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The site http://spatialreference.org gives 'Projected Bounds' and 'WGS84 Bounds' for each Coordinate System. What does these 'bounds' mean? e.g. for ETRS89 / UTM zone 32 N this is given:enter image description here

I know what the difference between 'WGS84' and 'Projected' means. I want to know why there are 'bounds'.

In epgs.org there are no such bounds. For 'ETRS89 / UTM zone 32 N' epsg.org says: enter image description here So epsg.org includes Germany (which is valid) while the bounds of spatialreference.org did not include Germany.

(I want to understand what the 'bounds' mean because AutoCAD Map 3D seams do use these bound when consuming a WGS service.)

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The area of use (2126) changed its extents in EPSG CR 2005.140 as part of publishing the polygons. That was only finalized in 2012, so spatialreference.org is just out of date. –  mkennedy Apr 15 '13 at 17:24
    
@mkennedy thanks for this information. can you give me a link to the source of this information? (I can not find information about CR 2005.140 that states that the area of 2126 has changed) –  Jens Apr 16 '13 at 11:15
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I'm sorry! It was 2011.082 that amended the description and bounding box. I found this by looking up the area of use for the CRS and seeing which change requests were listed for it, then reviewing them. This CR was closed on Jan 5, 2012. –  mkennedy Apr 16 '13 at 11:39
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The bounds are the area that the projection is "well defined" for. The most well known example of a poorly behaved projection is spherical mercator as you move towards the poles (>85 degrees). The projected bounds is this area in the units and projection of the CRS you are interested in while WGS84 bounds are those corners (un)projected in to WGS84.

So I would guess (and with out reading the manual or the code its hard to tell) that the AutoCad developers decided to avoid the risk of mathematical instability or unacceptable errors creeping in and limited you to the safe bounds.

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Thanks for the information. UTM 32 is the official CRS for Germany. The N/S range of Germany is 55 to 47 degree. So why is Germany not included in the "well defined" range? Who defines the "bounds" in spatialreference.org? Is the a (official) source who defines the bounds? –  Jens Apr 15 '13 at 8:28
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I think that you need epsg.org/polygons/main.html but I can't be sure –  iant Apr 15 '13 at 8:42
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Although the statements in this reply are correct, they do not appear to explain the example provided in the question. The "bounds" and the "projected bounds" describe a region in southern Norway; they are much more restrictive than the domain in which UTM 32N is defined. –  whuber Apr 15 '13 at 12:07
    
@iant I investigated epsg.org/polygons/main.html. I now understand what the purpose and the source of the ‘bounds’ are. Thanks very much. –  Jens Apr 15 '13 at 12:37
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@whuber: the ‘CRS area of use’ and the ‘polygons’ in epsg.org for UTM 31, UTM 32 and UTM 33 are quite useful. The bounds for UTM 31 and UTM 33 at spatialreference.org are quite useful too and are the same as in epsp.org. But the bounds for UTM 32 are at spatialreference.org (and Autodesk) are not useful. I suspect an error at spatialreference.org (and Autodesk)!? –  Jens Apr 15 '13 at 12:38
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