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USGS Frequently Asked Questions

FAQ's about Remote Sensing

What do the different colors in a CIR aerial photograph represent?
What is meant by focal length?
What is CIR, B/W, BIR, and natural color?
What is meant by resolution of an aerial photograph?
What film type is best for me?
Why measure the magnetic field at the Earth’s surface? Wouldn’t satellites be better suited for space-weather studies?
What is the difference between a Band and a Channel?
Does red in ASTER images always represent vegetation?
Is there an index map for available ASTER images?
What on-line resources are available to learn more about ASTER?
What is Landsat 7?
Why should I take time to preview a satellite image?
How is the cloud cover calculated, and why are some scenes cloudy when the cloud cover is reported to be 0%?
Why do the Landsat 7 (ETM+) browse images look so different from the Landsat 4/5 (TM) images?
Could you give a brief description of ASTER and its sensor systems?
Why are there so few international Landsat scenes available from USGS?
Why do some Landsat 7 browse images appear to be split midway through a scene?
Why are some of the Landsat TM browse images so blocky?
Why is there so much color variation among the Landsat 7 browse images?
What should I do if I have a question pertaining to ASTER Level 1 data that is not addressed in the Customer Support Center?
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