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cassini 'world' projection appears incomplete

January 26 2011 | 0 comments
Categories: ArcGIS Methods, Map Data

hi,

in perusing the various projections in the 'world' (spheroid) folder, i came across a projection, cassini (world) that does not show the entire world.

if you go to this wwweb site, you can see the entire world using the
cassini projection:

http://www.progonos.com/furuti/MapProj/Dither/ProjCyl/projCyl.html

the difference between the esri implementation of cassini world projection
and the one shown on the progonos page is that the progonos page map uses two central meridians. esri's implementation uses one central meridian.

can that situation be fixed so the esri implementation of the cassini projection shows the entire world?

perhaps there's a work-around that i'm not aware of.

thanks,
ryan rudnicki

Mapping Center Answer:

We do support that type of Cassini projection, but only in the spherical form. The geographic coordinate system (GCS) must be based upon a sphere. In this case, use the definition from the World (Sphere-based) folder as a starting point.

The projection definition in the World folder uses WGS84 for the GCS, thus it will use the ellipsoidal version which is designed for large scale maps, not for displaying the world. Cassini, in its ellipsoidal form, is more like transverse Mercator. Attached is a map using the sphere-based projection, with the central meridian set to -90.

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