Magnetization Solutions
Columns of the mag.txt files are:
Column 1:	projected distance along track (km)
Column 2:	depth to the top of the source layer (km) (sediment/basalt contact)
Column 3:	input magnetic anomaly  (nT)
Column 4:	inverted magnetization solution (A/m)
Column 5:	magnetic anomaly computed from the magnetization solution  (nT)




SouthTow Leg 2 near-bottom magnetics data
Columns of the mag.txt files are:
Column 1:	Index	
Column 2:	decimal hours	
Column 3:	Xpos	(m)
Column 4:	Ypos	(m)
Column 5:	fish	depth of the deeptow vehicle (m)
Column 6:	bath	depth of the seafloor (m)
Column 7:	Total field	(nT)


We removed rows with zero fish depth and zero total field values.

Information of scaling the X,Y position data in par.dat.txt to Lon.,Lat.:

We picked the origin at 52ºS, 121ºW.

It appears cos(51.0º) was used as the scaling factor for the X. 
This corresponds with the lat. of the center of the survey area (51ºS).

lon = -121.0 + Xpos/(111111*cosd(51));
lat = -52.0 + Ypos/111111; 

This matches the Lon,Lat from the SOTW02TW.mgd77 file well.

The Lon.,Lat. calculated from X,Y position data in par.dat.txt are smoother and offset
from the track lines in SOTW02TW.mgd77, leading us to think they are the wire corrected
fish track.

Used gmt to extract lon,lat from SOTW02TW.mgd77.
gmt mgd77list SOTW02WT -Flon,lat >ship_lon_lat.dat 