## DESCRIPTION

The Projector module is designed to transform data with geographic coordinates into one of several standard map projections.## INPUTS

**Port:** Map

**Type:** Pyramid

**Optional:** This port is optional

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Pyramid 1

**Type:** Pyramid

**Optional:** This port is optional

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Pyramid 2

**Type:** Pyramid

**Optional:** This port is optional

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Pyramid 3

**Type:** Pyramid

**Optional:** This port is optional

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Lattice 1

**Type:** Lattice

**Optional:** This port is optional

**Port:** Lattice 2

**Type:** Lattice

**Optional:** This port is optional

## WIDGETS

**Port:** Projection

**Type:** Option Menu

**Menu Item:** Cartesian

**Menu Item:** Mercator Cyl

**Menu Item:** Lambert Cyl

**Menu Item:** Gnomonic Azi

**Menu Item:** Stereographic Azi

**Menu Item:** Orthographic Azi

**Menu Item:** Postel Azi

**Menu Item:** Lambert Azi

**Menu Item:** Lambert Con

**Menu Item:** Albers Con

**Menu Item:** Cassini-Soldner

**Menu Item:** Bonne Con

**Menu Item:** Werner

**Menu Item:** Sanson-Flamsteed

**Menu Item:** Globe

The Projection option menu is used to select the particular map projection to be applied. These projections make use of some or all of the Base Longitude, Base Latitude, 1st. Standard Parallel, and 2nd. Standard Parallel dials. The implemented projections are listed below along with a brief explanation of their properties, utility, and parameters. Projections are classified according to their properties. A projection may be conformal, preserving the shapes of structures while distorting their scale, equivalent, preserving the area of structures, or equidistant, preserving distances in one or more directions. A Projection may also be azimuthal, based on some projection of the globe onto a plane tangent at one point, cylindrical, based on the projection of the globe onto a cylinder tangent (usually) at the equator, or conic, based on the projection of the globe onto a cone which intersects the globe at one or two standard parallels.

Available Projections

Cartesian Parameters: Base Long., Base Lat. Properties: None Longitude and Latitude map directly to x and y except that they are scaled to make equatorial and meridian distances correct in proportion to altitudes. This projection is seldom seen on maps, is considered cylindrical, and preserves no particular quality. This projection has no parameters.

Mercator Cylindrical Parameters: Base Long., Base Lat. Properties: Conformal This is the standard Mercator projection. It is a cylindrical conformal projection. The Base Longitude parameter sets the center of the map but has no noticeable effect. This projection goes to infinity as latitude approaches the poles, therefore such data should be cropped.

Lambert Cylindrical Parameters: Base Long., Base Lat. Properties: Equivalent This is an equivalent projection. The Base Longitude parameter sets the center of the map but has no noticeable effect. Structures at the poles become flat in this projection.

Gnomonic Azimuthal Parameters: Base Long., Base Lat. Properties: None Projection is made from a perspective point at the center of the globe onto a plane which is tangent to the globe at (Base Longitude, Base Latitude). As with all azimuthal projections, great circles on the globe passing through the tangent point appear as straight lines radiating from it. This is the simplest azimuthal projection but has no special properties. Care should be taken in cropping data to avoid points which appear on the other side of the world from the tangent point, as this will produce undesirable results.

Stereographic Azimuthal Parameters: Base Long., Base Lat. Properties: Conformal Projection is made as above but from a perspective point on the surface of the globe exactly opposite the tangent point. This projection has the added property of being conformal. As above, all data points should be on the same side of the globe as the tangent point.

Orthonormal Azimuthal Parameters: Base Long., Base Lat. Properties: None Projection is made onto a plane as above from a point at infinity. This projection gives the effect of looking a a globe, but the projection is flat. Data points should be on the same side of the globe as the tangent point. To achieve the effect of looking at a globe, the actual Globe projection is recommended.

Postel Azimuthal Parameters: Base Long., Base Lat. Properties: Equidistant Also known as the azimuthal equidistant projection, this is useful for determining distances from a given origin. The distance from the point (Base Longitude, Base Latitude) to any other point on the map will be equal to that actual distance on the surface of the earth.

Lambert Azimuthal Parameters: Base Long., Base Lat. Properties: Equivalent Lambert's azimuthal equivalent projection. There is no distortion of area and the minimal distortion of shape occurs at the base point.

