Footprints
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The Footprint is a representation of the regions of the sky covered by a catalog.

When the Footprint box is checked, the presentation of the catalog includes a small image (88x44 pixels) of the sky, on which locations covered by the catalog are in a brighter color. A larger image is available from a click on the icon, with possibilities of changing the resolution, the projection, the coordinate system, the color scale, etc... see an example of a footprint illustration for the IRAS catalogues.

The footprints are currently computed from a hierarchical representation of the sky (the Qboxes), and adjacent regions are recursively merged as long as regions are not empty. This representation leads to large uniform areas for deep surveys of large fractions of the sky. Ultimately the very large surveys show a uniform spherical density.

last update 30 Oct 06:09

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