve the creation of new program logic, users can add new variations of coordinate systems by providing named presets for customized versions of the standard projections within Manifold that do accept parameters.

 

The definitions of coordinate systems available to Manifold are loaded from .xml files found in the Config folder. If desired, users can add their own variations to incorporate "new projections" into Manifold. An example of a new projection preset is:

 

<xml>

 <preset>

  <name>My System</name>

  <category>National Grids*My Country</category>

  <system>Cassini</system>

  <centerLat>31.73</centerLat>

  <centerLon>35.21</centerLon>

  <falseEasting>170000</falseEasting>

  <falseNorthing>126800.</falseNorthing>

 </preset>

</xml>

 

The <system> attribute specifies the base coordinate system that is being customized. Different coordinate systems allow different attributes. The above example shows attributes that can be used with the Cassini coordinate system.

 

Rules

 

·      There can be any number of <preset></preset> entries within a single XML file between the <xml> tag at the beginning of the file and the </xml> tag at the end of the file.

·      The name string supplied in the <name> attribute is mandatory and must be unique.

·      <category> is mandatory and represents the hierarchical path to the preset within the Projections dialog projections pane. Different levels of the hierarchical path are separated by an asterisk. For example, the preset above will appear within the National Grids folder in a My Country folder.

·      <system> is mandatory and is the name of an existing Manifold coordinate system.

·      Other attributes are parameters specific to the coordinate system, as listed below.

 

To utilize newly created or modified presets place the new or modified .xml file containing the presets into the Config folder for Manifold (normally C:\Program Files\Manifold System Professional\Config) and restart Manifold.

 

When Manifold launches, the system will scan all .xml files in the Config folder. Any <preset></preset> entries found in any of those .xml files will be loaded into the system as available presets.

 

Note: in the tables listing tags below, such as those that may be used for parameters, it is understood that a <tag> is matched with a </tag>. Instead of writing <tag> … </tag> in the tables to indicate a <tag> followed by some intermediate material and then closed with a </tag>, we simply write "<tag>"

 

Coordinate System Parameters Available in all Systems

 

All coordinate systems may include the following optional parameters. These may be used to specify an ellipsoid and other parameters within the coordinate system. See the Custom Ellipsoids and Custom Datums topics for information on ellipsoid and datum specification attributes.

 

Note: Although it is possible to define a coordinate system using <majorAxis>, <eccentricity>, <centerX>, <centerY> and <centerZ> tags, users are strongly advised to define a custom datum and then use the <datum> tag.

 

<majorAxis>

Major axis of the ellipsoid.

<datum>

Datum to be used for this coordinate system.

<eccentricity>

Ellipsoid eccentricity.

<centerX>

X offset to datum center in meters.

<centerY>

Y offset to datum center in meters.

<centerZ>

Z offset to datum center in meters.

<scaleX>

X scale correction.

<scaleY>

Y scale correction.

<falseEasting>

False easting in meters or degrees.

<falseNorthing>

False northing in meters or degrees.

<localOffsetX>

X offset in meters or degrees.

<localOffsetY>

Y offset in meters or degrees.

<localScaleX>

X scale in meters or degrees.

<localScaleY>

Y scale in meters or degrees.

<rotationX>

Datum rotation about the X axis, in units specified by the unit attribute. By default, the rotation is in degrees.

<rotationY>

Datum rotation about the Y axis, in units specified by the unit attribute. By default, the rotation is in degrees.

<rotationZ>

Datum rotation about the Z axis, in units specified by the unit attribute. By default, the rotation is in degrees.

 

The above parameters will be applied in order they occur in the file except that the <datum> tag will always be applied before any other tags related to datum information.

 

Very Important: Note that the false Easting and Northing values are always given in meters or degrees, even in the case of those projections that traditionally use feet. When specifying projection presets one must always convert the desired false Easting and Northing values into meters for use in the XML specification. When the values are viewed in a Manifold coordinate system dialog they are converted to whatever units are active. So, what we see in an XML file is not the same to what we might see in a dialog.

 

Example

 

Some parts of South Carolina use a State Plane coordinate system that uses international feet as a measurement unit instead of survey feet. We could add this as a preset using the following XML:

<xml>

<preset>

  <name>State Plane - South Carolina, NAD 83, Intl Feet</name>

  <category>Custom Presets</category>

  <system>Lambert Conformal Conic</system>

  <datum>North American 1983 (mean for CONUS)</datum>

  <unit>Foot</unit>

  <centerLat>31.83333333333333333333</centerLat>

  <centerLon>-81.0</centerLon>

  <firstStdLat>32.5</firstStdLat>

  <secondStdLat>34.83333333333333333333</secondStdLat>

  <falseEasting>609600.0</falseEasting>

  <falseNorthing>0.0</falseNorthing>

</preset>

</xml>

 

Coordinate System Parameters

 

The following list of valid specifications for coordinate systems allowed in <system> attributes includes all parameters that may be specified for each. An attribute is a pair of tags with the value in between, as in <centerLat>15</centerLat>. Some coordinate systems, such as Latitude / Longitude have no optional parameters that are specific to that coordinate system. In addition to the parameters specified, all coordinate systems allow specification of common parameters.

 

Each coordinate system is listed by its <system></system> name.