Lambert Conical Parameters: Base Long., Base Lat., 1st. St. Par., 2nd. St. Par. Properties: Conformal Lambert's conformal conical projection. Minimal distortion of area occurs at in the region between the 1st. Standard Parallel and the 2nd. Standard Parallel. The Base Longitude parameter sets the center of the map but has no noticeable effect.

Albers Conical Parameters: Base Long., Base Lat., 1st. St. Par., 2nd. St. Par. Properties: Equivalent Albers' equivalent projection. Minimal distortion of shape occurs at in the region between the 1st. Standard Parallel and the 2nd. Standard Parallel. The Base Longitude parameter sets the center of the map but has no noticeable effect. An interesting property of this projection is that the pole maps to a section of a circle, effectively truncating the cone.

Cassini-Soldner Parameters: Base Long., Base Lat. Properties: Equidistant This is a cylindrical equidistant projection in which the cylinder lies at a right angle to the earth's axis. It is useful only for areas which extend mainly in the north-south direction. The Base Longitude parameter sets the meridian of contact for the cylinder and horizontal distances from this central meridian are correct. Distortion occurs mostly in the vertical direction and increases with distance from the central meridian.

Bonne Conical Parameters: Base Long., Base Lat. Properties: Equivalent Actually Bonne's pseudo conical equivalent projection. Scale is preserved only on the central meridian, set by the Base Longitude parameter, and along the parallels. Minimal shape distortion is achieved along the Base Latitude. This projection produces highly curved maps which are useful mainly for projections of an entire hemisphere.

Werner Parameters: Base Long., Base Lat. Properties: Equivalent The Werner projection produces an equivalent heart shaped map, centered on the Base Longitude and is actually a form of Bonne's projection. The Base Latitude determines only which hemisphere is at the top of the heart. Useful for viewing the entire globe.

Sanson-Flamsteed Parameters: Base Long., Base Lat. Properties: Equivalent The Sanson-Flamsteed projection produces an equivalent symmetric map, centered on the Base Longitude and the equator. This is also a form of Bonne's projection and is useful for viewing the entire globe.

Globe Parameters: None Properties: No distortion This produces an actual three-dimensional globe with radius Globe Radius. If necessary (as when displaying the entire globe) the module SimpleSphere may be used to place a sphere inside the globe in order to avoid seeing through it.

**Port:** Globe Radius

**Type:** Text

The Globe Radius parameter is required and should contain the radius of the earth in the same units as the altitudes in the data set. This parameter is used in all map projections to provide proper scaling of longitude and latitude.

**Port:** Base Long.

**Type:** Dial

The Base Longitude parameters indicate the point on the globe which will be the center of the map. This is important because this is usually the area with the least distortion. The Base Longitude parameter may take on any value, but should be in the same range as the data.

**Port:** Base Lat.

**Type:** Dial

The Base Latitude parameters indicate the point on the globe which will be the center of the map. This is important because this is usually the area with the least distortion. The Base Latitude parameter is limited to the range [-90,90].

**Port:** 1st. St. Par.

**Type:** Dial

The 1st. Standard Parallel is used by the conic projections to indicate the intersection of the cone with the earth. These parameters should be chosen to border the area of interest and the 1st. should be greater than or equal to the 2nd. If they are equal, the cone will only touch the earth and not penetrate it.

**Port:** 2nd. St. Par.

**Type:** Dial

The 2nd. Standard Parallel is used by the conic projections to indicate the intersection of the cone with the earth. These parameters should be chosen to border the area of interest and the 1st. should be greater than or equal to the 2nd. If they are equal, the cone will only touch the earth and not penetrate it.

**Port:** Map z

**Type:** Text

The Map z parameter sets the amount the 1st. pyramid (the Map) will be shifted in the positive z direction. This allows the map (which is usually at z=0) to be placed, for example, above air masses or below seismic data.

## OUTPUTS

**Port:** Map

**Type:** Pyramid

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

Output Pyramid of the globe

**Port:** Pyramid 1

**Type:** Pyramid

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Pyramid 2

**Type:** Pyramid

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Pyramid 3

**Type:** Pyramid

**Constraints:** n-layer.

optional-baseLat.

n-D compression.

n-compression type.

**Port:** Lattice 1

**Type:** Lattice

**Port:** Lattice 2

**Type:** Lattice

## PROBLEMS

## SEE ALSO

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