set grid
set datafile separator ","
#set key top right
#set key box
set title "RV G.O Sars Survey July 2008\nPlot of depth [logged (1 min interval) and interpolated (10 s interval)]\
 and ship speed as function of survey day #\n"
set xlabel "Survey day #"
set ylabel "Depth [m]"
set xrange [2:3]
set yrange [-3500:500]
set y2label "Ship speed [kt]"
set y2range [0:16]
set y2tics border
set y2tics 0,2,16
plot 'navdata-stage-1.txt' using (($1-1214807740)/86400):(-$8) with points lt 1 title "Depth logged",\
 'navdata-stage-1.txt' using (($1-1214807740)/86400):9 with line lt 2 axes x1y2 title "Ship speed",\
 'gravdata-final.txt' using (($1-1214807740)/86400):(-$6) with line lt 3 title "Depth interpolated"