 

Coordinate System and Attributes

Description of Attributes (Parameters)

 

 

Latitude / Longitude

No parameters.

 

 

Albers Conical Equal Area

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<firstStdLat>

First standard latitude.

<secondStdLat>

Second standard latitude.

 

 

Azimuthal Equidistant

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Azimuthal Equidistant (Guam)

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Bipolar Oblique Conformal Conic

No parameters.

 

 

Bonne

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Cassini

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Cylindrical Equal Area

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Cylindrical Equidistant

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Donald

No parameters

 

 

Gall

 

<centerLon>

Center longitude.

 

 

Miller Cylindrical

 

<centerLon>

Center longitude.

 

 

Eckert IV

 

<centerLon>

Center longitude.

 

 

Eckert VI

 

<centerLon>

Center longitude.

 

 

Equidistant Conic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<firstStdLat>

First standard latitude.

<secondStdLat>

Second standard latitude.

 

 

Gnomonic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Goode's Homolosine (Interrupted)

No parameters.

 

 

Guyou

 

<centerLon>

Center longitude.

 

 

Hammer

 

<centerLon>

Center longitude.

 

 

Krovak Oblique Conformal Conic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<centerLineAzimuth>

Azimuth of the center line.

<pseudoStdLat>

Pseudostandard latitude.

 

 

Lambert Azimuthal Equal Area

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Lambert Conformal Conic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<firstStdLat>

First standard latitude.

<secondStdLat>

Second standard latitude.

 

 

Lambert Conformal Conic (Single Parallel)

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Mercator

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Modified Polyconic

 

<centerLon>

Center longitude.

<firstStdLat>

First standard latitude.

<secondStdLat>

Second standard latitude.

<trueScaleLon>

True scale longitude.

 

 

Modified Stereographic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Modified Transverse Mercator

(Only used for Alaska with predefined parameters)

 

 

Mollweide

 

<centerLon>

Center longitude.

 

 

Mollweide Interrupted

No parameters.

 

 

New Zealand

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Oblated Equal Area

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<ovalRotationAngle>

Oval rotation angle.

<ovalShapeM>

Oval shape M.

<ovalShapeN>

Oval shape N.

 

 

Oblique Mercator (A)

 

<centerLat>

Center latitude.

<firstLat>

Latitude of the first reference location.

<firstLon>

Longitude of the first reference location.

<secondLat>

Latitude of the second reference location.

<secondLon>

Longitude of the second reference location.

 

 

Oblique Mercator (A, centered)

 

<centerLat>

Center latitude.

<firstLat>

Latitude of the first reference location.

<firstLon>

Longitude of the first reference location.

<secondLat>

Latitude of the second reference location.

<secondLon>

Longitude of the second reference location.

 

 

Oblique Mercator (B)

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<centerLineAzimuth>

Azimuth of the center line.

<rectifiedGridAngle>

Rectified grid angle.

 

 

Oblique Mercator (B, centered)

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<centerLineAzimuth>

Azimuth of the center line.

<rectifiedGridAngle>

Rectified grid angle.

 

 

Orthographic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Peirce

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Polyconic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Robinson

 

<centerLon>

Center longitude.

 

 

Sinusoidal

 

<centerLon>

Center longitude.

 

 

Space Oblique Mercator

 

<ascendingNodeLon>

Longitude of the ascending node.

<completedOrbits>

Number of fully completed orbits.

<orbitInclinationAngle>

Orbit inclination angle.

<rotationToAscendingNode>

Earth rotation to the ascending node.

<satelliteRevolutionTime>

Satellite revolution time.

 

 

Space Oblique Mercator for Landsat

<orbitNumber>

LANDSAT ID for the orbit.

<orbitPathNumber>

LANDSAT ID for the orbit path.

 

 

Stereographic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Double Stereographic

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Polar Stereographic

 

<centerLon>

Center longitude.

<trueScaleLat>

True scale latitude.

 

 

Tilted Perspective

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<centerHeight>

Center height in meters.

<tiltAngle>

Tilt angle.

<tiltAzimuth>

Tilt azimuth.

 

 

Transverse Mercator

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

 

 

Van der Grinten

 

<centerLon>

Center longitude.

 

 

Van der Grinten IV

 

<centerLon>

Center longitude.

 

 

Vertical Perspective

 

<centerLat>

Center latitude.

<centerLon>

Center longitude.

<centerHeight>

Center height in meters.

 

 

Wagner IV

 

<centerLon>

Center longitude.

 

 

Wagner VII

 

<centerLon>

Center longitude.

 

 

Winkel Tripel

 

<stdLat>

Standard latitude

 

Tech Tip

 

Manifold cannot use any customizations if the .xml files do not contain XML that is exactly correct. A useful test before launching Manifold is to open any newly created or modified .xml file in Internet Explorer. Internet Explorer will show a correct .xml file in a simple text format. If Internet Explorer cannot parse the .xml file, Manifold won't be able to either.

 

Caution

 

Defining custom presets for coordinate systems is an expert-level task that requires expertise in details of coordinate systems and projections. Correct choice of and use of parameters requires extensive knowledge of projections. Providing an incorrect specification or inappropriate parameters can provide in erroneous system function. This capability is include within Manifold for the use of experts. It is not supported by any Manifold technical support product.

 

See Also

 

The Earth as an Ellipsoid

Projections