Equirectangular Projection - Revision history

KSiimson: /* Scaling */

2008-07-08T18:07:56Z

‎Scaling

KSiimson: /* Scaling */

2008-07-08T18:06:47Z

‎Scaling

Erik Krause: Prepared for new glossary template

2007-11-17T22:24:02Z

Prepared for new glossary template

Bruno: link to future sharpening page

2007-01-18T22:04:55Z

link to future sharpening page

Bruno: note problems tone-mapping equirectangular

2006-08-16T18:50:34Z

note problems tone-mapping equirectangular

Bruno: typo

2006-07-28T14:22:23Z

typo

Bruno: noted some equirectangular gotchas

2006-07-28T14:00:22Z

noted some equirectangular gotchas

Erik Krause: °

2006-07-28T12:24:20Z

WikiSysop: 18 revision(s)

2006-07-13T20:28:00Z

18 revision(s)

WikiSysop: 1 revision(s)

2006-07-13T19:56:39Z

1 revision(s)

@@ Line 41: / Line 41: @@
 Equirectangular images have a very large amount of data redundancy near the
 poles because they are stretched in the 'latitude' direction.  When downsizing
-an image in an editor such as [[Photoshop]] or the [[Gimp]], the effective
+an image in an editor such as [[Photoshop]] or [[Gimp|the Gimp]], the effective
 resolution of the image is decreased as expected ''except near the poles''.

@@ Line 41: / Line 41: @@
 Equirectangular images have a very large amount of data redundancy near the
 poles because they are stretched in the 'latitude' direction.  When downsizing
-an image in an editor such as [[Photoshop]] or the [[gimp]], the effective
+an image in an editor such as [[Photoshop]] or the [[Gimp]], the effective
 resolution of the image is decreased as expected ''except near the poles''.

← Older revision		Revision as of 22:24, 17 November 2007
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		+	{{Glossary\|A projection capable of mapping the entire sphere to a rectangle with 2:1 aspect ratio.}}
	[[image:big_ben_equirectangular.jpg\|right\|Equirectangular Projection, with permission from Ben Kreunen]]		[[image:big_ben_equirectangular.jpg\|right\|Equirectangular Projection, with permission from Ben Kreunen]]

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 [[Panorama Viewers]].  The solution is to always switch to a less distorted
 projection such as [[Cubic Projection]] before scaling, blurring or
-sharpening a panorama - Switching back later if necessary
+[[sharpening]] a panorama - Switching back later if necessary
 [[Category:Glossary]]

@@ Line 29: / Line 29: @@
 zenith or nadir, you may need to stitch the entire scene in a different
 orientation to get good results.
 === Scaling ===

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 [[image:big_ben_equirectangular.jpg|right|Equirectangular Projection, with permission from Ben Kreunen]]
 This is a type of [[Projections|projection]] for mapping a portion of the surface of a sphere to a flat image.  It is also called the "non-projection", or ''plate carre'', since the horizontal coordinate is simply longitude, and the vertical coordinate is simply latitude, with no transformation or scaling applied.  The equirectangular projection was used in map creation since it was invented around 100 A.D. by Marinus of Tyre.  See [http://mathworld.wolfram.com/EquirectangularProjection.html Mathworld's page] for more detailed information on the mathematics of this projection.
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 The Equirectangular projection is commonly used as the projection type of the source images for spherical [[Panorama Viewers|panorama viewers]], including [[Panorama_tools|PTViewer]]. The other possibility is the [[Cubic Projection]].
 [[Category:Glossary]]

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 In an equirectangular panoramic image all verticals remain vertical, and the horizon becomes a straight line across the middle of the image. Coordinates in the image relate linearly to pan and tilt angles in the real world. The poles ([[Zenith]], [[Nadir]]) are located at the top and bottom edge and are stretched to the entire width of the image.  Areas near the poles get stretched horizontally.
-The Equirectangular projection is the default output format of a rotating (scanning) panorama camera equipped with a fisheye lens -- 180� fisheye giving a full sphere at 360� rotation. Scanning cameras sometimes cover more than one 360� turn but software often assumes that equirectangular images cover 360� horizontally and 180� vertically, i.e. make sure that your equirectangular image has a proper [[Aspect_Ratio|aspect ratio]] of 2:1. Look at the pixel values -- a file with 1650 x 824 pixels lacks one pixel at the short side thus confusing some applications.
+The Equirectangular projection is the default output format of a rotating (scanning) panorama camera equipped with a fisheye lens -- 180° fisheye giving a full sphere at 360° rotation. Scanning cameras sometimes cover more than one 360° turn but software often assumes that equirectangular images cover 360° horizontally and 180° vertically, i.e. make sure that your equirectangular image has a proper [[Aspect_Ratio|aspect ratio]] of 2:1. Look at the pixel values -- a file with 1650 x 824 pixels lacks one pixel at the short side thus confusing some applications.
 The Equirectangular projection is commonly used as the projection type of the source images for spherical [[Panorama Viewers|panorama viewers]], including [[Panorama_tools|PTViewer]]. The other possibility is the [[Cubic Projection]].
 [[Category:Glossary]]

← Older revision	Revision as of 20:28, 13 July 2006
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