User's Guide to
An Astronaut's View of California
Bill Daley and Fred Brumbaugh
Hernandez Engineering, Earth Sciences and Image Analysis,
NASA Johnson Space Center
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These images presented in our database are very easy to use and
understand. Most of the images are natural color photographs. Since
these photos are in natural color many of the features are easy to
identify. For example, water appears as different shades of blue,
unless sediments are present (in which case the water can appear as a
variety of colors, including browns, tans, or yellows). Vegetation can
be seen as dark blues, shades of green, or even browns; while sparsely
vegetated deserts are generally shades of browns or yellows, depending
upon parent soils and weathering conditions of the surrounding rocks.
In addition to the natural color photographs, several color infrared
photographs have also been included in the database. Remember that
color infrared photography generally shows green vegetation as shades
of red and water surfaces are generally dark, usually black or deep
blue.
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Orientation of California Images
The California images are orientated in the look direction that the
astronaut's took the photographs. The true North is not always at the
top of the frame. Please consult a map and identify approximately three
features or landmarks to determine the North and South locations.
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Scale of California Images
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Each image may be a different scale. Astronauts use different lens
combinations that result in images that have a variety of look angles
and scales. Spacecraft altitude, which varies from one mission to the
next, is also a factor in determining the scale of a photograph. To
determine the photo's scale, use a map of known scale and identify two
features on both the map and photograph. Using this information and
known map scale, you can compute the scale of your photograph. This
scaling technique is only true for near-vertical photography. Remember
that when viewing oblique photography the scale will continue to change
as a function of the ground distance from the camera.
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