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Assuming longitude is E-handed (EPN-TAP convention, and IAU convention in planetocentric frames):

• Standard setup for planetary maps in TOPCAT SkyPlot:

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Healpix generation from a table in TOPCAT

Healpix is a tesselation system on the sphere, depending on a resolution/scale parameter.
The point is to easily get a combined map from sparse data; the result is also scalable in resolution, at least degradation is performed correctly by combining healpix cells.

In TOPCAT, load a table containing a list of observations located in lon/lat
(working example is a large table of VIRTIS/Rosetta observations of 67P)

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• Back to the Form panel, select parameter to plot as Weight (will be weighted by density), select combine mode, and adjust scale. Healpix generation is performed on the fly, so all scales are OK.

• Possibly adapt color scale in the Aux Axis tab (left menu)

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• In Skyplot / Style panel, use Degrade and Combine mode to reduce resolution on the fly .(super-resolution can no longer be achieved)

Mars HiPS generation in Aladin

HiPS (Hierarchical progressive survey) are associations of healpix maps at different scales. They provide multiresolution scaling on the fly in Aladin.


• In Aladin, load file Mars_MGS_colorhillshade_mola_1024.jpg

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• The hpx image should be saved on disk automatically


MOC use case in Aladin

MOC (Multi-Order Coverages) are footprints defined in terms of healpix cells list mixing various resolutions. They provide immediate location information e.g. about intersections.


- Load Mars MOLA hpx in Aladin

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