Re: trajectorie plot

[Mick Spillane <spillane@xxxxxxxxxxxxx>]

Hi Michael,
	I've cut and pasted your data into an ascii file and read it into
ferret.  The longitudes start at 166.8E, decrease to 88.0E then increase
again, crossing the Greenwich between points 28 and 29 before ending at
17.9E = 377.9E.
	If this is correct then you need to add 360 to the last two points
to preserve the order:

def axis/t="2-jan-1978:00:00":"31-jan-1978:00:00":1/units=days tax
def grid/t=tax grd
file/form=(20x,f7.1,f7.2)/var=lon,lat/g=grd traub.d
let newlon = if lon lt 50 then lon+360 else lon
! I just chose 50 as a point where the trajectory never goes
! Then to plot the trajectory and confirm the sequence
plot/vs/line=2 newlon,lat
repeat/L=1:30 (label `newlon` `lat` 0 0 0.1 @sr`L`)

To overlay it on a chart continue as follows
use etopo20
shade/lev=(0.9,1.1,0.2)/pal=grey/nokey if(rose[d=2] ge 0) then 1
set data 1
plot/vs/line=2/o newlon,lat
repeat/L=1:30 (label `newlon` `lat` 0 0 0.1 @sr`L`)

I realize that this is not a general solution. If the trajectory were to
wrap complete around the globe one or more times one would have to be
more clever with the "newlon" transformation, or do it in a piecewise
manner.  But it should be possible to preserve the order of points along
the trajectory.

Good luck,
Mick

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