1) The DrillCalibration.dat file includes all drill hole results and
BH1 values. Range is the distance from the center stake along a given
transect line. Snow is from the MagnaProbe and drill is the ice
thickness from tape measurement. The draft and freeboard are ice
thicknesses above and below water level and should total to the drill
value. The BH1 value is the EM-31 reading at a certain height and
orientation. If multiple readings at the same station (often 4) then
Bruce took two measurements at surface and above surface perpendicular
to each other (for total of 4). These are real readings which show
sensitivity to these variables. These sensitivities are described in
the calibration section of the paper (section 2).

NOTE: The EM-31 thicknesses are not included in this file, only direct
measurements. Calibration holes are taken at 0.99m vertical offset
along the transect plus additional orientation measurements and
heights when possible. Calibration was also done at three of Bill
Simpson's stations which are called 8,9,10.

2) Composite file includes the final results that are used to plot
Figure 3 in the paper. The Helo thicknesses are linearly interpolated
from the original helo data set which should be archived separately (I
will check with Debi-Lee on that).

For completeness, I should dig through the original excel sheets that
Sarah Streeter finished up to identify exactly which Helo Lines were
finally selected. - NOTE TO SELF AND DEBI-LEE, I NEED TO DO THIS WITH
YOU!

3) The EM-31-derived thickness values in the composite file are
generated as follows:
 a) The BH1 values are used directly from the instrument (and listed
as the last column in this file as the raw data).

 b) the calibration is performed as per the paper (Figure 2) with the
calibration coefficients being those listed in Table 1 of the paper.

 c) From these calculations, the total thickness is computed which
includes snow+ice (but not instrument offset - this has been removed)

 d) the snow thickness is from the MagnaProbe (as described in the paper)

 e) the ice thickness is the total thickness just described minus the
snow thickness i.e., (c)-(d)

 f) if a drill hole measurement was taken along the transects, a 1 if
marked at the drill flag column. This value, the BH1 value, the line
number, and range are used to match up several of the calibration
drill holes with the transects.


Cathleen Geiger
Research Associate Professor
Department of Geography
College of Earth, Ocean, and Environment
University of Delaware
802-296-7279 (Main Office)
603-646-4851 (Alternate Office at CRREL)
cgeiger@udel.edu
http://www.udel.edu/Geography/geigerindex.html


Jackie Richter-Menge
Research Civil Engineer
Phone: 603-646-4266
Fax: 603-646-4644
E-mail: Jacqueline.A.Richter-Menge@usace.army.mil

USACE Engineer Research and Development Center
Cold Regions Research and Engineering Laboratory
72 Lyme Road, Hanover, New Hampshire, USA 03755-1290