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Google sky
 
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David Larson



Joined: 25 Sep 2004
Posts: 11
Affiliation: Johns Hopkins University

PostPosted: August 27 2007  Reply with quote

The "Sky" addition to google earth looks like it would be a good teaching tool. http://earth.google.com/
There's already some CMB data available from: http://earth.google.com/gallery/index.html although it looks like the web site serving the microwave data is down for the moment.

I'm not sure who put that information together. If anyone knows, I'd like to talk to them about how they did it. (I've only played with the formats for displaying data a little bit, so far.) This looks like a good opportunity for public outreach, so I'd like to have more WMAP data (and also data from higher-resolution, partial sky CMB experiments) available, too.
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Joe Zuntz



Joined: 22 Oct 2004
Posts: 9
Affiliation: UCL

PostPosted: August 31 2007  Reply with quote

It's very easy to put your own full sky maps on manually.

Use the Healpix IDL routine cartview with the reso_arcmin, pxsize and pysize set large, so that you get the full sky in the cartesian projection. The annoying bit is that you then have to cut the resulting image to remove the extraneous stuff outside the map.

Then in Google Earth go to Add>Image Overlay and load the map image. Set the locations to 90 N, 90S, 180E and 180W.

Doing partial sky maps would need a little bit more fiddling with locations and orientations to look right.
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David Larson



Joined: 25 Sep 2004
Posts: 11
Affiliation: Johns Hopkins University

PostPosted: August 31 2007  Reply with quote

Thanks. I ended up writing what is probably the equivalent of your recommendation. See the (only minimally documented) idl scripts in http://www.pha.jhu.edu/~dlarson/google_sky/
These don't end up with extra image data to crop.

I still haven't sat down to figure out how to do multi-resolution maps, so that a lot of image data can be made available, but only the part that is immediately needed for viewing gets downloaded. I'll get to that eventually...
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Eric Hivon



Joined: 25 Sep 2004
Posts: 7
Affiliation: IAP

PostPosted: September 03 2007  Reply with quote

Quote:
Use the Healpix IDL routine cartview with the reso_arcmin, pxsize and pysize set large, so that you get the full sky in the cartesian projection. The annoying bit is that you then have to cut the resulting image to remove the extraneous stuff outside the map.


There is no need for the annoying part: the CROP keyword in cartview will just crop anything out of the main image (ie: title, color bar, ...) in the GIF or PNG file you create (even if the IDL window remains uncropped). When using
Code:
cartview,/crop,reso=,pxsize=,pysize=
for full sky Google Earth you only have to make sure that
reso * pxsize = 60 * 360
reso * pysize = 60 * 180

So, for instance:
Code:
 mapfile = ??? ; input data file
reso = 30 ; final resolution in arcmin
cartview, mapfile, reso=reso, pxsize=360*60./reso, pysize=180*60./reso,png='GEfile.png', /crop

will create a full sky png file (GEfile.png) of your map ready to be used by Google Earth, with the boundaries (90,−90,180,−180), here with a resolution of 30 arcmin.
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