Icosahedral Snyder Equal Area¶
Snyder’s Icosahedral Equal Area map projections on polyhedral globes for the dodecahedron and truncated icosahedron offer relatively low scale and angular distortion. The equations involved are relatively straight-forward, and for certain instructional tools and databases, the projections are useful for world maps. The interruptions remain a disadvantage, as with any low-error projection system applied to the entire globe [Snyder1992].
Classification |
Polyhedral, equal area |
Available forms |
Forward, spherical |
Defined area |
Global |
Alias |
isea |
Domain |
2D |
Input type |
Geodetic coordinates |
Output type |
Projected coordinates |
Parameters¶
Note
All parameters are optional for the projection.
-
+orient
=<string>
¶ Can be set to either
isea
orpole
.
-
+azi
=<value>
¶ Azimuth.
Defaults to 0.0
-
+aperture
=<value>
¶ Defaults to 3.0
-
+resolution
=<value>
¶ Defaults to 4.0
-
+mode
=<string>
¶ Can be either
plane
,di
,dd
orhex
.
-
+lon_0
=<value>
¶ Longitude of projection center.
Defaults to 0.0.
-
+lat_0
=<value>
¶ Latitude of projection center.
Defaults to 0.0.
-
+R
=<value>
¶ Radius of the sphere given in meters. If used in conjunction with
+ellps
+R
takes precedence.
-
+x_0
=<value>
¶ False easting.
Defaults to 0.0.
-
+y_0
=<value>
¶ False northing.
Defaults to 0.0.