Data Set Overview
  -----------------

    The electron reflectometry map of Mars consists of an ASCII file with
    latitude and longitude in bins of 0.5 deg.  This map is a derived
    data product; a number of assumptions went into its creation.  For
    details, please consult the following paper:

        An improved crustal magnetic field map of Mars from electron
        reflectometry: Highland volcano magmatic history and the end of the
        martian dynamo

        Robert J. Lillis, Herbert V. Frey, Michael Manga, David L. Mitchell,
        Robert P. Lin, Mario H. Acuna, Stephen W. Bougher

        Icarus 194 (2008) 575-596

        doi:10.1016/j.icarus.2007.09.032

    (To access the paper, go to the DOI website at http://dx.doi.org
    and type in the above DOI.)

    The ASCII map file in this data set is the same one used in the above
    cited paper.


    Data
    ----

    The contents of the map file are the elements of a 720 x 360-element
    matrix, i.e. 720 rows and 360 columns.  The spacing is 0.5 deg in both
    latitude and longitude.  The values of latitude are:

    -89.75 deg, -89.25 deg, -88.75 deg,...... -0.25 deg, 0.25 deg,...,
    88.75 deg, 89.25 deg, 89.75 deg.

    The longitudes are EAST longitudes and, from right to left, are:
    0.25 deg, 0.75 deg, 1.25 deg,..., 358.75 deg, 359.25 deg, 359.75 deg.

    In the file, the elements of the matrix are grouped into rows of six
    values each.

Confidence Level Overview
    -------------------------

  IMPORTANT NOTE:  ER-derived magnetic field magnitudes are NOT the same as
  magnetometer data and should NOT be treated as such.  Users of the data are
  strongly advised to contact Dr. Robert J. Lillis, the provider of the map,
  before using the data in publications.