Lenses

HyperLens® implements the "Magic Lenses" first described by Xerox PARC (who also invented the user interface now familiar on most computers under names such as "Windows"). As far as we know, this is the first implementation of lenses outside of theoretical computer science.

Lenses in HyperLens® serve the purpose of Layers in traditional GIS, CAD, or image processing software. Indeed, if you expand every lens to cover an entire scene, they are identical to GIS layers. However, these lenses are an altogether more flexible and powerful device than traditional layers.

As the name suggests, lenses display only a window on a selected area under the control of the user. They can not only be turned on and off, but may be moved, resized, re-ordered, or even made partially or wholly transparent, bringing a new level of interactivity to the viewing experience.

Lenses can show any view on an image: a lens may be a filter, may contain another image or description file, or may simply offer a function. It can have additional controls, such as a control panel or a JavaScript link to a web browser.

The HyperDAAC uses the following lens types:

• Colourmapped Bitmap Image Lenses to display AVHRR bands 1-9
• Bitmap Image Lenses with interactive user-defined colourmap to display Land Classification and Date Index bands.
• Filter Lenses to display the NDVI composite as greyscale
• Pseudo-lenses to define queries (scenes).

Every lens is identified by its colour, and has:

• An on/off button - lit when turned on - in the control panel left of the display.
• A wire frame outline, in the lenses own colour.
• Control tabs: top left (to drag the lens) and bottom right (to resize it).
• Other attributes and possibly controls defined by the lens itself.

The image shows a fragment from a scene with two lenses. The USGS band is uppermost: this will change if the user selects the NDVI band by moving or resizing it, or simply toggling it off/on. The user has highlighted certain bands in the USGS lens; other bands are unselected and their pixels are transparent.

See Also

• Overview
• Scenes
• HyperDAAC