set xdata time
set timefmt "%H:%M:%S"

set format x "%H:%M"

### set term png
### set output "zimm20.png"
set title "ZIM20"
set ylabel "meters"
set xlabel "5-Dec-2009"

plot "ppp" u 1:4 t "dH" w p 3, \
     ""    u 1:2 t "dN" w l 1, \
     ""    u 1:3 t "dE" w l 2

pause -1