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(Warning: this tutorial uses undocumented Hipsgen parameter)
P.Fernique - 2nd of July 2019 -

1) You need a cartesian map in JPEG, PNG format covering the whole body (or sky)
   Rq: if you have it in TIFF see 4
2) You need to generate a World Coordinate System (WCS) solution for you map.
   It is a small ASCII file with the same name and the .hhh extension containing the
   WCS solution of your image:
ex: Cartesian hhh file content for a 2880x1440 map
NAXIS1  = 2880          // ImageWidth
NAXIS2  = 1440          // ImageHeight
CRPIX1  = 1440          // ImageWidth/2          => central pixel x coord
CRPIX2  = 720           // ImageHeight/2         => central pixel y coord
CRVAL1  = -0.0625       // -(360/imageWidth)/2   => longitude of the central pixel
CRVAL2  = -0.0625       // -(180/imageHeight)/2  => latitude of the central pixel
CD1_1   = 0.125         //  360/imageWidth       => pixel resolution
CD1_2   = 0
CD2_1   = 0
CD2_2   = 0.125         //  180/ImageHeight       => pixel resolution

   a) you can do that manually via any ASCII editor
   b) Or programmatically thanks to Hipsgen.jar itself. In this last case,
   just launch this kind of command:  
   java -jar Hipsgen.jar -hhh="path/FileName widthxheight"
   ex: java -jar Hipsgen.jar -hhh="path/Titan.jpg 2880x1440"
   Note: if your longitude origin is not localized at the central pixel line of your map, you can add its x coordinate as a third parameter (ex: java -jar Hipsgen.jar -hhh "path/Titan.jpg 2880x1440 0")  
3) After that you can generate your HiPS by this kind of command
    java -jar Hipsgen.jar in=path out=MyHips id="YourAUTH/P/Titan" color=jpg
Rq: you can also do steps 2 and 3 in one unique Hipsgen command
java -jar Hipsgen.jar -hhh="path/Titan.jpg 2880x1440" in=path out=MyHips id="YourAUTH/P/Titan" color=jpg
4) If your original image is really big, and/or in TIFF format, it is preferable to convert and to split it in a collection of small JPEG subimages before launching Hipsgen process. ImageMagick toolkit (free on Linux) does that magically thanks to this command:
convert srcImage.tif -crop widthCellxheightCell +repage TargetDir/GenericName.jpg
It is better to have subimages with the same size (one divisor factor of the source image)
ex :
convert Lunar_LRO_LROC-WAC_Mosaic_global_100m_June2013.tif -crop 10112x10112 +repage SplitImg/Moon.jpg

And thus, launch Hipsgen.jar with -hhh parameter with one additional parameter as size of subimages
java -jar Hipsgen.jar -hhh="SplitImg/Moon.jpg 92160x40448 10112x10112"

or in one Hipsgen command like this:
java -jar Hipsgen.jar hhh="SplitImg/Moon.jpg 92160x40448 10112x10112" in="SplitImg" creator_did="XXX/P/Moon/LROC-WA-GLD100-118m" -f color=jpg

5) in order to get the longitude direction right in Aladin, you may have to edit the generated index.html and change the following line :

aladin.setImageSurvey(aladin.createImageSurvey('2019-0712-1456', '2019-0712-1456', hipsDir hipsDir, 'equatorial', 3, {imgFormat: 'png'}));
aladin.setImageSurvey(aladin.createImageSurvey('2019-0712-1456', '2019-0712-1456',
 hipsDir hipsDir, 'equatorial', 3, {imgFormat: 'png' ,longitudeReversed: true}));

You can alternatively set hips_frame to planet name (will change coord.sys). In Aladin Desktop you can also set properties to .longitude = ascending

MOC use case in Aladin

(updated May 2019)

MOC (Multi-Order Coverages) are footprints defined in terms of a healpix cells list mixing various resolutions. They provide immediate location information e.g. about intersections, and can accommodate footprints of arbitrary complexity (hollowed, non-connex, etc…). There is no explicit contour associated, so the usage is different from the s_region parameter.

  •  Should also retain info about original file coverages, for callback purpose - TBC

- Load previous Mars MOLA HiPS in Aladin

- Select two large craters in Mars Craters service from VESPA client

- send as s_region from VESPA client (to Aladin) — (s_region was then provided in this service with W longitudes, so this projected correctly)

- select them in Aladin with pointer

- Generate common MOC for these 2 craters (Coverage > Generate a MOC based on… > selected drawing objects)

- You can save it from File > Export Planes (save preferably as fits for reuse)

This is straightforward and very quick.
This is not a direct alternative to s_region however: the result is a list of healpix cells which is much larger than a contour, and can't be included in a table. But we can either have precomputed MOC stored somewhere (for complete datasets? Especially with time direction added), or compute them on the fly when required.

• Next step: test intersections with something else - see example in the next pages