Copyright 1980 IEEE, Reprinted, with permission, from IEEE Transactions on
      Geoscience and Remote Sensing, GE-18, Num 1, 36-38, 1980.

This material is posted here with permission of the IEEE. Such permission of
the IEEE does not in any way imply IEEE endorsement of any of PDS's products
or services. Internal or personal use of this material is permitted.
However, permission to reprint/republish this material for advertising or
promotional purposes or for creating new collective works for resale or
resdistribution must be obtained from the IEEE by sending a blank email
message to info.pub.permission@ieee.org.
 
By choosing to view this document, you agree to all provisions of the
copyright laws protecting it.