[ferret_users] mp_polymark without grid data

[Hella Riede <riede@xxxxxxxxxxxxxxxxx>]

Dear Ferret users,

I am trying to plot trajectories in stereographic north projection.

In the email archive, I found the following link:
http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2003/msg00729.html,
which gives an example, which also works in the adapted form here:

use coads_climatology
go mp_stereographic_north
set grid sst
go mp_aspect
set region/x=0:360/y=00:90/l=1
shade/noaxis sst, x_page, y_page
use polydata
go mp_polymark poly/over/noaxis/key lon lat sst star 0.5


However, I would like to plot data in stereograhic mode only with
polymark, where longitude, latitude and the polymark color variable
"pressure" are defined as xsequences. Is there a way to do that on a
predefined map (such as seen in mp_land) in stereographic north without
using any gridded dataset?

When I don't quit ferret and then try to plot with mp_polymark alone
from the above sample, the graphics are shifted in a strange way.

Thanks in advance for any help.

Regards,
Hella