USGS Frequently Asked Questions

FAQ's about Remote Sensing

What do the different colors in a CIR aerial photograph represent?

What is CIR, B/W, BIR, and natural color?

What is meant by focal length?

What is meant by resolution of an aerial photograph?

What film type is best for me?

What is the difference between a Band and a Channel?

Does red in ASTER images always represent vegetation?

Why measure the magnetic field at the Earth’s surface? Wouldn’t satellites be better suited for space-weather studies?

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?

Why are there so few international Landsat scenes available from USGS?

Could you give a brief description of ASTER and its sensor systems?

Why are some of the Landsat TM browse images so blocky?

Why do some Landsat 7 browse images appear to be split midway through a scene?

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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