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-	BYU MERS Antarctic Iceberg Database		-
-		Jeff Budge, BYU Nov 2016                -
- w/revisions by D.G. Long, BYU Nov 2017                -
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This readme is intended to explain the contents the database.

FILES

Each file in the stats database contains information on one
named iceberg. The name of the iceberg is also the name of the file
with a .csv extension. The headers of each file show the date,
sensors, and sizes associated with that iceberg. A few notes:

-Each file has 9 columns, labeled in the first row:
 date,date_gap,disp,flags,lat,lon,mask,size,vel_angle

-Dates are shown in JD format, with the four digit year first followed
 by the three digit day of the year.

-The date_gap indicates the number of days between the current row and
 the preceeding row. Normally, this is 1 to provide daily iceberg
 positions; however, longer gaps occur due to missing and/or poor
 quality data.

-disp gives the approximate diplacement in km from the previous date
 entry

-The flags variable indicates which location values have been averaged
 into the reported value. This binary value includes a 1 or 0 in each
 bit position based on the sensors in the following order (starting
 from the LSB): 
 SASS, ERS, NSCAT, SeaWinds, QuikSCAT, OSCAT, ASCAT, NIC

-The nominal (averaged center position over all sensors) or
 interpolated position is given in decimal degrees in the lat and lon
 columns. Note that jumps in positions may occur when NIC and
 scatterometer positions differ.

-If the time and space gap between position reports is sufficently small
 (less than two weeks or 6 deg of longitude), daily interpolated 
 positions are provided.
 
-The mask variable indicates the surrounding ice/land conditions for
 the iceberg where 0=near land or no data, 1=sea ice, 2=open ocean,
 3=no data.

-The size gives the scatterometer-based estimate of the iceberg size
 on the particular date.  If the size could not be estimated, a value
 of 0 is shown.

-vel_angle gives the nominal angle in radians of the best-fit ellipse
 to the icebeg rotation angle.  Note that there is a possible 180 deg
 ambiguity.

-Standard NIC icebergs names begin with a, b, c, or d which give the
 origin quadrant. Additional icebergs were identified in scatterometer
 data; however, these unnamed icebergs are NOT included in the stats
 database.


KNOWN ISSUES

NIC positions are derived from NIC reports.  Some inconsistencies and
errors exist in these reports. NIC observation dates are irregular
and infrequent, especially in the early days, and are not interpolated
over long time or space gaps.  This can lead to jumps in the averaged
position when NIC reports differ from scatterometer observations.
