Remote-sensed satellite data can be used to answer questions about urban development, resource management and environmental monitoring. Satellite images show change in land cover by color variations, where gray = no change, red = seasonal loss, blue = seasonal increase, darker = land cover loss, and lighter = land cover increase ... . New suburbs where houses replace grassland appear dark red, and while areas of native forest regrowth in abandoned pastures appear light blue. These images show overall and intermediate levels of information, but the color of a single pixel, or highly variegated region, may be difficult to perceive because high spatial frequencies in hue can exceed the resolving capability of the eye ... .
The question is "what is the change in land-cover here?" with answers-large loss, loss, no change, increase, and large increase. The design was seeded from examples about casting a fishing line, filling an opaque water bottle, and shaving with an electric razor. These examples have an ordered change in some aspect of the sound that enables comparisons of more or less-the duration of "whizzing" of the cast, the pitch change of the water bottle and the "buzziness" of the razor.
The examples also have categorical distinctions. A good cast sounds "sweet" and a bad cast sounds "clutzy". The full water bottle is distinctly higher and brighter than the empty one. When shaving one can hear the "hairy" and "smooth" ends of the process as distinctive timbres. These examples were used to design a sound sequence that has two categories, and also allows comparisons of more and less along a scale.
The rule-base suggests distinct timbres to represent distinct categories (loss, no change, and increase) and pitch to enable comparison (i.e. increase vs large increase). Personify,[a sound editing tool], was used to select a brightness interpolation from a bass clarinet at the (large loss) extreme to a bassoon at the other (large increase) extreme. The midpoint (no change) is a dull sound that is not readily identifiable as either timbre. The ordered levels are represented by five ordered pitches, spaced widely to aid identification, from pitch G2 at (large loss) to pitch E4 at (large increase).
The integrated display is a land cover change image in which individual pixels (80x60 meters resolution for Landsat MSS data) can be heard by tapping them with the mouse. The overall and intermediate structure can be seen in color variation. Local queries and point comparisons that are difficult to see may be answered by listening instead.