# Info on Johns Hopkins University Ionosphere Data Base

    1. Title: Johns Hopkins University Ionosphere database

    2. Source Information:
       -- Donor: Vince Sigillito (vgs@aplcen.apl.jhu.edu)
       -- Date: 1989
       -- Source: Space Physics Group
                  Applied Physics Laboratory
                  Johns Hopkins University
                  Johns Hopkins Road
                  Laurel, MD 20723

    3. Past Usage:
       -- Sigillito, V. G., Wing, S. P., Hutton, L. V., \& Baker, K. B. (1989).
          Classification of radar returns from the ionosphere using neural
          networks. Johns Hopkins APL Technical Digest, 10, 262-266.

          They investigated using backprop and the perceptron training algorithm
          on this database.  Using the first 200 instances for training, which
          were carefully split almost 50% positive and 50% negative, they found
          that a "linear" perceptron attained 90.7%, a "non-linear" perceptron
          attained 92%, and backprop an average of over 96% accuracy on the
          remaining 150 test instances, consisting of 123 "good" and only 24 "bad"
          instances.  (There was a counting error or some mistake somewhere; there
          are a total of 351 rather than 350 instances in this domain.) Accuracy
          on "good" instances was much higher than for "bad" instances.  Backprop
          was tested with several different numbers of hidden units (in [0,15])
          and incremental results were also reported (corresponding to how well
          the different variants of backprop did after a periodic number of
          epochs).

          David Aha (aha@ics.uci.edu) briefly investigated this database.
          He found that nearest neighbor attains an accuracy of 92.1%, that
          Ross Quinlan's C4 algorithm attains 94.0% (no windowing), and that
          IB3 (Aha \& Kibler, IJCAI-1989) attained 96.7% (parameter settings:
          70% and 80% for acceptance and dropping respectively).

    4. Relevant Information:
       This radar data was collected by a system in Goose Bay, Labrador.  This
       system consists of a phased array of 16 high-frequency antennas with a
       total transmitted power on the order of 6.4 kilowatts.  See the paper
       for more details.  The targets were free electrons in the ionosphere.
       "Good" radar returns are those showing evidence of some type of structure
       in the ionosphere.  "Bad" returns are those that do not; their signals pass
       through the ionosphere.

       Received signals were processed using an autocorrelation function whose
       arguments are the time of a pulse and the pulse number.  There were 17
       pulse numbers for the Goose Bay system.  Instances in this databse are
       described by 2 attributes per pulse number, corresponding to the complex
       values returned by the function resulting from the complex electromagnetic
       signal.

    5. Number of Instances: 351

    6. Number of Attributes: 34 plus the class attribute
       -- All 34 predictor attributes are continuous

    7. Attribute Information:
       -- All 34 are continuous, as described above
       -- The 35th attribute is either "good" or "bad" according to the definition
          summarized above.  This is a binary classification task.

    8. Missing Values: None