rendering scattered data

[Lorenzo]

Hi all,

I've got a program providing a graphical output consisting in 2D
scattered data over a map, coloured in such a way to give me some sort
of time-information.

Of course, I use the following instruction to plot it:

scatter(longitude,latitude,3,time_info,'filled')

These vectors can easily be of one hundred thousand components.
Problem rises when I try to save the output image as a .TIF file,
since the saveas function takes an awfully long time (i'm talking
about hours): I used the profiler and found out that, apparently, the
problem dwells in the renderer, specifically in the following line
(line 100 of function "print")

pj.Return = hardcopy( inputargs{:} );

Tried to change the renderer, from "painter" to "openGL" (hardware)
but execution times were always enormous...

Can anybody please propose a solution? Please keep in mind I would
need a loseless graphical output (.jpg or .bmp are not an option).

Thank you very much in advance

lor