KML Now! Development Wiki
KML Now! has been discontinued, but this wiki remains to provide insight to developers interested in learning from our work.
If you're looking for the KML Now! front page, go here: KML Now!
Instructions for how to use KML Now are available on the service front page
How it Works
The internal workings of KML Now are explained in this SPIE Newsroom article
and in this poster
presented at the January 2009 meeting of the American Astronomical Society.
Most Recent Developments
We are currently using command line tool VO-CLI to communicate with the SIA services. Unfortuantely, working with VO-CLI has been problematic, and the source code is difficult to understand. Ron prefers to write his on HTTP code in Python and use SIA service URLs to communicate directly with the image services. Jared has written a simple Python script to convert input coordinates (RA and Dec) to decimal degrees; this will allow Ron to build the HTTP GET URL based on the user's input.
"Features" / limitations / bugs
- Only the first FITS file returned in KML Now's VO query response is converted for Sky import. Other files are ignored. The number of images returned by a response is visible from the (non-public, behind-the-scenes) admin page in the vodata program log. These example queries return multiple image URLs:
- The default query (17:45:40, -29:00:28, 10, Improved Reprocessing of the IRAS Survey: 12) should return 4 images per query
- (03:19:48.1, 41:30:42, 1, NRAO VLBA 2cm Survey) should return 8 images.
- (03:19:48.1, 41:30:42, 1, Chandra X-Ray Observatory Data Archive) returns 100 images.
- Coordinate formatting is strictly enforced. Remember your semicolons!
- If you enter RA as "12 00 00" instead of "12:00:00", the invocation of vodata fails. The user sees an error message in Google Sky: "metadata from VO query is incomplete". This message is not correct, since the query was never sent.
- The service should allow spaces or semicolons. Currently spaces cause a problem because vodata interprets the space as a seperator between command line arguments. A single floating point number is allowed, and this should be maintained.
- Only FITS images with 2 non-degenerate axes are supported. Our conversion routine does not yet support multiple channel or polarization planes.
- It's not yet clear what the best solution is for handling this type of data. Some possibilities include:
- Split out every plane and process separately;
- Use only one plane, perhaps the first plane or the middle plane;
- Sum all the planes together.
- All of these solutions require some type of software to do the FITS file manipulation. I think Mike Fitzpatrick (or Doug Tody?) mentioned that some software included with IRAF can split out FITS image planes.
- Compressed (i.e. G-zipped) FITS images are not supported.
- This service returns g-zipped files: "CADC/CFHT Image Search". The easy solution would be to remove this service from the list.
- The following query returns a FITS file that does not contain a ".fits" extension. No error message is returned through KML; only the icon in the "Places" side bar indicates that something may have gone wrong. KML Now reports through the admin interface that "VO image file does not appear to be FITS".
- QUERY: ra = 17:45:40, dec = -29:00:28, radius = 0.1, SIA = 2MASS All-Sky Atlas Image Service
- Possible solution to FITS format authentication:
- An error message should be sent through KML when a file is flagged as not being FITS format.
- The Unix utility 'file' correctly identifies this file as FITS image data. Perhaps 'file' could be used to verify that downloaded files are indeed FITS files.
Suggested Improvements -- down the road
- Allow KML Now queries from within Google Sky. If this can be accomplished, an external Web page interface will not be necessary. The user can send queries and receive KML documents all from within Google Sky.
Set ALLOWTOPICCHANGE = JaredCrossley